Steam trap failure is a topic of worry for many plant managers. Failure of steam traps hampers the performance of steam system and is a safety hazard as well. There might be numerous reasons which cause steam trap failure. It would be worthwhile to go through a few of them and understand how one can avoid them.
When steam leaves the boiler house, it is mostly dry steam. As steam passes through the pipe-work, radiation losses take place and condensate is formed. During the heating applications, steam loses its heat to the products being heated and as a result, condensate is formed. Steam traps do the important task of removing this condensate as soon as it is formed.
Steam trap failure results in improper removal of the condensate. Some steam systems have an annual steam trap failure rate of as high as 35%. Hence, understanding the reasons for failure of steam traps is important. Following are the factors that cause the steam traps to fail or expedite the failure of steam traps.
Feed water contamination
Quality of feed water plays a major role in determining the life of steam systems and components installed. If feed water has dissolved gases like oxygen or carbon dioxide, corrosion of steam traps and other components will take place. Oxygen results in pitting whereas carbon dioxide dissolves in condensate to form carbonic acid which turns the condensate acidic.
Improper feed water treatment also results in carryover which also contributes to steam trap failure.
Steam traps should be sized correctly. Undersized steam traps tend to fail faster compared to the correctly sized steam traps. It is a common mistake to size the steam traps based on condensate formed during the running mode. One must take into consideration the start-up condensate formation load while sizing the steam traps.
Incorrect installation of steam traps
The operating life of steam traps gets significantly reduced if they are not installed correctly, keeping in mind the recommended installation guidelines. For instance, a strainer should be installed upstream of every steam trap. While some steam traps have inbuilt strainers, for some steam traps, a separate strainer needs to be installed before the steam trap.
Absence of the strainer might result in entrainment of rust or other debris inside the trap and the trap internals might get damaged.
Thermodynamic steam traps, when used in extremely cold weather, should be installed with insulating caps to avoid rapid cycling, also called as ‘chattering’. Rapid cycling results in fast wear and tear of the disc and the seat.
Improper maintenance practices or lack of maintenance
Every steam trap needs the right kind of maintenance. It has been observed that at many plants, steam trap maintenance is either improperly carried out or is completely missing. In fact, every steam system should have its own maintenance calendar which should be strictly followed.
Maintenance helps identifying problems right at the beginning and avoids their aggravation. Maintenance and inspection can give insight into other problems (visual signs like corrosion) that might lead to the failure of steam traps.
Contamination of condensate
Leakage in the heat exchangers or use of multiple utilities results in condensate contamination. Contamination of condensate can reduce its pH and turn it acidic. Acidic condensate corrodes the internals of the steam traps and hence, is a reason why steam traps fail.
Selecting a wrong type of steam trap
Steam trap selection is probably the most crucial step which determines the performance as well as operating life of a steam trap. Many times, it is observed that a wrong kind of steam trap is installed on a wrong application. The result is lowered life of the steam trap.
Avoiding the issues mentioned above will significantly improve performance and operating life of steam traps. Do you think we have missed anything? Please share with us in the comment box below.