Different Types of Steam Traps & their Functions

1. DIFFERENT TYPES OF
STREAM TRAPS
Prem Baboo
Sr. Manager (Prod)
National Fertilizers Ltd. India
F.I.E., Institution of Engineers (India)
Technical Advisor & an Expert for
www.ureaknowhow.com

3. STEAM TRAP
The purpose of a steam trap is not as the
name may indicate to trap steam, but rather to
trap condensate in a steam line.
The trap should be closed when steam is
present in the line.
It is usually important that the traps perform
closing and opening quickly to reduce steam
and condensate losses.

5. There are three types of
steam traps, they are:
1. Ball float & bucket traps are mechanical steam traps.
They operate be response to the difference density between and steam and
condensate
2. Thermostatic steam traps operate by noticing the
temperature difference between condensate and steam.
3. Thermodynamic traps operate by the difference in
thermodynamic energy between steam and condensate.

6. Mechanical steam traps.
Ball Float Trap
Inverted Bucket Float
Open Bucket Float

7. Ball float steam trap

8. Ball Float Steam Trap

9. Open Bucket Float

10. Open Bucket Float

11. Advantages
Discharge condensate continuously as rapidly as
its forms.
High air venting capacity through auxiliary
balanced- pressure air vent. Which is self
adjusting for varying steam pressure.
High thermal efficiency at both light and heavy
loads.
Steam lock release facility available.
Fair resistance to water hammer.
Wide range of orifices to suit in let pressure.

12. Limitations
Can not be used on high degree of
superheat.
Application subjected to freezing must be
protected with insulation and S L R.
Water hammer can damage the float.

13. Typical Applications:
Air unit heater.
Hot water heater.
Heat exchangers
Converters
Reboilers
Jacketed pans

14. Inverted Bucket Float
Main valve
Inverted bucket

15. Inverted Bucket Float

16. Advantages
Fair resistance to water hammer.
Can be made for high pressures.

17. Limitations
Low thermal efficiency under varying
loads and pressures, some steam loss for
operation.
Must maintain water seal to avoid
continuous discharge of steam.
Must be protected from freezing.
Cannot discharge condensate continuously
as it forms.

18. Typical Application.
High pressure indoor steam main drips and
submerged heating coils.

19. Operation

20. Liquid expansion steam trap
Balanced pressure steam trap
Bimetallic steam trap
Thermostatic Steam Traps

21. Liquid expansion steam trap

22. Installation of a liquid
expansion steam trap

23. Advantages
It is able to withstand vibration and
water hammer conditions.
Prevents flooding of heating surface
during cold startup.
Liquid expansion traps can be adjusted
to discharge at low temperatures,
giving an excellent 'cold drain' facility.

24. Limitations
Not pressure balance.
Since the liquid expansion trap discharges
condensate at a temperature of 100°C or
below, it should never be used on
applications which demand immediate
removal of condensate from the steam
space.
The liquid expansion trap is not
normally a trapping solution on its own,
as it usually requires another steam
trap to operate in parallel.

25. Balanced pressure steam trap with
replaceable capsule

26. Balanced pressure capsule arrangement

27. Operation of balanced
pressure steam trap capsule

29. Advantages
High air venting capacity for fast startups.
Self adjusting to all pressures within its range.
Sealed capsule is free from maintenance.
Doubles as an air vents and vacuum breaker.
The valve is fully open on start-up, allowing air and
other non-condensable gases to be discharged
freely and giving maximum condensate removal
when the load is greatest.
Trap maintenance is simple. The capsule and valve
seat are easily removed, and replacements can be
fitted in a few minutes without removing the trap
from the line.

30. Limitations
In common with all other thermostatic traps,
the balanced pressure type does not open until
the condensate temperature has dropped
below steam temperature (the exact
temperature difference being determined by
the fluid used to fill the element). This is clearly
a disadvantage if the steam trap is chosen for
an application in which water logging of the
steam space can not be tolerated, for example;
mains drainage, heat exchangers, critical
tracing.

31. Typical Application:
Steam radiators
Steam tracer and jacketed pipe .
Air venting of process equipment Steam
heater.

32. Bimetallic steam trap

33. Response of a single element
bimetal steam trap

34. Bimetal steam trap with two
leaf element

35. Response of a two leaf element

36. Multi-cross elements of
bimetallic steam traps

37. Advantages
Bimetallic steam traps are usually compact, yet
can have a large condensate capacity.
Good air venting capability and maximum
condensate discharge capacity under 'start-up'
conditions.
Bimetallic steam traps are usually able to
withstand water hammer, corrosive condensate,
and high steam pressures.
Maintenance of this type of steam trap presents
few problems, as the internals can be replaced
without removing the trap body from the line.

38. Limitations
Bimetallic steam traps are not suitable for
fitting to process plants where immediate
condensate removal is vital for maximum
output to be achieved
Bimetallic steam traps do not respond
quickly to changes in load or pressure
because the element is slow to react.

39. Bimetallic steam traps

40. Bimetallic steam trap with
cooling leg

41. Thermodynamic Steam Traps
 Traditional thermodynamic steam trap
 Impulse steam trap
 Labyrinth steam trap
 Fixed orifice traps

42. Thermodynamic steam trap

43. Advantages
They are compact, simple, lightweight and have a
large condensate capacity for their size.
Thermodynamic traps can be used on high
pressure and superheated steam and are not
affected by water hammer or vibration.
As the disc is the only moving part, maintenance
can easily be carried out without removing the
trap from the line.

44. Limitations:
Thermodynamic steam traps will not work
positively on very low differential pressures.
Thermodynamic traps can discharge a large
amount of air on 'start-up' if the inlet pressure
builds up slowly. However, rapid pressure build-
up will cause high velocity air to shut the trap in
the same way as steam, and it will 'air-bind'. In
this case a separate thermostatic air vent can be
fitted in parallel with the trap

45. Impulse steam trap

46. Advantages
Impulse traps have a substantial condensate
handling capacity for their size.
They will work over a wide range of steam
pressures without any change in valve size and
can be used on high pressure and superheated
steam.
They are good at venting air and cannot 'air-
bind'.

47. Limitations:
Impulse traps cannot give a dead tight shut-off
and will blow steam on very light loads.
They are easily affected by any dirt which enters
the trap body due to the extremely small
clearance between the piston and the cylinder.
The traps can pulsate on light load causing noise,
water hammer and even mechanical damage to
the valve itself.

48. Labyrinth steam trap

49. Advantages
This type of trap is comparatively small in
relation to its capacity and there is little
potential for mechanical failure since there
are no automatic parts.

50. Limitations:
The labyrinth trap has to be adjusted
manually whenever there is a significant
variation in either steam pressure or
condensate load

51. Ball-float steam trap

52. Bucket-type steam trap

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