Steam System Management - FAQ
Following are answers to many frequently asked questions about managing a steam system.
1. What causes retained condensate to expand, possibly damaging equipment or piping?
Freezing is the culprit.
2. For water, what is the change of state between a liquid and a solid called?
Again, freezing is your answer.
3. Condensate is approximately the same temperature as steam, so what will condensate in a heat exchanger do?
It will reduce the heat transfer rate, because it is a poor heat conductor.
4. When does thermal shock occur?
Thermal shock occurs when live steam is discharged into cool condensate.
5. Can water hammer cause catastrophic failure?
It sure can.
6. Is it normally more economical to return condensate to the boiler or throw it away?
Return condensate to the boiler.
7. Is condensate incompressible?
Yes it is.
8. When steam reverts from its gaseous state, is condensate formed?
Yes.
9. Can water hammer occur only in hot water lines?
No. Water hammer can occur in other lines, as well.
10. What normally moves the condensate in a steam system?
Gravity.
11. What causes steam to condense?
Heat loss.
12. Does oxygen in a steam system slow corrosion?
No.
13. When water freezes, what happens to its volume?
The volume expands.
14. When does differential shock occur?
When a slug of condensate is accelerated by a collapsing low-pressure steam pocket.
15. What is caused by accumulations of condensate in a coil?
Corrosion is the result.
16. What causes condensate to flow through, and out of, heat exchangers?
The gravity head of the condensate.
17. What are some of the purposes of a condensate system?
A condensate system provides for efficient removal of condensate and non-condensables. It also provides for the return of hot condensate to the boiler whenever practical.
18. Is boiler makeup water normally chemically treated?
Yes.
19. What is the most prevalent source of impurities in boiler steam?
Makeup water.
20. Does the temperature of steam at a given pressure increase when air is mixed with the steam?
No.
21. Is air a very conductive medium for heat transfer?
No.
22. When allowed to cool below steam temperature, what does carbon dioxide combine with condensate to form?
Carbonic acid.
23. Do vacuum breakers eliminate air from a steam system?
No.
24. If air is undesirable, why do we use vacuum breakers to let air into the heat exchanger?
Air breaks the vacuum, which is desirable, and it brings internal pressure up to atmospheric pressure so condensate can drain out by gravity. It also helps stabilize the temperature output of the heat exchanger.
25. Why is it undesirable to have air inside a heat exhanger?
Because it acts as an insulator.
26. Is nitrogen responsible for corrosion in steam systems?
No.
27. Are air vents the most common source of air in a steam system?
No. Vacuum breakers are the most common.
28. What are some of the problems that arise in a steam system if condensate is not removed properly?
Freezing, water hammer and corrosion are the three main problems.
29. What types of shock can cause water hammer?
Hydraulic, thermal and differential shock can cause water hammer.
30. What is water formed when steam reverts from its gaseous state to a liquid?
Condensate.
