The Purpose of Steam Traps - FAQ
Following are answers to many frequently asked questions about the purpose of steam traps.
1. Is the amount of steam flowing through the air vent of a bucket trap less than the amount of steam condensed to make up for the trap's heat loss, or less than the amount of condensate flowing into the trap?
Less than the amount of steam condensed to make up for the trap's heat loss.
2. What operating principle does an F&T trap incorporate?
The principle that steam is hotter than condensate or air.
3. Is the specific purpose of the thermostatic valve in an F&T trap to handle condensate?
No.
4. Thermodynamic disc traps operate on the differences in flow dynamics between steam and condensate and on what?
A time cycle.
5. Of these four - disc, bellows, wafer and bimetallic strip - which is not a thermostatic element?
Disc.
6. What type of trap is designed expressly for use in syphon drainage applications?
The differential condensate controller.
7. What are the characteristics of an efficient steam trap?
Three key characteristics are retaining steam in the steam space, draining condensate and removing non-condensables.
8. A modulating output is the normal response of an IB trap to what?
Very light condensate loads.
9. The IB trap is characterized as having an intermittent discharge. Does this mean that the trap backs up condensate?
No.
10. What will a steam/air mix inside an F&T trap cause the thermostatic valve to do?
Open or close, depending on the ratio.
11. The period between discharges of a properly working disc trap is primarily a function of what?
Time.
12. What will a cold rain often cause a disc trap to do?
A cold rain is likely to make a disc trap cycle more often.
13. Is it true that the bleed groove in a disc trap will allow air to escape from the inlet to the outlet?
No. That is false.
14. What is the secondary discharge of a DC likely to contain?
Flash steam, and air.
15. What is one type of trap that is often used in low pressure applications where the trap never handles any condensate?
Thermostatic bellows.
16. What type of trap is commonly associated with sub-cooling condensate?
A bimetallic trap.
17. What trap type has the best ability to draw condensate from low-flow areas of the heat exchanger?
Differential condensate controller.
18. How does a properly performing steam trap maximize efficiency of the steam system?
It keeps the system filled with dry steam, it removes condensate and air from the system, and it makes hot condensate available for recycling.
19. Do mechanical traps operate using the difference in density between steam and condensate?
Yes.
20. Are there steam traps on the market today that may last forever?
No. Such a trap does not yet exist.
21. Do mechanical traps operate using the difference between hot and cold condensate?
No.
22. Is the difference in temperature between steam and condensate used to operate a thermostatic trap?
Yes.
23. Does an IB trap continuously and automatically vent air?
Yes.
24. Does an IB trap typically fail closed or open?
It is more likely to fail open.
25. In an F&T trap, will the condensate valve be water sealed during normal operation?
Yes.
26. Will a thermostatic steam trap open only in the presence of air?
No.
27. Do the thin, flexible metal parts of a thermostatic bellows stand up well in hammer?
No.
28. Must bimetallic traps be preset for the intended pressure operating range?
Yes.
29. Are differential controllers similar in construction to F&T traps?
No, they are not.
30. Will steam traps work against back pressure?
Yes.
32. Mechanical traps operate on differences in what?
They operate on differences in density.
33. What is the purpose of the bucket vent in the IB trap?
To provide continuous air venting.
34. Are IB traps in welded stainless bodies freeze damage resistant?
Yes.
35. IB traps must be primed with condensate before they will operate properly. Why is the prime needed?
To make the bucket float.
36. If a steam trap is located eight feet above the point it is draining, the load is fairly steady and complete drainage is a must, what type of trap is recommended?
A differential condensate controller trap.
37. Will excessive air in the system affect a normal inverted bucket steam trap?
Yes.
38. Does a thermostatic trap discharge condensate very near the saturated steam temperature for the pressure it's operating on?
No.
39. How does a disc trap operate?
The higher velocity of the steam across the disc face causes a pressure drop in that area, thus shutting the trap.
40. Does an F&T trap have good resistance to water hammer?
No.
41. Is a wafer trap similar to a thermostatic bellows trap in the principle on which it operates?
Yes.
42. On what principles does an F&T trap operate?
Condensate is denser than steam, air in steam will sub-cool steam below its saturation temperature, and the float rises with the condensate level in the trap to open the valve.
43. Does a bimetal thermostatic trap have a metallic element that expands or contracts with the varying temperature it senses?
Yes.
44. Does the inverted bucket trap ever have a water seal?
Yes. It can have a water seal.
45. Does the F&T have a float?
Yes.
46. How many moving parts are there on a disc trap?
One.
47. What must a steam trap remove?
Condensate, air and carbon dioxide.
48. Is the prime of an inverted bucket trap the condensate above, below or inside the bucket?
The answer is all three.
49. Can the orifices inside a disc trap become blocked by dirt and scale?
Yes. The orifices are small and can become blocked.
50. Does a trap with a longer service life cost less over its operating life than a trap with a lower acquisition cost but shorter service life?
Yes.
