HINDUSTAN PETROLEUM CORP. LTD.MUMBAI REFINERY

HAND BOOKON

“PUMPS, EXCHANGERS & FIRED HEATERS”

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Preface

Amongst various types of unit equipment used in operating units, Pumps, Compressors, Exchangers & Fired Heaters forms a part of most trouble shooted equipment. Moreover, most of these failures are attributed to delayed responses or bad operations. Such failure not only involves expensive repairs but also results in interruptions in production or generation of off spec products, slippage of delivery schedules etc.

With this in mind, an effort has been made in the form of a ready reference hand book which is expected to provide guidance to operating personnel while handling unit facilities. The details given in this hand book is prepared after thorough review of various unit activities & also has considered the existing procedures adopted and followed by different operating units in our Refinery. This manual is expected to be very useful to all operating personnel who already have greater understanding & experience in operation, trouble shooting in processing units of our refinery. The main intent is to enable operating personnel to carry out trouble shooting with greater accuracy as & when they arise.

I have great pleasure in introducing this hand book prepared by Shri R R Iyer & Shri A V Oak, who have a wide experience in Operation, trouble shooting of existing units & also have taken lead roles in commissioning/decommissioning of several new facilities of units in our refinery. I am confident that this book would enable our operating personnel in operating units safely specially while trouble shooting of our unit equipments.

N S J Rao General Manager, Operations - MR

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MUMBAIDecember 01, 2009.

INDEX

Sr. No. Topic Page No.

1. Pumps, Types of pumps 5

2. Pumping Terms and Definitions 8

3. Double Mechanical seals – What happens if? 11

4. Check list for commissioning of Pumps: 12

5. Dos & Don’ts: Centrifugal pumps 14

6. Dos & Don’ts: Reciprocating pumps 15

7. Check list for Hot Service Pumps 15

8. De- Commissioning & Handing over for Repairs 17

9. General trouble shooting checks on pumps. 18

10. Handing over of hot service pumps for M &R 20

11. Change over of Furnace feed pumps 22

12. Change over of gas Compressor Lube Oil pumps: 22

13. EQUIPMENT CHECK LIST- PUMP

1. Commissioning of pumps after maintenance job 24

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2. De-Commissioning of pumps for maintenance job 25

14. Daily checks during Regular Operation of Pumps: 27

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An introduction to

“PUMPS”

PUMPS

Pumps provide a means of adding energy to a fluid in order to have the capability of transporting the fluid from one level of potential and kinetic energy to another. Depending on a multiple of parameter, various means of adding the energy are employed. Energy can neither be created nor be destroyed; it can only be transformed from one form into another. Energy can be classified as Mechanical Energy, chemical energy, heat energy, Hydraulic energy, Nuclear energy etc. In a pump the mechanical energy is being converted to Hydraulic energy. Hydraulic energy again can be reclassified as Pressure energy, Velocity energy (Kinetic) and Potential energy.

Pressure energy : Energy owing to pressure of liquid.Kinetic energy : Energy owing to velocity of the liquid.Potential Energy : Energy owing to head of liquid.

Type of Pumps

Pumping Terms and Definitions

Pumping is the addition of energy to liquid to move it from one point to another.

Reciprocating Pumps use pistons, plungers, diaphragms or other devices to displace a given volume of liquid during each stroke of the unit.

Liquid piston or plunger of a reciprocating pump is the moving member that contacts the liquid and imparts energy to it.

Simplex reciprocating pumps are those which are equipped with only one liquid piston or plunger.

Duplex or Triplex reciprocating pumps are equipped, respectively with two or three liquid pistons or plungers.

Single- Acting reciprocating pumps produce only one suction and one discharge stroke per cycle.

Double- Acting reciprocating pumps produce two suction and two discharge stroke cycle.

Surge Chamber are containers built into a reciprocating pump or attached to its adjacent piping to cushion the shock of the reciprocating action and, therefore, smoothing the liquid fluid.

Centrifugal Pumps employ centrifugal force to develop a pressure rise for moving a fluid.

Impeller is the rotating element in a centrifugal pump through which liquid passes and by means of which energy is imparted to the liquid.

Casing of centrifugal pumps is the housing surrounding the impeller. It contains the bearing for supporting the shaft on which the impeller mounts.

Single-Stage centrifugal pumps is one in which total head is developed by one impeller.

Multi-Stage centrifugal pump is one having two or more impellers acting in series in one casting.

Critical Speed of a centrifugal pump is that speed at which the rotating shaft corresponds to its natural frequency. At this speed any minor imbalance of the shaft is magnified and excessive vibration will occur.

Rotary Pumps use gears, vanes, pistons, screw, cams, etc. in a fixed casting to produce positive displacements of a liquid.

Packing is any material used to control leakage between a moving and stationary part in the pump.

Mechanical Seals are devices mounted on the shaft of centrifugal pumps to seal in the casing. These are frequently used in preference to packing because of their longer life and minimized leakage.

Cavitation is the phenomenon caused by vaporization of a liquid inside pump. When the pressure at any point drops below the vapor pressure corresponding to the temperature of the liquid being pumped. Vaporization of the liquid will occur. Small cavities of vapour thus formed move with the flow through the pump until a region of high pressure is reached. The higher pressure causes the vapour cavities to collapse with tremendous shock on the surrounding metal.

Viscosity is that property of a liquid that resist any force tending to produce flow.

Specific Gravity of a liquid is that number which denotes the ratio of the weight of the liquid to the weight of an equal volume of water.

Suction Lift exists when the source of supply is below the center line of the pump.

Static Suction Lift is the vertical distance in feet from the center line of the pump to the free level of the liquid to be pumped.

Total Dynamic Suction Lift is the vertical distance in feet from the center of line of the pump to the level of the liquid to be pumped plus all friction losses in the suction pipe and fitting.

Suction Head exist when the source of supply is above the center line of the pump.Static Suction Head is the vertical distance in feet from the center line of the pump to free level of the liquid to be pumped.

Total Dynamic Suction Head is the vertical distance in feet from the center line of the pump to the free level of the liquid to be pumped minus all friction losses in suction pipe and fittings.

Net Positive Suction Head –(NPSH) required is the energy needed on the suction side of a pump to fill the pump to the discharge valve during operations.

Shaft Sealing

In general, centrifugal pumps have mechanical seals. A mechanical seals has a rotating face and stationary face. Numerous means such as bellows, wedges, and O-rings are used to seal the rotating face (seal head) against the shaft sleeve. O-rings are normally used to seal the stationary face (seat) to the casing. In some cases, larger face with the spring is held stationary and the other face rotates (rotating seat). The rotating face and the stationary face are mechanically smooth and matched so they fit together perfectly.

The stationary face is many times made of carbon and the rotating face of stainless steel. the seal head is driven by a spring or spring- loaded pins. It rotates with the shaft and held against the stationary face by spring pressure.

Mechanical seals are available as either internal or external, balanced or unbalanced, single, double, or tandem, to name some of the variables which must be considered. Figures show typical single mechanical seals.

Various flushing and cooling schemes are available to combat various environment that are hostile to the mechanical seal face integrity, elastomers, etc.

Usage of tandem and double seals is on the increase due to more stringent environment regulations. Currently any hydrocarbon service with high vapour pressure or high concentration of benzene, hydrogen sulfide of aromatics requires tandem seals.

NPSH

NPSH is the net head available at the eye of the impellor of the pump. This is calculated based on the system head available at the suction of the pump minus the vapour pressure head of the liquid at the operating condition. Thus the difference in the suction head and the vapour pressure head is called `Net positive suction head’ or NPSH Pumps cavitate because they lack sufficient available NPSH ie. the available NPSH is lower than the required NPSH.

Cavitation

Double Mechanical seals – What happens if?What happens when primary seal fails and secondary seal is intact??The level in the seal pot will start increasing as the process fluid will go in the pot. Slowly, the pressure in the pot will increase and the PG on the seal pot will show a high reading (equal to the discharge pressure of pump).What happens when primary seal is intact and secondary seal fails??The Seal pot level will drop and will become empty.

Centrifugal pumps – Important pointsThe suction valve should always be wide open. Throttling the suction valve reduces the available NPSH.Discharge valve should be almost shut while starting the pump. This is because the pump capacity with discharge valve shut (shut off head) is Nil, there by requiring minimal power. Starting the pump with discharge valve wide open, will trip the motor on over load.Minimum flow through the pump should always be ensured.Prime the pump before start. Ensure continuous flow of seal oil. The mechanical seals require a liquid seal material to keep the seal faces from touching each other and rubbing.

Positive displacement pumpsAs the name `positive displacement indicates that this pump ensures displacement of the liquid unlike centrifugal pump, where the pump may be running but need not necessarily be displacing liquid. This pump ensures pumping of liquid at the required pressure. This pump is normally used when capacity to be pumped is low and head required is high.  

Positive displacement pumps – Important points

The suction valve should always be wide open. Discharge valve should be wide open while starting the pump. If the pump is on with discharge closed, it will develop

excessive pressure to pop the safety of the pump. Ensure that the safety valve on the pump discharge is in line.

Check list for commissioning of Pumps:

Check for proper necessary piping connection has been made. Cooling water lines to stuffing boxes, bearing jacket pedestals and quench glands should be connected and operable. Check that the drive rotates freely in the direction indicated by arrow mark on casing and ensure protection by coupling

guard. Check for bearing housing oil level and quality. Check seal system of pump is commissioned. Check instruments and pressure gauges. Check that all bleeder valves on s/c and d/c are closed. Ensure that motor is properly earthed. Bring the pump to its service stream temperature. If the pump is in hot oil service, it should be gradually warmed up to a temperature close to that of the handled fluid.

This is absolutely necessary as otherwise the pump casing and the impeller are likely to be damaged due to the thermal shock.

Starting the pump: Prime the pump, by opening bleeder valve of pump casing or d/c side PG drain. (Except for vacuum

service pump). Start seal oil to the pump Open cooling water to the pump. Close d/c valve and start the pump in case of CF pump. In case of PD pump, open discharge valve. After starting the pump check for d/c pressure. If no pressure rise is observed then stop the pump and

ascertain the cause. If d/c pressure is satisfactory, slowly open the d/c valve till desired flow and pressure is reached. Look for abnormal conditions (hot stuffing box, excessive vibration or noise, high bearing

temperature of pump/motor and abnormal oil losses). If pump is running satisfactory, check for amperage taken by the motor.

Procedure for stopping the centrifugal pump: Slowly close the discharge valve of the pump. a. Stop the motor if the pump is motor driven.b. When shaft comes to a halt, close the suction valve.c. If the pump is to be handed over to maintenance, stop the seal oil and cooling water after the pump has been

cooled down.

Daily checks during Regular Operation of Pumps: Check for cooling water, seal oil system and Gland condition. Check bearing of motor and pumps. Check bearing housing oil level and oil should be free of water. Check the lube oil to be sure of right lubricant Replenish oil in oil cup when ever found empty. Flush the bearing oil if found contaminated. or stop the pump &inform rotary section Don’t try to start the pump if it is found jam Check for Pressure gauge reading to ensure pump is running ok. Check for Abnormal noise and Vibrations. For turbine driven spare pumps the shaft should be kept slowly rotating. Insulated work gloves when handling hot bearings or using bearing heater.

Never operate pump without a coupling guard properly installed. Do not operate below minimum rated flow, or with suction/discharge valves closed. Do not open vent or drain valves, or remove plugs while system is pressurized. Touch the bearing housing and try to hold for minimum five sec. If not able to hold, then temperature

is in alarming range.Dos & Don’ts: Centrifugal pumps

A idle pump without checking for adequacy of Lube Oil in bearing, Without checking freeness by turning the pump by hand, or by mechanical levers. Never attempt manual rotation or turning of pumps with switch on AUTO mode or a pump with remote start

facility, Never start a pump without adequate earth protection, Never attempt bearing oil changing without stopping the pump. Never allow use of solvent cleaning of hot casings of pump. Never allow dry run on any pump, Never start the pump without coupling guards. Never allow any Mechanical activity without De energizing the pump. Never start any pump without knowing the fluid property, Never start a high tension motor without obtaining clearance from shift electrical. Never start any pump without reconfirming the suction / discharge, seal flushing, BCW line-ups. Track the amperage data – it reads a story about pump fitness. Any increase in amperage easily correlated to

increased loads & unknown load reason can be traced by further EED analysis for balance life of bearing, defects on impellers.

Dos & Don’ts: Reciprocating pumps

Keep the s/c & discharge valves wide open, never operate these pumps with throttled block valves. Always ensure availability of safety valve, keep them service. Periodically check discharge line pulsation dampeners. Check the thoroughness of discharge line-up prior to starting the pumps. Put the spill back control in service, keep them under proper check. Keep a close watch on discharge pressure, Periodically inspect Suction strainer & take up repairs as when required & regularly clean.

HOT SERVICE PUMPS

COMMISSIONING:a) Initial checks: After maintenance job on pump following things to be checked before commissioning the

pump-A) Electrical motor and pump installed on its foundation, all foundation bolts are tightened. Cable

connections are made and electrical personnel check motor rotations and again the breaker is de-energized.B) Pump cold alignment has been done. C) Bearing CW and Seal oil lines connected, seal oil strainer / R.O cleaned, Bearing CW lines are clear.D) Pump Suction strainer if required is cleaned and boxed up properly, its drain line is clear.

Drain lines are extended up to close sewerE) Pressure gauge of appropriate range on Pump discharge is installed.

b) Warming up: -A) Fill up the pump casing with seal oil or flushing oil (if provided on Pump Suct. Line). Make sure that Pump Suct.

And Dish. Lines are filled up, up to the isolation BVs, air and condensates are removed. No leaks on the flanges which were opened for repairs.

B) Commission bearing CW to the pump. C) Inform DCS control room Supdt. About the pump warming up. Pump has to be warmed up, very gradually and

finally to be made hot up to the normal operating temp. Open pump warm up line BV slowly and displace the light oil by draining at pump Suct. Keeping drain BV throttled to maintained positive press in the pump so as to avoid formation of air / vapour pocket in the pump casing or in the line up.

D) Once the light oil is displaced, close drain BV and warm up line BV, partially open Suction. BV and gradually open warm up line BV. Check that liquid flow is established through warm up line to pump Suct.

E) Slowly open the Suct. BV and make it wide open keeping watch on the running pump and the flow. Commission the seal oil to the pump.

F) Get the hot alignment and coupling done.

Starting the Pump: - As far as possible pump to be started in the presence Machinist first time after the pump repairs.A) Get the breaker energized, inform DCS control room Supdt. About the pump start up

and get O.K from him.B) Ensure Suction BV is wide open & seal oil is commissioned. Partially open the dish. BV

and start the pump. Observe the Dish. Press, flow and pump load, Open the dish. Valve slowly keeping watch on the pump dish. Press, AMPS (load) and flow. Stabilize the pump operation.

C) If recirculation line is provided commission the same. D) Inform machinist to check vibration readings.

DE-COMMISSIONING AND HANDING OVER FOR REPAIRS: -

If pump is to be handed over to maintenance for repairs due to seal leak, jammed or any other problem, then the pump has to be isolated/ depressurized/de-energized.

A) Isolating the pump: 1. If the pump is in service, inform DCS Supdt. About the pump to be spared. Gradually reduce load on the pump. Stop

the pump when disch. BV is closed. Maintain the process flow by increasing load on the spare pump simultaneously. 2. Block Dish, Suct. BVs and warm up line BV tightly, also block seal oil to the pump. Allow the pump to cool

sufficiently. Get the drain line on Suct and dish extended up to close sewer.3. Depressurize the pump, if required tighten the isolation BVs and warm up line valves ensure the isolation BVs are

holding. Flush the pump with light oil / seal oil if it is in viscous fluid service.

B) Removal of pump:1. Get the breaker de-energized and tagged in the field at the local Push button & breaker panel, also confirm the same

by pressing the ON the push button.2. Hand over the pump to Maintenance to carry out repairs. If the pump is removed to shop get the Suct. And Dish.

Lines open ends blind flanged. Maintain process stand by during pump removal.

Note:-1. Ensure that spare/ stand by pump warm up line is open and pump is hot. Appropriate quantity of seal oil to

the pump is open, preferably seal oil line have R.O or Rota meter. Maintain seal oil header pressure normal all the time.

2. Commissioning and de-commissioning procedure for the cold oil service pump is similar to hot oil service pump, except light oil filling/flushing and warming of pump. Pump to be filled up with the process fluid to remove air/ vapour pockets and primed properly before starting the pump.

General trouble shooting checks on pumps.

Sr no

Trouble Possible cause

1. Liquid not delivered, flow is fluctuating Pump is not primedCavitations, vapour lockWrong direction of rotationLow RPMImpeller or the the discharge line in clogged

2. Failure to deliver rated capacity & insufficient discharge pressure

NPSH not sufficient

Pump RPM is lowWrong direction of rotation

Impeller damaged, or clogged. Vapour lockingViscosity / Sp. Gravity not as per spec. Air leak in stuffing boxBack pressure is high in discharge header.

3. Pump loses prime RPM is too high, Vapour lockAir leak in stuffing box

4. Pump over heats driver Speed is too high Misaligned Total head lower than rated head. Low voltageLoss of lubrication

5 Pump vibrations NPSH not sufficient

Vapour lockMisaligned Bearing is worn outFoundation is not rigid.Minimum flow requirement is not met. Impeller clogged. Cavitation

6. Stuffing box is overheating Packing too tight.Insufficient lubricationIncorrect packingGland is cocked

7. Bearing is over heating rapidly. Excessive oil in bearing house Or no oil in Bearing house. Misalignment of pump, line stresses, Insufficient cooling water flow.Oil ring not functioning.NPSH deviation is high than specified. Improper lubricationVibration

Handing over of hot service pumps for M & R:Following are the guidelines required to be known while executing this job:

Steps involves in handing over the jobShift the load to the stand by pump.Steps: Check stand by pumps freeness of the pump by physical rotation .Commission seal oil, seal oil bearing cooling water ,check and confirm flows ( if LP steam is provided for

seal flushing thoroughly drain condensates and re-control the proper operations of seam traps).Confirm wide opening of suction valve. Remove vapour lock through discharge bleeders.

Check and control isolation of all drains and vents. If necessary install plugs or caps.Seek electrical permission incase of high tension motors.Start the pump. Check the discharge pressure, (is expected to be greater than the pump in service). Slowly open discharge block valves of pump to be pressed in service while throttling discharge block

valve of pump previously in service & continue this load shifting till discharge block valve of pump in services is fully shut & pump to be shifted in service is sufficiently open to meet the

required load & then stop the pump which was in serviceTake confirmation on flow adequacy from control room and amperage through electrical and if normal

stop the pump which was in service. Wait for 15 to 20 minutes to fully assess the healthy ness of pump performance, and then proceed to next step 2.

2 Isolate warm up connection ,warm up, seal flushing ( external seal ) , isolate suction discharge ( double isolation whenever provision exist) , BCW ( carry out light oil flushing for pumps handling , congealing fluids).

3. De-pressuring & confirmation for passing valves.Isolate pump suction , discharge block valves, slowly open discharge line drain and empty the residual pressure till no liquid or vapour seen no liquid or vapour seen at the drain and the pressure gauge is zero. Wait for few minutes to make an observation for passing valves.Note: Nominal passing of valves will through liquid vapour, vapour intermittently into the drain, if the valve is passing more continuous flow would be visible at the drain , if the valve is severely passing liquid drain flow will be of high velocity. Simultaneously in case of vacuum at suction sucking of air through discharge bleeder can be observed.

Considering the above steps 1,2 & 3 –If the leak persist, even after all possible isolations have done and reconfirmed, seek advice of supervisors help prior to proceeding to the next step.

4. De-energize the motor.

Follow the permit procedure for de energizing and confirmed the motor is de-energized through field verifications.

5. Motor termination if the motor to be removed.Allow motor termination only if motor is confirmed de-energized- wiring to be secured by insulations.

6. Blinding; suction, discharge, warm up, seal oil , flushing oil,

Considering the valves are holding as confirmed the step above issue permit of blinding of suction , discharge, seal oil, flushing oil, flushing steam, bearing cooling water, headers, once all blinds are in place allow removal of pump after draining the residual oil in the casing

7 DiscouplingIssue permit for the discoupling

8 Hot or cold permit for removal to workshop.If pump- shifting require use of fork lift or Crane issue hot work permit for Crain operation and for pump removal. Cold permit l is only for physical lifting removal of pump without use of Crane or forklift.

Change over of Furnace feed pumps:

Pump change over though appear a very normal event considering availability of stand by pumps, a feed pump catering to a furnace flow needs is a critical operation. The field personnel must clearly understand the implication of loss feed, low flow to heaters. Such loss of flows will have very adverse effect on unit stability; add to further critical operations like furnace reset, re commissioning besides loss of production & loss of product quality. Hence detailed checks prior to such changes must be followed rigidly & systematically.

Change over of gas Compressor Lube Oil pumps:Though this activity is very normal change any other unit pump the operator must understand the criticality and

implication due to loss of lube oil pressure. Such losses will result in tripping of compressor due to actuation lube oil and seal oil Low pressure switch. Typically lube oil pumps are centrifugal pumps or screw pump, incase of centrifugal pumps follow normal procedure for change over. In case of turbine drive of stand by lube oil pump follow procedure as given below:

A) Speed governor system:

Speed governor system is used for (1) to control load automatically, (2) to measure shaft speed and adjust governor valve opening to pass the needed steam flow.

Fly ball governor is used in this turbine. The over speed trip system consist of the over speed sensing device, the inter connecting linkage between it and a trip valve.

The over spread sensing device includes those elements which are directly responsible to speed and which initiate action to close the trip valve at a pre-determined over speed i.e. trip speed.

B) Normal Operation:

(1) The initial start up should be in uncoupled from the driven unit.

(2) Rotate turbine manually and check for freeness of rotation.

(3) Open drains - turbine casing, steam chest, steam ring, inter stage and exhaust, turbine stop valve, and line drains of steam inlet and exhaust.

(4) Start warming. Allow pressure to build up to turbine stop valve.

(5) Open cooling water supply.

(6) Verify turbine Governor is at low speed stop setting.

(7) Manually crack open the turbine stop valve to turn the rotor slowly.

(8) Check the trip manually and check rotor speed it should reduce. If it is ok reset and start the turbine rotor slowly. Maintain low speed. Check all bearings and continue low speed to warm up the oil to 35°C.

(9) Slowly increase turbine speed. Check for Vibrations.

Start Up:

(1) Check oil system for leaks, check cooling water, and check steam drains and traps.

(2) The turbine can be coupled to the driven unit.

(3) Next procedure is same on above.

(4) The emergency trip valve assembly consists of trip and trip valve which is actuated by a spring loaded piston. Normally the emergency trip valve remains in a fully open position. Inlet steam passes through this valve to the governor valve, when trip valve is actuates all steam flow is shut off. Upon release of the head lever by the emergency tappet the trip lever rotates the trip shaft. This releases the spring piston and the emergency trip valve snaps closed.

EQUIPMENT CHECK LIST- PUMP

JOB DETAILS: COMMISSIONING OF PUMP AFTER MAINTENANCE JOB

SN Particulars of Checks1 Pump Suction and Disch lines checked, isolated and depressurized.2 Blind flanges on the Suction and Dish. lines

Removed in presence of Process area technician3 All nut and bolts installed on Flanges. Seal oil, BCW lines, ECS

vapour disposal lines etc. are connected after Pump installation4 Cold alignment job done 5 Seal Oil strainer cleaned6 Electrician checked the rotation of motor and again de energized the breaker..7 DCS panel officer informed8 Pump is filled up with cold light oil and Checked for no leaks.9 PG of suitable range is available on the Pump discharge.10 Pump is warmed up (if hot service) & hot alignment done11 Seal oil (if external seal) & BCW to pump commissioned12 Coupling job done, shaft free rotation checked. Coupling guard is installed and fixed properly.13 Lubricating oil is filled and the oil level in L.O cup is OK.14 Electrical supply to Motor Energized in Sub Station.15 Local Panel switch precautionary tags removed 16 Pump trial taken in presence of Machinist as required.

EQUIPMENT CHECK LIST- PUMP

DECOMMISSIONING OF PUMP FOR MAINTENANCE JOB

SN Particulars of Checks

1 DCS panel officer informed about the pump to be spared.2 Electrical Supervisor informed ( for HT Motors)3 Stand by Pump is healthy 4 Stand by Pump started and performance observed for sufficient

time. 5 Pump to be handed to maintenance is spared.6 Pump Isolated:

a) Suction valve closedb) Disch. valve closedc) Warm up line blockedd) Seal oil line closede) ECS to BDD isolated ( if Seal is ECS)f) BCW line isolated

7 Pump cooled down to safe temperature (if hot oil service)8 Pump content drained and pump is depressurized completely 9 Isolation valves are holding confirmed10 Pump is flushed with light oil (applicable if Viscous or Corrosive

Liquid service)11 Electrical supply to Motor de-energized in Sub Station.12 Power supply cut off tagged in field and on

the breaker panel in Sub-station.13 Local Panel switch tagged properly after confirming Power

supply cut off. 14 Pump is handed over for removal and Permit is issued15 Pump is removed and open ends of all connecting hydrocarbon

Lines are blinded properly. House keeping done.

Daily checks during Regular Operation of Pumps:

Check for cooling water, seal oil system and Gland condition. Check bearing of motor and pumps. Check bearing housing oil level and oil should be free of water. Check the lube oil to be sure of right lubricant Replenish oil in oil cup when ever found empty. Flush the bearing oil if found contaminated. or stop the pump &inform rotary section Don’t try to start the pump if it is found jam Check for Pressure gauge reading to ensure pump is running ok. Check for Abnormal noise and Vibrations. For turbine driven spare pumps the shaft should be kept slowly rotating. Insulated work gloves when handling hot bearings or using bearing heater. Never operate pump without a coupling guard properly installed. Do not operate below minimum rated flow, or with suction/discharge valves closed. Do not open vent or drain valves, or remove plugs while system is pressurized. Touch the bearing housing and try to hold for minimum five sec. If not able to hold, then temperature

is in alarming range.

LPG Pump commissioning procedure: The following step by step procedure shall be adopted for commissioning a pump.

1. Ensure that all the jobs are completed on the pump.2. Seal vapour disposal line is commissioned and lined up to flare.3. Pressure switch is in line and pressure alarm setting is kept 0.5 kg/cm2 higher than closed flare header pressure.4. Presence of pressure gauge on vapour disposal line.5. In case of ECS seal, the secondary seal is a dry gas seal. In case of Primary seal failure the Pressure at the Secondary Seal increases and sensed by the pressure Switch which gives an alarm in DCS. Primary Seal failure may be confirmed by checking pressure on Pressure Gauge of the vapour disposal line.

6. Ensure that the blinds are open on suction and discharge lines of the pump.

7. Ensure that the rotary and electrical groups are present at the site.

8. Ensure that the pump casing vent connected to flare line blind is removed.

9. Open the pump casing vent and bleed off the air trapped in the pump casing.

10. Slowly open suction and discharge valves and observe the rise in pressure.

11. Start the pump and circulate a sphere using the pump for one hour.

Light hydrocarbon pumps (LPG, propane):

1. Check free rotation of the pump before starting the pump2. Ensure designed suction pressure and pump is properly primed before starting3. In case of ECS (double mechanical seal), ensure vent is connected to flare line with a NRV, pressure

alarm is hooked up at control room. Check local pressure gauge on vapour disposal line for any pressure rise.

4. In case of pressure rise/pressure alarm, inform rotary for check.5. Don’t run the pump if product is leaking to atmosphere from any sealing area6. In case of tandem seal with seal pot lubrication at outer seal, check the oil level and alarm of level

switch must be hooked up at control room. In case of alarm, check for high level at field and inform rotary for further checks.

7. In case pump is jam due to ice formation on mechanical seal (happens due to throttling expansion of gaseous LPG/propane to stuffing box when pump is idle), treated water may be put from outside on gland follower to remove the ice inside.

8. Don’t try to start pump if it is found jammed.

General Instructions:1. Carry out proper priming of the pump before start2. In case of vapor lock, stop the pump and prime it again before restarting3. Routine change over of service to standby pump enhances bearing/seal life.4. Check for free rotation, cooling water system& lubrication before start up.5. Monitor running equipment parameters at least twice in a shift.

Basic design“Compressor”

INDEX

Sr. No. Topic Page No.1. How Centrifugal pumps works 31

2. Multi-stage Centrifugal Compressors 31

3. Journal Bearings 34

4. Axial Thrust 34

5. Surge 34

6. Wet Gas Compressor (WGC) 34

7. Reciprocating compressors 35

8. Propane compressor C-302 –start-up in propane dewaxing unit - LR 38

9.Stripping Gas start up C502 start-up for SEU’s in LR 41

10. EQUIPMENT CHECK LIST- WET GAS COMPRESSOR

1. Commissioning of Wet Gas Compressor 42

2. De-commissioning of Wet Gas Compressor 45

11. Procedure for starting C-9 compressor 46

12. Procedure for stopping the compressor 47

How Centrifugal Compressor works: Centrifugal compressor and Centrifugal pumps work on the same principle. Both are dynamic

machines converting velocity into head. The gas enters the compressor’s rotor through the large wheel (as shown in picture). The purpose of

this wheel is to increase the velocity or Kinetic energy of the gas. After the high velocity gas escapes the vanes in the wheel, the gas enters the stationary elements fixed to

the inner wall of the compressor. This converts the Kinetic energy of the gas to polytropic head.

Multi stage Centrifugal Compressor: In practice, the pressure increase from one impeller is not sufficient for most of the process

requirements. Hence, for large pressure differentials, several impellers are mounted on the common shaft and the discharge from one impeller is led to the suction of the next impeller.

Number of impellers in one casing is limited by the temperature increase which accompanies compression.

Each impeller is a compression stage so that when several impellers are used, the compression is known as multi stage.

The first stage impeller is normally the widest and each succeeding impeller is smaller.

Journal Bearings:

The journal bearings support the weight of the rotor. It requires continuous pressure lubrication to cool the bearing and prevent metal to metal contact.

It is essential that the center of gravity of the rotating assembly lies on the center line of the rotating shaft. Else, the centrifugal action produces excessive radial force, which causes the rotor to vibrate in the bearings. This can cause bearing failure.

During continuous operation, partial bearing failure may occur due to over heating causing increased bearing clearance, thereby increase in vibration. Hence, cooler outlet temperature to be monitored.

Axial Thrust: The compressor at each impeller stage produces a differential that is applied across the impeller front

and back cover areas. The net result is a main axial force pushing the rotor towards the suction end of the compressor casing. This main axial force is counteracted by a reverse axial force produced across a Balance piston located

at the discharge end of the compressor casing. The other side of this Balance piston is connected back to the suction pressure by a balance line.

What is surge?

What is actually happening inside a compressor when it begins to make that surging sound? When a compressor starts to surge, the gas flows backwards through the rotating assembly. This pushes

the rotor backwards. The rotor slides backwards along its Journal bearings. The end of the rotor’s shaft now slams into the thrust bearing. The thrust bearing constrains the axial

(horizontal) movement of the rotor. Each time the rotor surges, the force of the end of the shaft impacting the thrust bearing causes the

thrust bearings to deform.

Wet Gas Compressor (WGC):

Clark Gas compressor is a horizontally split centrifugal 5 stage compressor. The main duty of this compressor is to compress gas from the Fractionator’s over head drum for

recovery of C3, C4 and C5 component. Rotor assembly mainly comprises of a shaft on which are mounted the impellor, thrust bearing and

coupling hub. The labyrinth seal limits gas leakage between discharge and intake pressure areas of impellers. Thrust bearing and Journal bearings are lubricated by lube oil at 20 psig pressure.

Reciprocating compressors:

A Reciprocating compressor is a direct volume- reduction machine. The gas is simply squeezed out of a cylinder by a piston and pushed into the discharge line. The molecular weight of the gas does not influence the suction or discharge pressure of the compressor. The gas density does not influence the compressor performance or the work required by the driver.

The reciprocating compressor is a positive displacement compressor. It is cheaper to purchase and install than a centrifugal compressor. Also, in theory far more efficient (90 percent) than a centrifugal compressor (70 percent). Certainly, reciprocating compressors are simpler to understand and engineer than centrifugal machines. Best of all, they are not subject to surge.

There are only two real problems with reciprocating compressors pulsation and mechanical reliability. But these problems are so untraceable that; for most industrial applications, centrifugal compressors are preferred, the exception is when dealing with low- molecular- weight gas. A low- molecular- weight gas, like hydrogen, has a low density. Let’s say that a compressor must develop a large differential pressure.

Important points:

Ensure adequate supply of LO to the compressor at required pressure. Switch over the LO filters at regular interval. Drain the suction before start of compressor to ensure no liquid carryover to the compressor. Pull vacuum in the suction prior to start of the compressor, to ensure no leakages. See compressor wise start-up or shut down procedures / check list. Never deviate the sequence of check list as these have very serious repercussions.

Propane compressor C-302 –start-up in propane dewaxing unit - LR

Check list for C302 START-UP

Field:

S/N Activity

1. Stroke the suction PC318, recycle FC328, and suction temperature controller TC318.

2.Before starting, keep FC328 in Manual mode (25-30% open), PC318 in Manual mode (30% open). Keep TC318 shut.

3.

Initial suction pressure of 0.8-1.4 kg/cm2 is optimum for start-up. However, in case, the pressure is higher (1.8-1.9 kg/cm2), propane need not be vented: The count interval between opening of suction RBV and kick starting the compressor may be accordingly reduced.

4.Downcount for compressor is started from the field. On count 5, suction RBV is opened. On count 0, the compressor is started.

5.

Current shoots up to 900A+, remains there for about 8-10 sec (never more than 22sec, as the compressor trips by then), and then comes down to 300A. Immediately, start opening FC328 and PC318 in steps of 5%, to bring up the current, and stabilize it at around 470-550A.

6.

As soon as current rises back to about 480-500A, put PC318 and FC328 on Auto mode. Set point (SP) should be given around the current process value (PV) of each of them (usually 0.6-0.9 for PC318 and 57,000 – 60,000 kg/hr for FC328). The SP may be varied depending upon the trend of the current.

7.Provide propane by gradually opening PCs of D302, D304, D305, D317 and D311, always keeping a watch on the suction pressure, PC318 opening and compressor current.

8.

Simultaneously, take control on the suction temperature by TC318. It may be required to be opened fast initially (keeping a close watch on the current), if the temperature is 25-30*C. Once the temperature starts reducing, put the TC318 on Auto mode, with a SP near its current PV (so that it does not open/close in a jerk). By this time, the discharge temperature starts rising (155-160*C). Gradually reduce the SP of TC318 (in steps of 2-3*C) and bring it down to 7-12*C. Discharge temperature must be made stable at about 165*C. In case, discharge temperature is rising, reduce recycle by reducing the FC328 SP and providing some more propane from the drums.

C-302 propane compressor start-up checks.

S/N Activity

1.

Lube Oil Circuit: Check the lube oil circuit and ensure that both the strainers are clean. Ensure sufficient level in reservoirs and L.O. overhead tank. Check LO sample and confirm that it is crackling and explosivity free. Backflush LO coolers and ensure adequate water flow through them by temporarily opening the drain to mat.

2Start LO circulation and set its pressure at 10.0 kg/cm2. Check working of the turbine LO pump and the auto cut

in system. Keep the turbine pump idling at about 400 rpm.

3Stroke check functioning of PCV-318, FCV-328 and TICV-318. Check operation of suction and discharge RBV-304

and RBV 306.

4Drain compressor casing through all the drains. Drain D-306B. DO NOT ATTEMPT STARTUP UNTILL ALL

LIQUID FROM COMPRESSOR CASING AND COMPRESSOR PIPINGS ARE DRAINED.

5 Purge C302 motor with air and confirm nil explosivity.

6Ensure that E-309 ABC & DEF are in line and fully commissioned. Back flush both the banks and ensure cooling

water flow through the exchangers.

7 Check that all the RBVs of D307 are open. (RBV317, RBV318, RBV319, RBV320 and RBV321)

8 Check quench propane line-up starting from D307 O/L.

Just before starting C-302, line up Nitrogen for buffer gas. Maintain 4.0 kg/cm2 pressure at the compressor buffer gas inlet.

Call fire truck as standby.

Just before start up:C-302 propane compressor start-up checks.

S/N Activity

1. Check the seal oil circuit. Set pressure at 3.0 kg/cm2 on the PDIC. Start seal oil.

2 Inform and get OK from TATA/CPP.

3 Keep standbys in other units to take care of power failure/power dip emergency.

4 Open block valves on FICV-328, TICV-318 and quench block valve near P-307s.

Stripping Gas start up C502 start-up for SEU’s in LR

S/N Activity

1. Start lube-oil circulation and confirm that the flow is all right.

2. Start RCW to C-502 lube oil cooler and jacket. Commissioning cooling water to E-501.

3. Drain D-502, D-503 and check all the trips on the compressor. Keep lube oil/seal oil spare strainers clean and ready for immediate use. Vent gas from the suction, if suction pressure is high.

4.

Start seal oil. Keep s/c and d/c PC on Manual mode (preferably keep the d/c PC 50% - 80% open and s/c PC 15%); wait for the “Ready to Start”, and kick start the compressor. As soon as the compressor is started, d/c pressure starts going up; increase the recycle if s/c pressure and d/c temperature are not high (normal operating values are about 1 kg/cm², and 100*C max.). Slowly take control on the PCs and put them on Auto mode.

5. Keep a track of the d/c temperature, which should not shoot to abnormally high values.

6. Let the compressor run on recycle for some time, and ensure healthiness of all its parameters.

7. Slowly bring up furnace COTs to 320-330*C.

8. Start T-202/T-203 extract/raffinate reflux when top temperature reaches 250 deg C.

UNIT:-- JOB DETAILS:- COMMISSIONING OF WET GAS COMPRESSOR

------------

SN Particulars of Checks

1 Checked that all maintenance jobs on Compressor, GearBox & motor are completed. All vibration probes are installed & connected to vibration monitoring system, all temperature gauges are installed.

2 DCS panel officer and the GCU person informed and communicated properly about the Compressor start up.3 Electrical Supervisor and CPP informed about Compressor startup. 4 Checked operations of all CVs checked viz.: RCV-4, RCV-5, Recycle gas CV (14PCV-416), Suct. CV (14FRCV-301)

and operation is satisfactory.5 Checked the flow and pressure instruments, Port C and Port D Pressure and Port C &D differential pressure

instruments etc. The tapings of all interments are commissioned

EQUIPMENT CHECK LIST- WET GAS COMPRESSOR

6 Checked the Lube oil level &quality (Moisture/ contamination free) in the oil reservoir tank. Lube oil sample witnessed by machinist if required or Lube oil centrifuged if recommended by Machinist.

7 Compressor trips, permissive start etc. checked and the report is made.8 Checked both the Lube oil pumps are healthy and available, Auxiliary pump cut in system working.

Nitrogen accumulator Pressure is normal.9 CW to Lube oil cooler is commissioned. Lube oil circulation is established two hours prior to Compressor start up.

Lube oil filters are cleaned/replaced and pressure differential across the filters is normal.10 Removed all isolation blinds as per the blind list. Checked and updated the blind list.11

Checked for free rotation of the Compressor.12 Cr. LPG (GCU) is ready and kept lined out.13 Power supply to Compressor is energized and the tags put during shut down are removed.14 All liquid drained/pumped out to BDD from the Suction, discharge and recycle line.15 Purged the Compressor with Nitrogen and pressure test the casing for no leaks. 16 Depressurize the casing and tight shut all valves. Pulled the vacuum, RCV-4 opened to bring up Compressor Suct.

Pressure slightly positive. Closed the RCV-4 and again pulled the vacuum.Repeated the procedure 2-3 times to ensure that the Compressor is flushed with hydrocarbons.

17 Commissioned Port-D Eductor and checked performance, Eductor outlet line is lined up and line is free of Condensate.

18 Commissioned Port-E, and Port B/C take off BV is opened and Port –C Eductor outlet is lined up.

19 Ensured that the sufficient gas is available for Compressor start up, Commissioned B/H gas if required and lined up other gases.14D-12 (KOD) checked for no liquid, and normal level in FCCU reflux drum (14D-1X)

20 Compressor is started as per normal procedure, watch kept on the Amp, Pressure build up/ sudden load avoided, Opened Discharge to Cr. LPG unit when Disch. Pressure came at around 60 Psig.

21 Compressor operations stabilized, and all Ports commissioned/ adjusted Ports pressure. 22 Flushing oil strainers cleaned. Checked flushing oil is moisture free and started flushing oil to Compressor.23 House keeping carried out at and around the Compressor.

EQUIPMENT CHECK LIST- WET GAS COMPRESSOR

JOB DETAILS:- DECOMMISSIONING OF WET GAS COMPRESSOR

S.N Particulars of Checks

1 DCS panel officer/ GCU person informed and communicated properly about the Compressor shut down.2 Electrical Supervisor/CPP informed about Compressor shut down.3 The load on the compressor reduced gradually and FCCU feed reduced/ stopped accordingly. 4 Flushing oil to Compressor is stopped.5 Compressor is stopped and the Suction/Discharge RCVs are closed from DCS.6 Checked that the Compressor Suct./disc RCVs are closed, if not closed manually.7

Compressor depressurized to BDD, blocked air injection to Port-E.8 Isolated Port C and Port D.9 Closed Suction/Discharge gate valves after depressurizing Compressor to BDD. Checked that the isolation valves are

not passing and Compressor casing not getting pressurized, as a precaution BV on Suct./Disch lines at FCCU B/L blocked.

10 Lube oil to Bearing circulated till the bearing gets cooled, or as advised by machinist and stopped as per Machinist recommendation.

11 Electrical supply to Motor de-energized in Sub Station. Power supply cut off tagged in field and on the breaker panel in Sub-station.

12 Compressor casing is purged with Nitrogen if recommended.13 Isolation blinds are installed as per the blind list, if compressor shut down is for a longer duration or if compressor is

to be handed over for Maintenance work. Blind list checked and updated.14 Lube oil is checked for any contamination,15 If compressor is tripped or forcefully stopped, Ensured that the RCVs on Suction and Discharge are closed

immediately, Compressor depressurizing to BDD started, flushing oil stopped, and Ports isolated to avoid pressurizing of casing with hydrocarbon gas and to avoid contamination of Lube Oil. Then Followed the steps No.8 on wards as mentioned above.

PROCEDURE FOR STARTING C-9 COMPRESSOR

1) Before starting the compressor check the air side line-up

2) Check the air side OF after cooler line up.

3) Check cooling water line up for intercooler and after cooler

4) Check instrument air supply for panel and all control valves.

5) If everything is 'OK' press "START" on digital panel.

6) After this oil pump will start check oil pressure. (about5.0 )

7) Weight till 'LS & HS' vibration indication appears on digital panel.

8) Press "START" push button (Black colour)

9) High Oil pressure alarm will appear reset it.

10) Compressor will come on load.

11) Check all the parameters on digital panel

FOR STOPPING THE COMPRESSOR

1) Press "STOP" button.

2) Press "1" to confirm stop on digital panel.

3) After stopping the compressor auxi.oil pump will start.

4) Oil Pump will stop automatically after 10 minutes.

5) Cooling water to intercoolers should be kept in line for about 1 hour.

Basic Design

“Exchangers”

Index

Sr. No. Topic Page No.1. What is Heater 502. Heat Exchangers 503. Heat Exchanger designation 544. Heat Exchanger Parts 575. Heat Exchanger- Fluid velocity 586. Basic Steps 60

commissioning of Exchangers De-commissioning of Exchangers 60

7. Equipment Checklist Commissioning of crude exchangers 61 De- Commissioning & handing over of air fin cooler 63 Procedure for handing over APS OHD condensers to carry out

maintenance job64

De-Commissioning & handing over of exchangers( other than crude ) 67 Checking of cooler when in line 69 Routine checks on – Exchangers 70 Cooling water line commissioning 71

8. How the Reboiler works 739. Once through thermosyphon Reboiler 7410. Kettle Reboiler 7511. Trouble shoot in operating – Exchanger, Coolers, & CT 78

What is heater? Heater is device to transfer heat from one fluid to another without direct contact.

Heat exchangers (unfired) is a device in which two fluids flow against the opposite sides of a solid boundary wall which separates them while permitting heat to pass from the hot to the cold fluid

Types of shell and tube heat exchangers.1. Double pipe heat exchangers (DPHE)2. -preferred when area is <150 sq.feet.3. -high pressure service.4. -True counter current flow. Fluids are incompatible –less leaky. 5. -accommodates large temp. differentials

Heat exchanger names. Preheat Train Exchanger Cooler

Condenser Reboiler Inter Cooler After Cooler Waste Heat Steam Generator BFW Heater Fin Fan Air Cooler

TEMA classifications• Class “R” – Refinery and petrochemical services. • Class “B” – Chemical process services. - Less severe services than “R”.• Class “C” – Moderate and general process applications.

Types of shell and tube heat exchangers. Fixed tube sheet –AEM,BEM

o Used when hot and cold sides have low temperature differential (<100 degC).o Lesser gasket joints-less leaks.o Bundle cannot be removed for cleaning. Needs chemical cleaning.

-Low costo Fixed tube sheet with expansion bellow.

Types of shell and tube heat exchangers. Floating head heat exchangers

o AES, BES most common.o Allows for thermal expansion

-Tube bundle can be removed for cleaning.-Expensive

o More number of joints-more leaks. Fluid Routings

Following are preferred in the tube.• High pressure fluids • Corrosive fluids

• Fouling fluids • Slurries or fluids with significant solid loading

Viscous or low flow rates fluids preferred on the shell side.Overall heat transfer coefficient.

• Coefficient meaning heat transferred per unit time per unit area per deg C of temperature differential.Factors governing the overall heat transfer coefficient.

• Nature of fluids.• Nature of material of construction.• Heat exchanger geometry.• Enhancements like fins or other extended surfaces.• Tube side velocity.• Shell side velocity, Operating parameters outside the control of the HEx designer

Heat Exchangers

Heat Exchangers

FurnaceDistillation Visbreaking Cracking etc.Coolers

Steam Generators

Compressor, Turbines

Coolers

Crude Oil

Product s

Water

Lube Oil Water

Lube Oil

Heat Exchanger Designation

Channel & Removable Cover

Bonnet (Integral Cover)

Channel integral with Tube Sheet and removable cover

A

B

C

E

F

G

K

One Pass Shell

Two Pass shell with Longitudinal Baffle

Split Flow

Kettle Type Reboiler

S

L

M

U

U-Tube Bundle

Floating Head Backing Device

Fixed Tube Sheet with A Stationary Head

Fixed Tube Sheet with B Stationary Head

.Tube side considerations

• Higher tube velocity is preferred.• More number of tube passes improves the transfer rates. 2, 4, 6 passes are normal for tube side.

• high velocity will retard the undesired effects like fouling and will improve heat transfer rates which results in lower area requirement.

Pressure drops• Normal design values 0.01 to 1 kg/cm2g. P Varies with (Velocity)^2.

Doubling the velocity will quadruple the pressure drop.Increases with number of passes.Critical in vacuum services.

Fouling• Macro fouling-Macro fouling is caused by coarse matter of either biological or inorganic origin, for example industrially produced refuse.

The economic importance of fouling, Losses due to fouling of heat exchangers in industrialized nations are estimated to be about 0.25% of their GDP, India’s GDP is $738 billion , Thus the estimated monetary losses due to fouling in heat exchangers is 738 crores/A

Fouling factors• Fouling adds thermal resistance to heat transfer.

Fouling factors are specified based on experience.Inclusion in exchanger design will lead to over design.

• Are specified to increase mean time between exchanger cleaning.

Co-current v/s countercurrent• Countercurrent is preferred.• Gives greater average driving force for Heat transfer.

It’s possible to have outlet temperature of cold side fluid to be greater than the outlet temperature of hot fluid.• Smaller area requirement for the same duty.

Actual flow pattern in STHE is mix of two.

Heat Exchanger – Heat Transfer DesignQ =UAtTmQ - Total Heat to be transferred - BTU / HrU - Overall Heat Transfer Coefficient- BTU/Hr. Sq.Ft.oF (Outside fluid, Inside fluid, Tube Resistance, Fouling etc) At - Heat Transfer Area (Tube surface area between tube sheets) Sq.FtTm - Mean Temperature Difference oFFind - At - Total surface Area. Knowing Tube size - Number of tube required From that Shell size can be determined

Heat Exchanger Parts

Channel CoverChannel Cover

Channel Fixed Tube Sheet Floating Tube Sheet

Floating Head Cover Shell Cover

Shell

Baffle

Heat exchangers – Fluid Velocity

Velocity is directly proportional to heat transfer coeff. but erosion and material limits keep the velocity low.

VELOCITY Min / Max

• Tube side for process liquids - 3 / 6 ft/sec

• Tube side for cooling water - 5 / 6 ft/sec

• Shell side liquid - 2 / 5 ft/sec

• Vapour - 20 / 250 ft/sec

Typical pressure drops:

Tube side - 5 – 8 psi Shell side - 3 - 5 psi

Passivation for Stainless Steel (SS) Heat Exchanger During a shutdown, in the presence of air and liquid water, often dew point water, the sulfides convert to polythionic acid

which causes intergranular Stress Corrosion Cracking of Austenitic steels. Applicable to Austenitic Stainless Steel only 300 Series (SS 304, SS310, SS316, SS321, SS347) To Avoid Stress Corrosion Cracking Passivation before Opening Soaked with a solution of Sodium Carbonate (2%) and Sodium Nitrate (0.5%) for about 8 hours Testing with DM Water with Chloride Content less than 25 ppm

Significance of Heat Exchanger Testing

1. Shell Test (Ring Test): will reveal Tube Leak, Roll Leak (Tube & Tube Sheet) Gasket Leak (Channel-Stationery Tube Sheet & Shell-Stationery Tube sheet) 2 Tube Test will reveal: Gasket Leak (Floating Head & Channel Cover)

- Back Shell Test: Gasket Leak (Shell Cover)- 30 minutes, 1.5 / 1.25 times Design Pressure H2O / Air

Trouble shooting: Decline in heat transfer efficiency : will indicate Both sides due to scales, coke, salt deposits etc

Suggested on line actions:

Use of anti-foulants,

water injection,

back flushing cutter stock dilution, maintaining water quality.

Damages & excessive clearance in the baffles.High pressure drop, internal Leak - causing contamination between shell and tube fluids. Floating Head

gasket failure - due to thermal shock during start-up & shutdowns Tube failure - Due to fatigue, ageing & corrosion, Gasket leaks - External

Basic Steps: for De commissioning of exchangers.

1. Bypass hot side slowly to avoid thermal shocks and process upsets

2. Bypass cold side

3. Isolate exchanger valves, both shell & tube sides

4. Depressurize and drain

5. Isolate by blinds both sides

6. Purge with light oil or steam, Wash with solvent/chemical if Necessary and then wash with water or steam-out

Basic Steps in Heat Exchanger commissioning

1. Purge with steam

2. Pull blinds

3. Pressure test nozzle gaskets & exchanger gaskets with steam, oil as per instruction

4. Fill-up and displace air/nitrogen

5. Commission cold side

6. Commission hot side slowly

EQUIPMENT CHECK LIST- CRUDE EXCHANGERCOMMISSIONING OF CRUDE EXCHANGER

S.No Particulars of Checks Done

1 Preliminary Checks:Once the exchanger is back after M & R, certified by MI – proceed for physical inspection of exchanger with respect to Evenly tightening of bolts (no short bolts), installation of bull plugs caps on all bleeders & vents, Thermowell provision, Insulations & Pressure gauge provisions etc.

2 Preliminary Checks -check & confirm provision of Rigid steam connection with check valve on shell inlet & drains have been extended to BDD. Tube (Crude) side to BDD blind removal & Despade Treated water/Steam lines. Provide PG on both the side. Provide igid connection of rigid light oil connection with check valve. Outlet / inlet overflow connection on shell inlet provided( if applicable)

3 Inform DCS officer with full details of commissioning activity. 4 Steam out both side of exchanger till air purging is complete 5 Pinch down the drains/vents, raise steam pressure and check all flanges & other nozzles for leaks 6 Stop Shell side steaming and close the drain. 7 Stop Tube side steaming & close drain. 8 Inform concerned O M & S / Opns personnel about commissioning activities and keep a close watch on the BDD level9 Fill up Tube side with Crude gradually by partly opening crude outlet BV, keep close watch on the crude flow,

Give Sufficient settling time and drain Condensate to BDD & check BDD level gain. 10 Fill up exchanger Shell side with light oil, allow settling and draining Condensates. 11 Open Shell side outlet BV gradually till wide open 12 Open tube (crude) inlet BV gradually till fully open & then pinch down the crude Bypass BV in coordination with DCS. 13 Open shell inlet BV slowly and gradually bring up the temperature, (avoid thermal jerks.) Close the shell side bypass BV

In coordination with DCS14 Watch crude flow, crude safety pressure, and product flow and monitor closely - check all flanges for leak/smoke. 15 Carryout Hot bolting as per requirement once exchanger is full in line & has attained operating temperatures / pressures. 16 Remove all temporary connections steam/drain/light oil etc. install blinds on Tr. Water Connection and BDD lines.

Install bull plugs/caps on all bleeders/vents.

Steps number 11, 12 & 13 are to be done simultaneously.

EQUIPMENT CHECK LIST- AIR FIN COOLER

DECOMMISSIONING & HANDING OVER OF AIR FIN COOLER

SN Particulars of ChecksRemarks status on date & time. .

1 DCS officer is informed and communicated properly

2 Steam / Tr.water / light oil (if viscous oil service) flushing connections and drain connection to BDD / slop R/D (if required) or to sewer are provided.

3 Bypass AFC and close inlet BV, Opening of bypass & closing of inlet to be very gradual.

4 Stop fans after the AFC gets cooled, get the breaker of AFC de-energized & tag the same.5 Watch out the temperature of the product D/S of the trim cooler,

6 Inform concerned person if contents to be drained to BDD or to OM&S if draining to slop R/D or Sewer.

7Flush and displace the content in the tube to IFO / slop R/D. stop flushing and close the out let valve (for IFO/Viscous oil service). For other than the above service, block outlet BV after cooling down the contents.

8 Drain/ depressurize the tubes to BDD/Sewer (as applicable). Ensure that the isolation BVs are holding & tightened properly.

9 Flush the tubes with steam/ hot treated water. Check for effective flushing & all hydrocarbons are removed.

10 Stop flushing oil to tube, drain / depressurize, disconnect flushing oil connections and issue permit for installation of isolation blinds.

11 Get the house keeping done and hand over to maintenance.

PROCEDURE FOR HANDING OVER APS OHD CONDENSERS TO CARRY OUT MAINTENANCE JOB

SRNo

Sequential activity Expected time (hrs)

1 Provide steam connections & extend drain lines to BDD / MAT as shown in sketch below on hydrocarbon side (Shell side). Install a pressure gauge for verification of passing Block Valve, as per the HAZOP approved drawing.

On the run

activity2 Isolate & depressurize CW inlet / outlet block valve to condenser bank. Close HC vapour inlet Block Valves. 2

3 Drain & displace naphtha to D-301 with steam: Isolate CW block valve & drain the condenser -Blind CW side first if CW BVs are passing to the extent blinding is possible. If CW BV is not passing, stop steam once HC O/L line becomes hot. Cross check thru drain point on outlet (Isolate D-301 gas if lined up to C-101 & also keep close check on condensates accumulation in D-5, Routing Condenser out let to close BDD system and close HC outlet BVs.

3

4 Check isolation BVs on HC sides for passing. 15 Once HC BVs are confirmed holding then route HC over flow drain to MAT and starting water filling. Over flow

exchanger shell side with BFW 2” BFW connection – do not allow shell pressure to go beyond 1-2 Kg/cm2.1

6 Stop water filling and allow for blinding HC vapour inlet. 1

7 Drain water from shell to MAT and allow to blind HC out let 3

Notes and cautions: 1. All steam/drain connections with pressure gauge needs to be provided as shown in the sketch.2. While blinding HC inlet at d/s of second isolation BV if first isolation BV is passing, some steam may be kept going at the

spool piece between the two isolation BVs on HC inlet. Steam pressure to be regulated based on the pressure gauge reading provided on the steam line (refer sketch).

3. While displacing naphtha to D-301 with steam, some steam may get travelled to fuel gas drum (D-5) hence constant watch to be kept on the condensates accumulation in D-5 and needs to be drained immediately. D-301 gas if lined up to C-101 suction is to be stopped before displacing naphtha to D-301 with steam.

4. Draining BFW water from condenser after blinding HC vapour inlet need to be done cautiously to avoid possibility of burn injury owing to high temperature.

5. Boiler house to be informed before using BFW for condenser filling.

EQUIPMENT CHECK LIST- OHD CONDENSER

NOTE: 1. BFW water having high temp (appox.110 deg C) may cause burn injury while draining/blinding need to be done very

cautiously and safely. (Providing cold BFW line to be proposed).2. Some steam may get travelled to fuel gas drum D-5 and may get condensed. D-5 level to be watched & liquid to be

knocked off as & when accumulation is found.

11-E-23 ( Btm )

11-E-23 ( Top )

C/W Outlet

Drain to MAT

C/W inlet D-301 drum

2” BFW line

Steam

Steam

11-T-1 O/H Line

BDD

10”

16”

10”

11-E-23 to BDD

¾”

EQUIPMENT CHECK LIST- EXCHANGERS JOB DETAILS: - DECOMMISSIONING & HANDING OVER OF EXCHANGER (Other than Crude )

SN Particulars of Checks Done

1

Check that the following things are done Rigid steam connection with check valve on shell side at higher elevation provided Rigid drain connection to BDD/close sewer on shell side at lower elevation point is provided. Rigid steam connection with check valve on tube side at higher elevation point is provided. Rigid drain connection to BDD/close sewer on tube side at lower elevation point is provided. PGs of suitable range available on both the side

Rigid connection of light oil flushing with check valve and drains extended up to close sewer is provided (if applicable)

2 DCS officer is informed and communicated properly3 The spare or Stand by Exchanger is commissioned as per normal Procedure (if applicable).

4

a) Open the by pass on hot side( shell side) firstb) Open the bypass on tube sidec) Close the isolation valves hot side first followed by cold sided) Check for Pressure/ flow fluctuations

5 Check the ullage in BDD and concerned Supervisor informed6 Cool down the contends to safe temperature7 Drain depressurize the contents to BDD/ close sewer (as applicable)8 Isolation BVs are holding and tightened properly9 Flush the shell side with light oil (if applicable or viscous fluid)10 Steam out both sides of the Exchanger keeping drains on other side open11 Stop steaming once hydrocarbon free and install isolation blinds on both sides.12 Steam out both sides of exchanger properly keeping both sides drains and vents open, and check that exchanger is hydrocarbon free

13 Stop steaming and remove/disconnect steam/BDD/ light oilConnections & hand over to maintenance. Get the house keeping done.

EQUIPMENT CHECK LIST- COOLER JOB DETAILS: - Checking of coolers when in line.

Routine checks on -

EXCHANGER

SN Particulars of Checks Done

1. Check whether the cooler has water supply from C/T or has once thru’ water

2. Check the water outlet temperature of the cooler & ensure that it does not exceed 50 Deg C By the local temperature gauge provided.

3. Check the temperature of the shell side stream by the TT provided ( Reading available in DCS )The temperature should be below it’s Flash point.

4. No leaks at tube head gasket, Channel cover plate gasket, Shell side & channel head sidegaskets

5. Feel the temperature difference between the water inlet & water outlet temperature so as to ensure the proper cooling.

6. All the drains are plugged on shell & tube side.

7. If TRCV ( Three way valve ) is attached to a cooler then check the physical opening of the same & Validate it with DCS opening.

8. This checks are to be done for condensers also, Ensure that number of condensers provided areTo be loaded equally.

9. The TSV provided on cooling water outlet is not passing10. If Water outlet temperature is high then take up cooler for back flushing.

11. If water inlet /outlet temperature does not have expected difference then channel cover Gasket to be checked for damage ( short circuits water inlet to outlet line, )

SN Particulars of Checks Done

1 Most exchanger have been provided with inlet/outlet/bypass block valves on shell & tube sideCheck & confirm shell & tube side inlet /outlet block valves are wide open. Bypass block valves are closed.

2 All the vents & drains on shell & tube side are closed, bull plugged3 No leaks/smoke are seen around the channel cover gasket, channel/ tub head side gasket,

shell side gasket, Channel had side gasket.4 Check Insulation for oil marks / soaking.5 Note the temperatures of shell inlet/outlet as well tube inlet/out let. validate with DCS readings6 The blow down connections are closed & blinded, 7 The rigid BFW, steam, flushing oil connections provided are isolated & blinded.8 No visible leaks around the thermo wells.9 Checks on the color of products to check the exchanger for internal leak. 10 Check earthings, 11 Confirm product routings upto the rundown manifold for correctness. 12 Fire proofing if any to be checked for cracks & If any promptly report.

COOLING WATER LINES COMMISSIONING

Salt cooling water is widely used in our refinery for cooling purposes in our units. Since salt cooling water contain NaCl2, silt, which are highly corrosive & line may see high rate of internal corrosion & erosions due to solid contaminants. In order to prevent both, erosion, corrosion of lines, the CW headers are provided with cement lining to prevent direct contact with CS pipe internals. Thus the cement lining aids in improving life of cooling water headers.

Most critical step involved in commissioning of SCW is AIR displacement with water. If header is commissioned with air, the line will see air hammering due to trapped vapors Hammering will severely damage the cement lining & thus reduce life of the header. Impact of hammering will lead to heavy vibration of header & there by result in damaging the weld joints. Hence all care to be taken to work out a detailed plan before the header commissioning activity is undertaken.

SR. JOB DESCRIPTION

1 Check & confirm completion of Maintenance jobs on the pipeline & get clearance for commissioning from Proj / Maint / MI groups. Carryout proper housekeeping, allow despading the line,

2 Inform DCS Supervisor and concerned department about commissioning activity.

3 a) First & foremost job is Air removal: Provide SCW connection for filling the line & open highest point vent to atmosphere with extended drains connected to drain.

b) Start filling the header slowly & allow air release through the elevated vent. (Highest point in the circuit to be fixed as the place for release of trapped air in the header.)

c) Block off venting once continuous/steady flow of water is established from the vent indicating all air is removed.

d) Allow the line to pressurize up to supply header pressure. Check the circuit for leaks. If no leak, make a final check of air release by opening the vent. If no air,

e) Open the isolation BVs gradually; observe the flow and CW pressure. (As far as possible line to be filled up by opening CW return header BV.)

f) If the line to be commissioned is for the individual cooler or condenser lateral, open the drain/vents at the other end and slowly fill up the line. Ensure the line is filled up completely. Close the drains/vents and open the C W isolation BVs observe the CW flow and pressure. Fill the line up by opening CW return header BV first.

All refineries use reboilers to generate steam by heating boiler feed water by hot products, as well to re-boil the tower bottoms contents especially in gas plants. The typical reboilers used are of kettle & Thermosyphon type and the functioning of the same is as illustrated below:

Field checks on reboilers are as under:

In Kettle type reboiler check for the leaks at the gaskets. Ensure the steam traps on steam condensate outlet are functioning without bypass open. No hammering of the condensate line (due to malfunction of the steam traps ). The vapour return temperature of the reboiler and bottom temperature of the liquid from the tower should be same. The gauge glass to be very clear showing the liquid level. All the inlet, outlet block valves on shell and tube sides are wide open. The liquid level in the gauge glass to be ensured by draining the gauge glass periodically. The level indication revealed by gauge glass and by the instrument should be reconciled. In case of reboilers involved in steam generation continuous blow down of the water to be ensured. Overfilling of reboilers involved in steam generation may lead to serious consequence due to water intrainment along

with steam.

Trouble shooting -exchangers, coolers & CT operation.

1. Exchangers in Refineries are used for handling various types of products like high viscosity, high pour material. In case of process upset or interruptions, the exchangers handling high pour material will require extensive preparation before the temperature drop below the pour point so as to ensure smooth restart. Usually such exchangers would have facility to displace the heavy material with light oil or steam as permissible. The field operator must ensure 100% displacement of high pour material from the unit equipment & the connected lines.

2. Exchanger internal leak is a possibility & this required to be kept in check periodically. Internal leaks will lead to quality problems, carryover of oil to cooling tower, actuation of HC alarms in cooling tower due to internal leak. When such leaks occur, it is a challenge to accurately identify & take corrective steps for stopping the abnormality. The following guidelines will provide simple method for identification of internal leaks in exchangers, they are as given below:

Oil in cooling tower basin: check color, Refractive Index, smell & correlate the findings with the refinery products so as to enable narrow down the search area.

HC detector actuation in CT: Gas cooler internal leaks can lead to HC alarm actuation. Check the source unit through CT returns where HC is present & correlate with connected unit / equipment.

Coolers in the units get fouled up more often during the monsoon & very low tide seasons. Since over 95% of our CW requirements are met through cooling tower system, it will be very essential to carryout blow down of cooling tower basin twice in a day. Also distributor nozzles at the top of cooling tower to be cleaned physically once a week. Post monsoon cooling tower de-silting must be undertaken so as to ensure trouble free pump operations.

Once a week CT fan trip system to be actuated & checked for healthiness of trip system, however fan vibration must be checked in each shift.

Never use fire water for cooling tower make up without seeking approval from concerned CPP officers, shift manager & the F & S safety officers.

Basics of

“Fired heaters”

Index

Sr. No. Topic Page No.

1. How Fire Heaters Works 82

Classification of Heaters 82

Combustion 85

Drought and Combustion Air 87

Burners 89

Fuel Systems 92

Heater tubes 94

Measurements & control 96

2. Trouble shooting 99

3. Typical Fired Heaters 103

4. Normal checks to be done on balanced draft heater when on stream 105

5. Checks- 3 days before the scheduled start up of the furnace after repairs 106

6. Checks- 8 hrs before the scheduled start 107

7. Checks- 0 hrs of scheduled start-up 108

HOW FIRED HEATER WORKS

1.1 Description:The furnace is a piece of equipment in which heat is transferred to the process fluid. The process fluid passes through the tubes

and the heat is provided by the controlled combustion of the fuel (OIL/GAS). The heater consists of the metal structure, which is

internally lined with refractory material. The refractory protects external metal work, reduces heat losses and reflects radiant

heat back on to the tubes. The air required for the combustion of the fuel is provided by the fans or by the natural draught of

the furnace. The atomized liquid fuel or gaseous fuel is introduced into the heater at the burners where it is mixed with

combustion air and ignited. The process fluid to be heated normally enters the heater at the top of the convection section and

leaves from the radiant section. The tubes are arranged along the wall, roof or hearth of the fire box dependent on the design

configuration. The process fluid receives direct radiant heat from the flame and the reflected heat from the refractory walls.

Tubes are also arranged in the duct between the firebox and the stack and receive convective heat from the hot flue gases going

over them. This is known as the convection section of the furnace.

Depending upon the size and the heat duty, heater will vary in design (type of furnace) and the material of construction.

1.2 Classification of Heaters:

Based upon the type of metal structure, the heaters are classified as:

1.2.1 Vertical Cylindrical:

In this type of heaters, the tube stand or hangs vertically in a circle in the radiant section around the floor mounted burners.

The firing is parallel to the radiant section of the tubes. FCCU feed heater 14F – 01X and Asphalt heater 15F – 01 in FR are of

this type.

1.2.2 Horizontal Cabin:

In this type of heaters, the tube extends horizontally on the sidewalls and the sloping roof of the cabin in the radiant section.

Burners are floor mounted in a row down the centre of the cabin and are fixed vertically. FR/FRE crude and vacuum heaters

are of this type. Based upon the method of creating draught for supply of combustion air, the heaters are classified nace. the s:

1.2.3 Natural Draught:

In the natural draught heaters, the draught is obtained by the stack height. Taller the stack, greater the available draught. The

draught is controlled by operating stack damper. Asphalt heater 15F – 01 and FRE Vacuum heater 32F – 01 are of this type.

1.2.4 Induced Draught:

In the induced draught heaters, the ID fan is used for maintaining the draught as the stack gives insufficient draught. The IDF

is located in the ducting between the heater and the stack and sucks the flue gases out of the heater.

1.2.5 Forced Draught:

In the forced draught heaters, the forced draught fan (FDF) is used to supply combustion air to the burners for better air/fuel

mixing. In this case, there is positive pressure in the air supply duct. The CO boiler in FCCU is of this type.

1.2.6 Balanced Draught:

In the balanced draught heater, both the FDF and IDF are used. The flue gases leaving the convection section heats the

incoming air in the Air Pre-heater (APH). Flue gases thus gets cooled (above Sulfur dew point) before discharging to the

atmosphere through stack. CDU, VDU and FCCU heaters in FR and CDU heater in FRE are of this type.

Draft:

Draft is negative air pressure generated by the buoyancy of hot gases inside the furnace. The pressure inside the furnace is

negative because the hot gases are less dense than the outside air. These hot gases weigh less than the cooler air so they are

buoyant inside the furnace. This buoyancy causes the hot gases to rise upward out the stack, creating a slight vacuum inside the

furnace. The vacuum causes the outside air to flow into the air registers. The pressure in the atmosphere is 14.7 pounds per

square inch ( psi) . a negative pressure is any pressure below 14.7 psi. the pressure inside the furnace is maintained just slightly

below 14.7 PSI. this is called a negative pressure. The difference between the outside pressure and this negative pressure is what

creates the draft. Draft is usually measured in three places: at the firebox floor, below the convection section and below stack

damper. The most important draft reading is below the convection section because the negative pressure is smallest here. The

small negative pressure is due to the tubes in the convection section which obstruct the flow of the upward moving gases. This

resistance to flow can cause the pressure in the convection section to shift from slightly negative to slightly positive. When the

pressure shift positive, there is loss of draft. With no draft, heat build up just under the furnace arch and roof which can

damage the structure of the furnace. A loss of draft also means that no air is pulled into the furnace so the burners will

eventually go out. The furnace draft is usually controlled by positioning a damper in the stack. Opening the damper allows more

flue gas to flow out the stack which in turn increases the draft throughout the entire furnace. The increase in draft is measured

as an increase in negative pressure. When the damper is closed, the draft decreases. This is measure as a decrease in negative

pressure. It’s important to maintain the correct furnace draft. Too little draft can damage the metal structure and snuff out the

burners. Too much draft can pull excessive amounts of air into the furnace which wastes fuel.

Draft readings:

Draft readings are a comparison of two pressure taken at the same elevation and traditionally quoted in inches of water gauge.

To make sense of a set of draft readings for the furnace, you must first normalize the data.

In fig. below we see a simple natural-draft heater with no convective section tubes. The laws of hydraulics tell us that fluids flow

from regions of high pressure to region of lower pressure, and yet the draft readings in fig. seem to contradict this principle.

Notice that the draft reading are made at different elevations. Each measurement is in reality a comparison between the

densities of the gas both inside and outside the furnace at a given elevation. The temperature difference is the main reason for

difference in the density inside and outside the furnace. The molecular weights of the furnace gases and of air are approximately

the same. To make sense of the draft measurements so that we can use them to evaluate furnace drop, proceed as follows:

1. make a datum line across the top of the stack as shown in fig.

2. for each draft reading add on the pressure exerted by the appropriate static head of air.

Given: 150 ft of air = 2.22 in H2O ( or inches of water gauge ) in our example which is for 60 deg F ambient air at sea level. the

standard instrument which is used to take draft reading is the magnetic delta-pressure gauge.

1.3 Combustion:

Combustion (Burning) is a chemical combination of fuels element mainly Carbon, Hydrogen and Sulfur with Oxygen. The

chemical reactions involved are accompanied by the release of heat (i.e. the reactions are exothermic). The basic chemical

reactions are:

C + O2 CO2 + 32,840 KJ/Kg of Carbon

2C + O2 2 CI + 9,290 KJ/Kg of Carbon

2H2 + O2 2H2O + 1,19,440 KJ/Kg Hydrogen

S + O2 SO2 + 9,290 KJ/Kg of Sulfur

(1 KJ/Kg = 0.429 BTU/Lb.)

Oxygen required for combustion is supplied as a constituent of air, which is basically 21 vol.% Oxygen and 79 vol.% Nitrogen.

1.3.1 Excess Air:

As the perfect mixing of a fuel with the theoretical quantity of air cannot be achieved in a fired heater, it is necessary to supply

excess air (more than the theoretical quantity of air) to obtain complete combustion of the fuel so as to obtain good and clean

firing.

Natural draught burners are usually specified to operate with 20% excess air on fuel gas firing and 25% excess air on fuel oil

firing. Forced draught burners are normally designed to operate at 10% excess air for fuel oil or fuel gas.

Analysis of flue gas oxygen content is used to determine excess air levels. For combustion control purpose, the flue gas sample

probe is best located at the inlet to the convection section. Gas sampling at this location avoids the effect of air leakages into the

convection section. However, on large horizontal tube heaters, there can be a big variation in flue gas oxygen content at the

convection section. Thus the control is often at the convection section exit with an allowance being made in the heater excess air

operation for air in-leakage rates by regular checks/repairs. The excess air is expressed as a percentage of the excess air to the

theoretical quantity of air required i.e.

% Excess of air = (Air supplied – theor.Air)x100

Theoretical air

For every one part of Oxygen supplied, approximately four parts of Nitrogen leaves the heater. Although Nitrogen plays no

part in the chemical reactions, it does absorb a portion of the heat generated. To avoid excessive heat losses, just sufficient

excess air ought to be provided to ensure complete combustion. Care must be exercised in reducing excess air. Incomplete

combustion is not only inefficient in fuel usage but can be dangerous because:

Unburnt fuel could ignite explosively if a sudden increase in combustion air occurs.

Unburnt fuel may ignite in the flue gas ducting if air leakage occur or where additional air is introduced from other flue

gases in a common ducting.

Whilst smoke from the stack of a fired heater indicates incomplete combustion when oil firing, incomplete combustion can take

place without smoke from a stack when gas firing. Because of this, Oxygen analyzers plays important role in heater operation.

These analyzers continuously monitor the heater flue gas and give warning of incorrect air quantity for combustion. Some heat

is recovered from the gases leaving the combustion zone in the convection section and in steam generating/ superheating coils.

The air pre-heaters are used to warm the air with the flue gases, prior to its entry into the furnace. These facilities increase the

heater’s thermal efficiency. The temperature in the stack must, however, be maintained higher than the temperature at which

acid vapor in the flue gas will condense as condensation can lead to acidic corrosion in the ducting and stack.

It is important to ensure that the flame shape and appearance remain satisfactory when airflow is adjusted because of high

oxygen in the flue gas.

1.4 Draught and Combustion Air:

The hot gases in a heater and stack are less dense than the colder air outside. So the pressure inside the heater is less than the

outside atmospheric pressure.

The slight negative pressure or vacuum, which exists within a heater, is called the draught. These small pressure differences are

measured in millimeter of water gauge (mmWC).

Combustion air for the heater burners is drawn or blown into the heater and hot flue gases flow out of the heater due to this

small pressure difference. The flue gases, in passing through the firebox, convection bank and ducting have a resistance due to

friction. Sufficient draught must be provided to overcome this friction to ensure that the pressure inside the heater is always

slightly less than the pressure outside.

1.4.1 Draught Control:

Whatever means of draught generation is used (natural, induced etc.), it is important that the draught in the heater is carefully

controlled at its specified level (usually 2 – 3 mm WG at the radiant section exit). Control is usually achieved by varying the

position of the stack damper. However, changing the heater draught by adjusting the stack damper affects the airflow through

the burners as well as affecting air in leakage rates. Hence burner airflow rate adjustments may have to be made at the same

time as the stack damper is adjusted.

With natural draught burners, the heater draught and the oxygen content in the flue gas is controlled by operating the stack

damper and the burner registers together. With forced draught burners, the variation in heater draught is not so critical with

regard to the combustion airflow. However, it the combustion airflow is adjusted the stack damper will have to be adjusted in

order to maintain the correct heater draught and in case of balanced draught, the ID fan suction damper need to be adjusted.

If the draught in the heater is too high, excessive amounts of cold air will be drawn in. Because the air will be heated, this

requires more fuel to be burnt to maintain process conditions. Conversely, it there is insufficient draught, the top of the firebox

can become pressurized allowing flue gas to leak through the roof of the heater. This situation should be avoided and may be

recognized by a bluish haze around the heater roof in addition to draught gauge readings.

1.4.2 Combustion Air Preheaters:

Residual heat in flue gas after the convection section is used to warm combustion air in the air pre-heater.

Normally a combustion air bypass with a damper is installed around the air pre-heater so that the outlet flue gas temperature

remains high enough to ensure that condensation does not occur. This is important when sulphur – containing fuels are burnt

as condensate formed would be acidic and therefore highly corrosive.

1.4.3 Soot blowers:

Combustion deposits tend to build up on the external surfaces of convection tubes. This reduces heat transfer from flue gases to

the process fluid passing through the tubes. The build-up, if it becomes extensive, can also restrict the passage of flue gas

through the convection section. This would cause a gradual loss of draught in the firebox.

The effect of convection section fouling are likely to be most noticeable on heaters with finned convection tubes and

predominantly fired with fuel oil. Many heaters are fitted with soot blowers to allow the on-stream cleaning of convection

section deposits. These Sootblowers should be used on a daily basis for effective heater performance.

Sootblowers have either fixed or retractable lances mounted on the side wall of the convection section that removes deposits on

tubes using steam jets. Retractable lances are easier to maintain and are more effective in tube cleaning

1.5 Burners:

A wide range of liquid and gaseous fuels is burned in process heaters. Liquid fuels from light distillates to heavy residual oils

such as vis broken residue are used where as gaseous fuels used contain a mixture of component gases ranging from hydrogen to

butane. Most heaters are capable of burning liquid and gaseous fuels at each burner. Usually fuel oil and fuel gas can be fired

on a burner at the same time (combination burner) whilst in some cases, although the burner has the capability to fire both

fuels, only one fuel is fired at any one time. Burner assemblies are therefore designed to create the conditions required for

controlled, efficient and safe combustion of a range of fuel qualities over a range of heat duties.

1.5.1 Burner Assembly Components:

Air register

Combustion air enters a natural draught burner through an air register, which is designed to ensure even distribution of

the air into the burner quarl. Register air louvers are used to regulate the flow of combustion air. Some burner designs

have two sets of louvers to give separate control of the primary and secondary air.

Wind box

Forced draught burners are supplied with combustion air via ducting to the burner Wind box. Airflow is controlled by

varying the position of damper vanes at the inlet to the forced draught fan. An isolating damper is fitted in the inlet of

the Wind box at each individual burner. This damper is used only for isolation and possibly for start-up of that burner

when other burners are in operation.

Refractory quarl

This is mounted in the furnace floor or wall. The internal diameter is sized to produce a pressure drop, which converts

the available draught i.e. static pressure into velocity pressure.

Primary block

On most natural draught burners and some forced draught burners, in order to stabilise the oil flame the oil gun is

positioned in a primary block. 15 to 20% of the combustion air enters through the block, which should be shaped

internally to allow the correct recirculation of partially burnt fuel and air back to the root of the flame.

Oil Atomizer

To enable efficient combustion the oil is broken down into fine droplets using an oil atomiser. The atomiser usually used

for a natural draught burner is what can be called an emulsion type. Oil is sprayed through an internal jet and mixed

with stream, the resulting emulsion is distributed into the combustion air stream through the gun tip, which will have,

between four and eight holes. On forced draught burners, an atomiser which is frequently used is the internal nozzle mix

type (Y-jet atomiser). The atomiser may have anything between 6 and 20 individual jets each arranged with oil entering

at an angle to a jet of stream which atomises the oil. To avoid oil dripping and coking of burner parts, it is important that

the oil gun position and the tip jet included angle is matched carefully with the primary block and quarl. The tip jet

included angle provides an indication of the atomiser spray angle.

Gas guns

Fuel gas is introduced into the heater via one or more tubes fitted with slotted or multi-hole tips through which the gas is

jetted into the combustion air stream. The tips are designed to ensure efficient mixing of the gas with combustion air.

Gas pilot

A gas pilot is fitted to the burner to provide ignition at start-up and provide a re-ignition source during operation. The

type normally used sucks a portion of its combustion air by using the fuel gas pressure. It has an air regulator, which can

be adjusted to give the required flame. The pilot is fitted with a retention tip which has a ring of jets, protected in a low

velocity area, to provide small retention flames.

Igniter port

A guide tube entered into the burner housing or through the pilot burner body designed to ensure that the heat of an

igniter is correctly located for ignition of the pilot burner. The igniter port is closed by a swing plate, valve or screwed

cap when not in use.

Swirler

This is the multi-vaned disc fitted just behind the tip of the oil gun on a forced draught burner. The swirler stabilises the

flame produced by promoting re-circulation of hot gases to the root of the flame, raising the oil above its ignition

temperature.

1.5.2 Natural Draught Burners:

Combustion air is drawn into a natural draught burner due to the negative pressure (draught) created in the heater firebox by

hot gases rising through the heater and stack. The air velocity through the burner is relatively low. Therefore air/fuel mixing is

slow resulting in a longer flame than that produced by a forced draught burner. To compensate for the less efficient mixing of

air and fuel, it is necessary to operate with higher excess air, typically 20 – 25%.

Flame stabilization (ensuring that the fuel / air mixture continues to burn) for oil firing is provided by the primary block. A

portion of the combustion air passes through the block, which is shaped internally to ensure re-circulation of hot combustion

gases to the flame root. Stabilization for gas firing is achieved also by recirculation of hot gases to the flame root by careful

positioning of the gas burner tips in relation to the burner quarl.

1.5.3 Forced Draught Burners:

A fan provides combustion air and the air is evenly distributed through the burner throat by careful design of the Wind box.

The air velocity through the burner is higher than for natural draught burners giving faster and more efficient air/fuel mixing.

This gives a shorter flame and allows operation with less excess air typically 10%. Flame stabilisation for both oil and gas firing

is provided by hot gas re-circulation to the flame root created by the swirler. The high intensity burner is a particular type of

forced draught burner in which the combustion chamber is built into the burner assembly. Fuel and air are mixed in the

combustion chamber in such a way that a vortex is created resulting in efficient combustion at low excess air typically 10%.

Since much of the combustion takes place in the combustion chamber, the visible flame produced in the firebox can be very

short.

1.5.4 Pilot Gas Burners

There are two basic types of pilot burner in common use. The inspirating type which uses a jet of gas to inspirate (suck) air into

the pilot burner tube outside the main burner assembly. The second type has an independent, piped air supply and is often used

on forced draught burners.

1.5.5 Burner Alignment

For flame stability and combustion efficiency, it is essential that the burner components are in the correct position relative to

one another and are concentric about the centreline of the burner assembly.

1.5.6 Ignitors

There are two types of ignitors. One is electric ignitor and the other is LPG flame torch. The electric ignitor can be of low

voltage carbon arc type, the low voltage high-energy spark type and the high voltage high-tension type which produces spark

similar to a car spark plug. These are all suitable for lighting gas pilots. The units can be portable to allow their use on a

number of heaters.

1.6 Fuel Systems

Fired heaters are supplied with fuel gas, fuel oil or both, in addition, fuel gas for pilot burners is supplied in separate system. If

both light distillate fuel and heavy fuel oil can be burnt in the heater, they are supplied through separate systems. In addition to

these “normal” fuels, there may also be waste gases or liquids burnt in the heater.

1.6.1 Pilot Gas System

Pilot gas is supplied to the heater through:

A remote isolating valve located at grade in a safe location

Dual filters to remove any solid materials, which might block pilot burner jets.

Emergency shutoff valve.

A self-operating pressure reducing valve set to control supply pressure.

A local isolating valve at each burner location.

Purge connections are provided immediately downstream of the remote isolating valve to allow purging of the system.

1.6.2 Fuel Gas System

The fuel gas is collected from various process sources in a fuel gas mix drum. Entrained liquids are knocked out in this drum by

a mesh blanket (demister pad) fitted in the upper section of the vessel. The liquid is discharged to a closed drainage system

(BDD). Fuel gas is distributed from the mix drum under pressure control. The control system relieves excess fuel gas to flare. At

each heater, fuel gas passes through:

A remote isolating valve located at grade in a safe location

Dual filters to remove any solid materials that might block burners.

Emergency shutoff valve.

The pressure control valve (PCV) to prevent downstream pressure falling below the stable burning limit of the burner.

A local isolating valve at each burner location. Purge connections are provided immediately downstream of the remote

isolating valve to allow purging of the system at shutdown.

1.6.3 Fuel Oil System

Fuel oil may be single component e.g. vacuum residue, or a blend of components from several sources. Quality may vary

considerably but calorific value per kilogram of fuel will remain relatively constant. The main property affecting efficient

burner operation is the viscosity of the oil at the burner. To ensure good atomization and clean firing, the viscosity at the burner

should be 15 centistokes. Heavier fuel oils are heated, normally by steam, to maintain the required viscosity at the burner. The

oil is usually atomized by steam in a fuel oil atomizer designed for that purpose. The amount of atomising steam required is

dependent upon the atomizer design and the quality of fuel being fired. The entire system is normally insulated and steam

traced to prevent heat loss and solidification of the oil during cold weather. The fuel oil supply to the heaters is pressure

controlled by spilling a return flow of oil to the fuel oil storage tank. At each heater, fuel oil passes through:

A remote isolating valve located at grade in a safe location.

Dual filters to remove any solid materials, which might block burners.

Emergency shutoff valve.

The pressure/Flow control valve (CV) to prevent oil pressure falling below the stable-burning limit of the burner.

A local isolating valve at each burner location.

Purge connections are fitted immediately downstream of the remote isolating valve to allow purging of the supply pipe work and

the burner respectively.

1.7 HEATER TUBES

The material being heated in a heater may flow through the heater in a number of parallel paths, first through the convection

bank of tubes and then through the radiant tubes; each flow path is usually referred to as a heater pass. Radiant passes may be

installed either vertically or horizontally dependent on the design configuration of the heater.

Different methods of ensuring equal flows through the individual passes are used, depending on whether the fluid in the tubes is

gas or liquid or a mixture of these. For all heaters, there is a minimum pass flow below which tube damage can occur due to

overheating. The minimum pass flows for each heater are specified in individual manuals. The individual straight tubes

belonging to one pass are joined together at their ends using plug headers or welded return bends. Plug headers are used where

access to the inside of the tube is required during overhaul and inspection. Where this is not necessary, welded return bends are

used. With plug headers, the headers are attached to the tube either expanding the tube ends into the header opening or by

direct welding. The plug headers are the places where leakage is most likely to occur. They are located in header boxes outside

the combustion chamber to protect them from direct heat and to make them easily accessible. Steam is usually piped to the

header box so that a fire within the box can be snuffed out. Radiant tubes receive direct radiant heat from the burner flames,

hot flue gases, and indirect radiation via-re-radiation and reflection from the heater refractory. Convection tubes absorb heat

mainly from the hot combustion gases passing over them. To increase the efficiency of these tubes, they are often given larger

heat absorbing surfaces by the use of fins or studs. Convection tubes, particularly those with extended surfaces, require regular

external cleaning to maintain efficient heat absorption. This is commonly done by Sootblowers fitted in the convection section.

Heat is transferred from the outside of the heater tubes to the fluid inside by conduction through the metal of the tubes. Heating

the oil molecules to a high temperature can cause ‘cracking’ with the subsequent formation of coke on the inner surface of the

tubes. The coke layer formed is a poor conductor of heat and causes the heater to be fired harder to maintain the process fluid

at the required outlet temperature. Coke formation may be an inevitable feature of the process e.g. thermal crackers and

Vacuum unit heaters but generally, it is an undesirable outcome of poor operation. Coke can be laid down by flame

impingement itself a result of poor firing conditions or it may be due to low flows on the tube side, which allows high metal

temperature to be attained even without excessive firing conditions. In either event, tube rupture is a foreseeable outcome and if

this occurs a tremendous amount of additional fuel is added to the combustion chamber, which will cause flames to spread

outside the heater.

It is extremely important that the flame impingement on the tubes and low flow through them be avoided.

If the tube metal temperature exceed its design limits, the tube appearance can change, tube scarring may occur, the colour of

the tube may be different to the adjacent tubes or, in the extreme, tube bulges can be seen.

In addition to changes in tube appearance, tube can sag, bow or hog due to a number of reasons. A tube will sag under its own

weight if the tube hangers break or if the tube become grossly overheated. Uneven coke lay down in a tube will make one side of

the tube expand more than the other leading to bowing or hogging.

In oil fired heaters deposits can accumulate over a period of time on the radiant tubes. These deposits may glow red whilst the

tube wall metal is relatively cool and dark or what appears to be tube scarring may be seen. The inexperienced operator may

find it difficult to distinguish between a potential hot spot and harmless scale. However, it is the responsibility of the operator

not only to carry out regular inspections of the heater, but also to report any unusual or suspicious circumstances immediately

to his supervisor.

Following initial lay down of coke in a heater tube a vicious circle has begun in which more and more coke is laid down. Heater

operation not only becomes inefficient (due to higher heat losses in the flue gases resulting from the increased heat input), but

also potentially dangerous. The danger lies in the excessively high temperatures that the tubes may reach thus causing rapid

scaling of the metal and/or tube bulging and possible rupture of the tube.

Maximum allowable tube metal temperatures differ according to the process condition and tube material but they can all suffer

damage due to overheating. As a check against overheating, thermocouples are usually installed to monitor the temperature of

the tube skin at various points within the heater but these can only measure the tube metal temperature local to the

thermocouples that may not be where the overheating is occurring.

The maximum skin metal temperatures of individual heaters are specified in heater manuals.

Visual inspection of the tubes will normally indicate hot spots, hot passes and flame impingement.

1.8 MEASUREMENT AND CONTROL

High Draft : High draft at radiant section exit is higher ( > negative Pressure) than the target. Low Draft : Low draft at radiant section exit is low ( < negative Pressure) than the target level. Low or High oxygen- flue gas O2 content at the radiant section exit is lower or higher than the target.

Problem Cause Solution

High Fuel Gas pressure Burners are plugged Clean burners

Variation in pass outlet temp Unequal pass flow ratesUneven firing

Equalize flow in passesEqualise firing in all burners

High pressure drop thru tubes Coke buildupHigh rate of vaporisation

Decoke tubesReduce flow rate

High excess air operation High furnace draftPoor air/fuel mixingAir leakage in furnace

Reduce furnace draftModify burnersPlug air leakage

Problem Cause Solution

High or uneven TST Flame impingementOver firingUnbalanced pass flowCoke buildupBad thermocouple

Modify burnersReduce firingEqualize flowsDecoke tubesReplace Inst

Positive pressure at arch Damper not open enoughFiring rate highConvection section is fouled up

Open damper

Clean convection section

High flue gas temp Convection section fouledFins burnt offAfter burning in convection sectionOver firing

Clean convection sectionReplace convection tubesModify burnersReduce firing

SR No Description Purpose Safe Actions1 Pass flows Maintain uniform flow

through coilsAvoid over heating, coking & tube burn out

2. Coil outlet temperatures

Monitor the pass flows , Monitor the metallurgy,

calculate efficiency, heat duty

Adjust the pass flows and avoid over heating

3 Tube skin temperatures

Guidance to max firing, radiant heat duty

Alarm for over firing. Adjust firing.

4 Flue gas temperature Monitor temperature profile, establish max firing rate,

fouling in convection section

Carry out soot blowing conv. Sec. cleaning.

5 Flue gas draft profile at burner, radiant & conv. O/L and D/S of

stk. damp

Monitor draft at various places Adjust box pressure to avoid flue gas leakage or excess air ingress.

6 Flue gas analysis Maximise the combustion efficiency

Control excess air through combustion air.

TROUBLESHOOTING

Smoky burner flame Faulty atomization . Inadequate supply of Air. Dirty burner tips. Low oil temperature / too cold oil.

Burner flame Sparky Excessive air Too hot oil. Improper Atomisation. Water in fuel.

Flame is Pulsating Too hot fuel.

Too little air Condensate in Atomising steam. Dirty burner tips. Burner flushing valve passing.

Too long Burner Flame Damper too much open.

Increase in the Firebox pressure. Too High Furnace load. Stack damper not open enough. Plugging of convection section

High Fuel oil Consumption. High Excess air. Lower temperature of fuel oil to burners. Faulty Atomisation Deposits on tube surface reducing heat transfer.

Furnace coil Inlet pressure high. Furnace tubes are coked. A Valve on Furnace outlet is throttled

Flame Backfire. Low fuel oil pressure. Burner tips being fouled up. Low furnace draft. Burner tips being too large. Water in Atomising Steam.

High TST Coked tubes.

Flame Impingement on tubes. Faulty TST indication.

High Stack temperature. Scaling takes place on Convection tubes After burning taking place in the stack / convection section. Excess Air. Improper Corbelling

FIREBOX

RADIANT SECTION

FUEL TO BURNERCombustion AIR

BURNER ASSEMBLY

CONVECTIVE SECTION

BRIDGE WALL SECTION

ROOF TUBE

SHOCK tubeTUBE

WALL TUBE

STACK

STACK DAMPER

TYPICAL FIRED HEATER

Shock tubes

Radiant Tubes

stack

Fire Box

Atmosphere

Bottom firebox

Top firebox

After convection

Before Damper

After Damper

Atmosphere

Normal checks to be done on Balanced draft heater when on stream.

Before proceeding to check the heater, the concerned crew must be equipped with PPE. Fuel Gas KOD to be checked for liquid level & if noticed to be displaced to flare. ( Co ordinate with DCS officer ) Coordinate with DCS officer & confirm all the trips are in line. Note down the coil inlet pressure gauge reading, ensure the drains are plugged. Ensure that the emergency coil steam is isolated & the trap on drain line upstream of isolation block valve is functioning. Check the effectiveness of steam tracing lines of fuel oil supply & return lines & the traps in these are functioning

properly. Ensure the steam trap of soot blower steam header is functioning. Check the openings of the control valves in Fuel oil & Fuel gas service & validate with DCS. Note the local pressure

gauge readings of Fuel gas &fuel oil headers. Note the steam & fuel oil differential reading & the opening of the Steam/Fuel oil PDICV.

Feel the FD & ID for temperature of their motor bearings & fan bearings ( Physically touch & count 10 ) Confirm the opening of the suction control vales of FD & ID & validate with DCS, Note down the load of the same

( AMPS ), Ensure the stand by FD is healthy & Lined out. Note down the discharge pressure of the running FD & ID. Ensure the suction & discharge dampers of running FD & ID are wide open & the discharge damper of stand by FD is

shut, Confirm the stand by FD is not rotating in reverse direction ( May happen in case the discharge damper is not fully shut), Feel the vibrations & noise of the same, any abnormality to be appraised to field officer.

Ensure the pressure gauges of individual burner Fuel oil & gas laterals are working. Ensure that no oil dripping is seen at individual burner blocks. Note down the burners which are down for repairs & Confirm that the atomizing steam is kept on (For burner tip

protection.) Check & note the furnace draft gauge reading & fresh air duct pressure. Check the firing pattern in the heater & adjust the same, Furnace goggle is must while checking the flame pattern thru’

the peep holes. Ensure that there is no flame impingement & sooty flames. Ensure that the explosion doors are shut. Feel the temperature of the entire furnace shell & note down the areas where temperature is high (should be between 70

to 90 Dg C.) Inform field supervisor. Check for oil soaked insulation & prepare the list & hand over to maintenance. Check the Feed Flows & Temperatures of feed outlet (Coil outlet) & Flue gas out let temperature Ex-APH ( to be in the

range of 155 to 160 Deg C), any deviations inform the field officer & DCS officer.

Checks– 3 days before the scheduled start up of the furnace after repairs.

Ensure the Readiness of the utilities such as Steam, Instrument air, Fuel oil supply & return headers, Gas headers (Pilot & main Gas).

Igniter availability Blinds status list. Trip checking to be completed & logged. Burners installed after verification of their cleanliness. Steam tracings of fuel oil supply & return headers to be functional with proven steam traps. Availability of rotary equipments & the correct directions. Damper operations of FD/ID & stack with clear position indicators. Availability of local gauges for pressure, temperature. Availability of steam header for atomization of fuel & soot blowing. House keeping around furnace & decks. Availability of communication system. Review the details of furnace refractory dry out procedures & keep required connections ready.

Checks -8 hrs before the scheduled start: Stroke check control valves on FO, FG, atomizing steam, return header PCV. Fuel supply and return headers in ISBL to be filled with LFO, settled and drained off water. Final verification of spade removal. Knock off any liquid from FG KOD. Commission steam header & blowout condensates thoroughly. Flush all burners with steam. Keep PPE’s ready near furnace Inform all concerned supervisors regarding the start up plans. Energize required pumps & reconfirm direction of rotations Follow procedure for Establishing furnace draft, (reconfirm damper operations.) Start FD fan and attempt lighting pilot burners & stabilize the operation.

Follow Instructions / procedures for cold circulations, steaming introduction through coil as per requirement. Get all flow / pressure / temperatures verified.

Checks at 0 hrs before the scheduled start: Take start up clearance from Mechanical, Instruments, electrical. Inform confirmed unit managers, supervisor, Stop all work permits on heater & related upstream, downstream equipment. Inform utilities section for close monitoring of FO/ FG / steam header pressures. Obtain clearance from Off site supervisors regarding product routings, suction line ups. Give final up dates to all field personnel on start up plans. Proceed for lighting main burners and proceed for start up as per normal start-up procedures.