steam trap guide

8/8/2019 Steam Trap Guide

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The Steam and Condensate Loop 11.6.1

Block 11 Steam Trapping Selecting Steam Traps - Canteen Equipment; Oil Transfer / Storage; Hospital Equipment Module 11.6

Module 11.6

Selecting Steam Traps -Canteen Equipment;

Oil Transfer /Storage;

Hospital Equipment

S C - G

C M - 8 4

C M

I s s u e 2

© C

o p y r i g h t 2 0 0 6 S p i r a x - S a r c o L

i m i t e d



The Steam and Condensate Loop11.6.2

Block 11 Steam Trapping Selecting Steam Traps - Canteen Equipment; Oil Transfer /Storage; Hospital Equipment Module 11.6

Selecting Steam Traps

Key:A - Best choice.

B - Acceptable alternative.

1 - With air vent in parallel.2

- At end of unlagged cooling leg. Minimum length 1 m.3 - Use special tracing traps which offer fixed temperature discharge option.4 - If the equipment is temperature controlled, a condensate pump and trap combination may be required.5 - With close to steam temperature capsule.6 - Fitted with anti-air-binding disc.

Application

FT FT-C TD BPT SM No.8 IBrange (float- range (Balanced (Bimetallic) (Liquid range

Steam trap: (float- thermostatic (Thermodynamic) pressure expansion) (Invertedthermostatic) with steam thermostatic) bucket)

release)

Canteen equipment

Boiling pans - tilting B A2, 5

Boiling pans - fixed A B B1 B

Boiling pans - pedestal B A2, 5

Steaming ovens A2, 5

Hot plates B A2, 5

Oil transfer/storage

Bulk oil storage tanks A B1

Line heaters A B1

Outflow heaters A B1

Tracer lines B A B2 (non-critical only) B

Jacketed pipes B1, 6 A5 B1

Hospital equipmentAutoclaves and sterilisers B B A5

Industrial dryers

Hot air dryers A B1 B

Drying coils B1 A B1

Multi-bank pipe dryers A B1 B B1

Drying cylinders B A B1

Multi-cylinder sizing machines B A B1

Laundry equipment

Garment presses B B A6

Ironers and calenders B A B1 B5

Tumbler dryers A BDry cleaning machines A B1





FT FT-C TD BPT SM No.8 IBrange (float- range (Balanced (Bimetallic) (Liquid range

Steam trap: (float- thermostatic (Thermodynamic) pressure expansion) (Invertedthermostatic) with steam thermostatic) bucket)

release)

Presses

Multi-platen presses

(parallel connections)B A6

Multi-platen presses(series connections)

A1, 6

Tyre presses B B1 A B1

Process equipment


Boiling pans - tilting B A

Retorts A

Industrial autoclaves A B1

Digesters A1 B1

Hot tables B B6 A2

Brewing coppers A1 B

Evaporators, calandrias A1 B B1

Vulcanisers A B1 (jacket only) B1

Space heating equipment

Calorifiers A4

Heater batteries A4

Radiant panels and strips A B1 B1 B1

Radiators and

convection cabinetsB A B

Unit heaters and air batteries A4

Overhead pipe coils B A B1

Steam mainsPressure reducing valve station A B5

Horizontal runs B A B

Shutdown drain(frost protection)

B3 B A

Separators A B B

Steam header drainage A B6 B

Terminal ends B A1 B1

Tanks and vatsProcess vats(rising discharge pipe)

B B A B5 B

Process vats

(discharge pipe at base)A B6 B5

Small coil heated tanks

(quick boiling)A B5

Small coil heated tanks(slow boiling) B A





Canteen Equipment

A - Best choice, B - Acceptable alternative, 1 (parallel air vent), 2 (with 1 m cooling leg), 5 ('near-to-steam' capsule).

Ball float- Ball float Thermodynamic BalancedBimetallic

Liquid InvertedApplication thermostatic FT-C pressure expansion bucket

Boiling pans - tilting B A 2, 5


Boiling pans - pedestal B A 2, 5

Steaming ovens A 2, 5

Hotplates B A 2, 5

Canteen boiling pansAlthough similar in construction to process jacketed pans, canteen boiling pans do not normallyhave the same need for rapid heating, consequently the steam pressure is normally lower.Condensate loads will normally be much lower. Whilst air and condensate removal are not socritical, air vents can still be useful in reducing heat-up times.

Tilting boiling pans

Figure 11.6.1 shows a balanced pressure thermostatic trap, draining a slow boiling tilting pan. Abalanced pressure air vent (fitted as shown) will speed up the boil of, for example, 140 litres of soup by about 20 minutes. If faster cooking would be an advantage, an air vent should be fitted.A good alternative to the balanced pressure steam trap is a float trap with steam lock release.

Air vent

Fig. 11.6.1 Slow boiling tilting pan

Pedestal boiling pansThe correct way to drain pedestal boiling pans is to use a balanced pressure thermostatic trap andstrainer. For efficient operation this should be fitted about 1 m away from the outlet at the end of the cooling leg (Figure 11.6.2). There is usually no need to fit an air vent on this type of pan.

Fig. 11.6.2 Pedestal pan

Condensate tovented receiver

Balanced pressuresteam trap







Steaming ovens and hotplatesFigure 11.6.3 shows an ideal layout for draining and air venting steaming ovens. There are threevital features:

o The steam inlet must be drained just before the inlet valve by a balanced pressure thermostatictrap.

o Each compartment outlet must have a similar trap direct on to the outlet, but without a strainer(to let the greasy condensate pass through before the grease cools).

o The traps draining the compartments, and the air vents, should be fitted with near-to-steamelements. The ovens should be blown through with steam after cooking has finished.

Fig. 11.6.3 Direct steaming oven

Steam in

Condensateto waste

Air vent

Air vent

Eachcompartmentseparatelytrapped

Figure 11.6.4 shows a kitchen hotplate fitted with a Fig 5 type strainer, close coupled to a balancedpressure thermostatic steam trap, an ideal combination for this application.

Fig. 11.6.4 Kitchen hotplate








A - Best choice, B - Acceptable alternative,1 (parallel air vent), 2 (with 1 m cooling leg), 5 ('near-to-steam' capsule), 6 (anti-air-binding disc).

Ball float- Ball floatThermodynamic

BalancedBimetallic

Liquid InvertedApplication thermostatic FT-C pressure expansion bucket

Bulk storage tanks A B1

Line heaters A B1

Outflow heaters A B1

Tracer lines B A B2 (non-critical only) B

Jacketed pipes B1, 6 A5 B1

Bulk storage tanksOil and other fluids are stored in tanks that are heated by pipe coils or other forms of heating,either alone, or in combination with outflow heaters, to provide the correct temperature forpumping. Line heaters raise the temperature of fuel oil to that required for burning or for processuse.

There are several ways to heat small to medium sized storage tanks, such as with pipe coils(Figure 11.6.5) spread across the bottom of the tank, or with 'bayonet' or 'field' heaters(Figure 11.6.6). In these situations a large pipe, sealed at both ends, is fixed through the side of the tank. Steam is fed to the remote end by an internal pipe and condensate is removed from thenearest end. However, on larger tanks, one of the more widely used methods is the fitting of anumber of special heaters served from an internal ring main as in Figures 11.6.7 and 11.6.8.With all coil configurations it is essential that each pipe section or each heater is separatelytrapped.

Long coils are susceptible to waterhammer, as they will collect condensate along theirlength. Because of this, it makes sense that coils are designed with a constant fall in the directionof steam flow. The modern float-thermostatic trap is equipped to withstand high levels of

waterhammer, but if the symptoms are extreme, an inverted bucket trap or balanced pressuretrap is a good choice. It may be necessary to lag float-thermostatic traps to protect themagainst damage by freezing. The inverted bucket trap may require a separate air vent to befitted in parallel to remove air from the coil on start-up.

Oil Transfer /Storage

Fig. 11.6.5 Oil storage tank - pipe coil

Steam in

Condensate to drainCondensate to drain





Fig. 11.6.6 Oil tank - bayonet heater

Steam in

Condensate to drain

Oil heater batteriesThese are single or multi-stage heat exchangers and should be treated in a similar manner tooutflow heaters. Each stage should be individually trapped and since they are often fitted indoorswhere the traps are not likely to freeze, float-thermostatic traps are the best choice.

Fig. 11.6.8 Three section oil heater battery

Steam in

Air eliminator drainingto a safe place

Oil in

Condensateto drain

Oil out

Fig. 11.6.7 Large oil tank with multi-heaters

Steam in

Tank

Steam ring mainHeater sections

Condensate out





Tracer linesTracer lines should be arranged to fall in the direction of steam flow and should not exceed25 metres in length for 10 mm tracers or 50 metres for all larger sizes, each length being drainedby a balanced pressure thermostatic tracing trap or a thermodynamic trap. It is preferable to runsingle tracers near the bottom of the product line, and where it is necessary to pass flanges, thisshould be done with a horizontal loop to help maintain a continuous fall towards the trap.

Outflow heatersAn outflow heater is a shell and tube heat exchanger installed in the side of a storage tank, whichheats the oil locally as it is pumped out of the tank. Automatic temperature control is usual andFigure 11.6.9 shows a Spirax Sarco self-acting control with the sensor in the oil outlet, actuating a valve in the steam supply.

The first choice is to use a float-thermostatic trap. If exposed to the elements, it should be

insulated. It is normal for condensate to be wasted due to the risk of contamination by the oil,but if condensate is being returned and lifted up to a return main it is not recommended that it is lifted by its own pressure, as flooding and waterhammer are likely at light loads. A pump/trapinstallation may be used under these conditions.

Fig. 11.6.9 Outflow heater

Oil in

Condensate to drain

Tank

Oilout

HeaterTo condensate system

Steam in

Fig. 11.6.10 Steam tracer line

Condensate to return or to waste

Balanced pressure trap

Oil pipeline

Steam

Float-thermostatic trap





Oil pipe tracing is not normally considered 'critical', and where condensate is discharged towaste, a bimetallic trap or a balanced pressure thermostatic tracing trap (in the constant temperature discharge mode) can be used. This will conserve energy and prevent unsightly flashsteam. However, if critical tracing is considered essential, a thermodynamic or balanced pressuretrap, discharging close to steam saturation, should be used.

A convenient method of supplying steam to large numbers of tracers on process lines, and for

draining condensate from them, is to use distribution and collection manifolds. These are shownin Figure 11.6.11, along with universal steam traps, and pipeline connectors with integral isolationvalves. These allow traps to be changed quickly and without any downtime.

Fig. 11.6.11 Typical tracing application with steam and condensate manifolds

Steam

Steam manifold

Tracer line

Process line

Control system

UTD steam trap withpipeline connector

Condensate to wasteBlowdown to wastevia a diffuser

Condensate manifoldSteam traps

Condensateto return

Jacketed pipesWhen the temperature of the product is critical (because of the danger of solidification, burning or vaporisation) the complete product pipeline is 'traced' with a steam jacket. This application isoften seen in 'sulfur' plants.

Jacketed pipes are generally constructed in not more than 6 m lengths and ideally, each lengthshould be separately trapped using a balanced pressure thermostatic tracing trap, (Figure 11.6.12),or a TD trap.

Fig. 11.6.12 Typical steam jacket with balanced pressure trap

Steam in

Process flow

Condensate to return or to waste

Process pipeline

Steam in

Steam jacket

Condensate out Balanced pressuretracing trap





It is, however, quite practical to join up to 4 lengths together, but it is important to join the jackets both at the top and bottom (Figure 11.6.13) so that the steam and condensate can flowfreely and independently. It is worth noting, since many jacketed pipes are exposed to theelements, that the steel bodies of the thermodynamic and balanced pressure traps are not damaged by freezing.

Fig. 11.6.13 Steam and condensate lines between connecting jackets

Condensate connection

Steam connection





Fig. 11.6.14 Hospital autoclave with filtered steam supply

Autoclave

Condensatefrom separator

Controller

Steam in

Safetyvalve

Filter

Jacketair

vent

Steamtrap

Chamberair vent

Condensatefrom jacket

BPT typesteam traps Filtered steam

to chamber

Condensate from chamber

Condensateto fall to a

vented recieverFloat-thermostatic trap

Hospital Equipment

A - Best choice, B - Acceptable alternative, 5 ('near-to-steam' capsule).

Application Ball float- Ball floatThermodynamic

BalancedBimetallic

Liquid Invertedthermostatic FT-C pressure expansion bucket

Autoclaves

and sterilisers B B A5

Autoclave and sterilisersThe draining and air venting of modern high vacuum sterilisers is very important and themanufacturer normally supplies the necessary trapping equipment with the machine.

Figure 11.6.14 shows an autoclave supplied with plant steam for the jacket, and filtered steamfor the chamber. The steam supplied to the chamber must be dry, so a separator drained by afloat-thermostatic trap should be fitted to the steam line. For the chamber a balanced pressurethermostatic trap with near-to-steam capsule can be used successfully. On large units a float-thermostatic trap may be needed. A strainer to protect the trap is important, as it will catch anyfibrous material or broken glass. If the steam inlet to the jacket is at the bottom or at one end, anair vent at the top or the far end will give better heating. The jacket may be drained with abalanced pressure thermostatic trap-strainer unit.

On new systems, there is an increasing requirement to use all stainless steel pipework andfittings to comply with European and International standards. In many cases, this will require theuse of 316L steam traps.

steam trap guide

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