control valve final

7/29/2019 Control Valve Final

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CONTROL VALVES

Presented By:- Guided By:-Jyoti Ranjan Naik Mr. Rakesh Yadav

Souraj Ranjan Patel (Junior Manager, Instrumentation)

Dhiren Mohapatra

Umasankar Paragniha

Santram Kumhar

Kulamani Barik


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CONTROL VALVE

A CONTROL VALVE IS A FINAL

CONTROL ELEMENT AND A POWER

OPERATED DEVICE WHICHMODIFIES THE FLOW RATE

IN A PROCESS CONTROL SYSTEM.

TO DO THIS THE VALVE MUST:


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Cont.

Contain the fluid without externalLeakage.

Have adequate capacity for the

intended service

Be capable of withstanding the erosive,

corrosive, and temperature influences of

the process

Appropriate end connections to mate

with adjacent pipelines


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ROLE OF A CONTROL VALVE

It is used for

The correct distribution and control of

Flowing fluid or gases

Reduction of Pressure

As a variable orifice

As a throttling or modulating equipment


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CONTROL VALVE PARTS

1. BODY

2. VALVE3. ACTUATOR


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The body is the pressure carrying part and itmeets all their applicable pressure,

temperature and corrosion requirements.

THE BODY PROVIDES

THE PIPING CONNECTING ENDS

FLUID FLOW PASSAGE WAY, AND

SUPPORT THE SEATING SURFACE

THE VALVE CLOSURE MEMBER

BODY


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INLET OUTLET

STEM WITH

PLUG

GLANDPACKING BODY FLANGE

SEAT

BODY- INTERNAL PARTS


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ACTUATOR


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.

ACTUATOR

UTILISES AIR PRESSURE / ELECTRIC POWER

HYDRAULIC PRESSURE

TO ACT ON A DIAPHRAGM / PISTON AND

DEVELOP A FORCE TO MOVE THEACTUATOR STEM


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PNUEMATICALLY OPERATED DIAPHARGM

ACTUATOR

PNUEMATICALLY OPERATED CYLINDER

ACTUATOR

MOTOR OPERATED PISTON ACTUATOR

HYDRAULIC OPERATED PISTON

ACTUATOR

ACTUTATOR

CLASSIFICATION


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DIAPHRAGM

CASINGS

LOCK NUT

STEM CONNECTOR

SPRING ADJUSTER

ACTUATOR STEM

ACTUATOR

SPRING

BONET FLANGE

VENT

SCALE

STUFFING BOX

YOKE

DIAPHRAGM

GLAND STUDS

SPRING SEAT

DIAPHRAGMPLATE

INPUT SIGNAL

INDICATOR

ACTUATOR PARTS


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.

YOKE

A STRUCTURE BY WHICH THE

DIAPHRAGM ASSEMBLY IS SUPPORTEDRIGIDLY ON THE BONNET ASSEMBLY


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TRAVEL SCALE

SPRING

ADJUSTMENT

SPRING BASE

NUT

STEM COUPLING POINTER

ACTUATOR BASE

BONNET BASE

YOKE


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TRIM

The trim of the valve consists of all theparts which will be wetted other than the

body and the bonnet

Trim is the heart of the valve with aprimary function to proportion the valve

orifice in such a manner that a

prescribed relationship exists betweenflow capacity and valve plug lift

The secondary function may be shut off

tightly.


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The trim includes Seat, Plug, Stem, Gland

Follower, Gland Nut, Plug, Guide Bushingsand Cage

Stuffing box components considered as trim

are the packing, follower, Spring, LanternRing, and Packing Retaining Ring.

Secondary trim parts are stem to plug

attachments , seat retaining ring, seat to bodyseals and spacers.

T Of C t l l


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Types Of

Controlvalves

Manual Motorized Hydraulic Pneumatic

PowerCylinderDamper

Single ActingDoubleActing

Valve

Ball, Gate,

Butterfly, etc.ATO/ATC

Types Of Control valves


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Hydraulic operated Valve:-

A fluid or oil is used to operate this valve.

Pneumatic operated Valve:-

Operating fluid is compressed air.

Manual operated Valve:-

Operated by human with the help of lever

Electrically operated valve.

Solenoid operated Valve:-Operated electromagnetically through supply of 0-24 volt

dc.

Motorized operated Valve:-

operated through electrical motors such as servo motor.


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Globe valve:

Disc or plug moved perpendicular to flow and closes ona ring seat

Throttling, general purpose flow control valve

Advantages faster than gate, seat less

Wear and tear, high pressure drop forpressure control.

Disadvantage high pressure drop,require considerable power tooperate (gears and levers), heavy


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Butterfly Valve

Rotating disk on a shaft, in a housing

Low pressure, large diameter lines where leakageis unimportant

Advantages low pressure drop,

small and light weight

Disadvantages high leakage,high actuation forces so limited

to low pressures


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Gate Valve Sliding disk, perpendicular to flow

Applications: Stop valves, (not throttling),high pressure and temp, not for slurries,

viscous fluids Advantages low pressure

drop when fully open,tight seal when closed,free of contamination buildup

Disadvantages vibrationwhen partially open,slow response and large

actuating force


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Gate Valve

B ll V l


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Ball ValveFEATURES

Oldest of all valves, applied for wide range of application.

APPLICATION Pressure control , flow control & shut off application .

Can be used for corrosive fluids

Used for high temp application, LPG application.

ADVANTAGES Low pressure drop

Tight shut off.

Quarter turn application.

Small in size & lighter in weight.

DISADVANTAGES

Cannot be used for throttling application.

Fluid trapped in ball may cause corrosion.


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Ball Valve


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Needle valve

Its having a small part and a threadedneedle shaped plunger

Used in flow metering application

specially when a constant calibrated lowflow rate must be maintained for some

time

Its cannot be used in simple shut offvalve because of slow operation

It has tight leakage proof closing.


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Types of valves used in NECO

AIR TO OPEN

(Normally closed, Forced to open)

AIR TO CLOSE

(Normally open, Forced to Close)

U d t


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Used at. CCM :-

Primary & secondary cooling- Air to close (ATC)

Co jet:-

In O2, Propane gas, cooling water line- ATO

V.D.- Air to open (ATO)

Turbine:_Gland steam, PRDS, hotwell, Desuperheater- ATO

Boiler:-

For oil line ATO

Temperature, Steam pressure control v/v. - ATO


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Components In C.V.

Positioner

Air filter regulator

Current to pressure converter i.e. (I/P)

Air lock Relay

Feedback transmitter

P i i


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Positioner

A positioner is a device put into a valve to ensure

that it is at a correct position of opening as per thecontrol signal.

Works on the principle of force balancing (springforce and valve force).

Positioner senses the valve opening through aposition feedback link connected to valve stemwhich is its input signal.

I/P converter output is its set point input.

Hence positioner is nothing but a pneumaticfeedback controller.


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Air Filter Regulator

Air filter regulator regulates the input pressure of

the air into the desired output.And secondarily filters the moisture, foreign

particles etc in supply air.


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Current to Pressure converter

Instrument used to transmit dc mA input signal to

pneumatic signal. Its works on the process of magnetization.

Its basic components in I/p converter of I.L. is

flapper, nozzles, permanent magnet, coil. Input- 4 20 mA.

Output- 0.2 1 kg/cm^2.


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I/P Converter


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Air Lock Relay

Its a reliable unit for achieving stay put conditionof control valve on air supply failure

It is similar to the non returning valve.

When the supply pressure falls below the set valueit comes into action

The set up value is generally higher than that of theoperational valve.

Its setup value is given by the compressing thespring by spring adjusting screw.


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Feedback transmitter

It works on the principle of potentiometer. It provides the feedback of the valve position and

helps positioner in the error correction.

Its is connected to the stem of the valve andthrough its up and down movement its gives thefeedback.

Potentiometer is a variable resistance measuring

device.,


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Calibration Of Control Valve

Calibration is a comparison betweenmeasurements one of known magnitude orcorrectness and the other is of unknown

correctness. The device with the known or assigned

correctness is called the standard. The seconddevice is the unit under test or testinstrument.


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AFR 1

AFR 2

Air supply at

6 kg/cm^2

Air at a pressure

3.5 kg/cm^2

I to P

ConverterPositioner

0.2 to 1

kg/cm^2

DCS Signal


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AFR 1

AFR 2

Air supply at

6 kg/cm^2

Air at a pressure

3.5 kg/cm^2

Master Cylinder

0.2-1 kg/cm^2


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To calibrate a valve first check the input signalrange if it is 0.2 to 1.0 Kg/cm2 or different.

Calculate the span ( Difference between higherlimit to lower limit=1.0-0.2=.8 )

Now divide it in four equal parts that is 0.2Kg/cm2 this is 25% of the span.

Now check the valve travel like 2 inches, 3

inches or any other value Divide it in fourequal parts 25% of the travel.

.

PROCEDURE


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Apply 25% of the span value+ 0.2= 0.4 Kg/cm2it is 25% of travel and apply full span value and

see you get the complete travel if you finddifference adjust the spring accordingly.

We can also use DCS for calibration by

sending signal i.e. current(4-20 mA) and candetect the % of valve opening.


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Data Required For Calibration

PRESSURE

(kg/cm^2)

CURRENT

(mA)

% OF VALVE

OPENING

0.2 4 0

0.4 8 25

0.6 12 50

0.8 16 75

1 20 100


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Problems in Control valve

Moisture problem in AFR.

Filter chocking

Calibration linearity error.

Valve components failure

Positioners cam wheel rusting & cam

misalignment


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Shutoff valve It is a digital way of valve which works

either for full opening or closing i.e. 0or 100%

Its used for safety purpose and also in

emergency conditions. It is generally operated by solenoid

valve which pneumatically operates

the power cylinder or diaphragmvalves.

In simple shutoff valve generally

needle valve is not used.


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Advantages of Shut off valve

Quicker in operation. Low in cost.

Can be operated with small effort.

More accurately the flow can be controlled. Less chances of human error.

Many valves can be operated simultaneously at a

time. Tight shut off.

Heavy wall can be easily operated.


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Limitation:-

It Can Only Operate Either 0 or 100%

It Cant be used for throttling action


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QUERIES


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QUERIES

If

ANY?

control valve final

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