There are many different styles of steam traps but they all serve the same basic purpose; to automatically allow condensed and non-condensable gases like air to escape while maintaining an efficient thermal transfer process.  Most traps function while remaining closed to live steam but some use simple control valves to pass steam at a regulated rate.

With a fuller understanding of steam traps basics maintenance personnel are better equipped to inspect traps throughout the facility using common methods.

1.Visual Inspection
In a visual inspection the operator will check that the discharge valve is functioning.  This requires venting live steam to atmosphere and can pose safety issues.  Because it opens the closed portion of the system it is not a 100% reliable test.  Visual inspection is important because a trained operator can look for potential problems in engineering and design that can lead to trap failures.

2.Thermal Inspection
Another method for routine testing of traps is with contact or non-contact temperature checks.  Upstream and downstream temperature checks can reveal failed open traps.  But variables such as back pressure in the system can make temperature checks less accurate.  Thermal inspections are useful for identifying heat loss, overloads, and pressure build-ups.  Relying on thermal inspections alone doesn't capture the entire picture.

3.Ultrasonic Inspection
Ultrasonic testing ties all other inspections together and makes sure nothing is missed.  Take for example the thermal image below, supplied to us by Absolute Infrared Inspection Services of Erie, PA.  The image was captured by Level II Infrared inspector Craig Casler who provides various PdM surveys throughout the North East.

Thermal Image - Trap appears okay

Digital Image of trap

Going by the thermal image only the trap appears okay. Casler does thorough work when he provide inspection services and decided to also listen to the ultrasonic signature of this trap. Using his SDT 170MD equipped with contact probe we recorded this sound file for us. Clearly, this trap has failed mechanically and is not performing its function.

Its a great example of how combined predictive technologies such as Infrared, Vibration, and Ultrasound each compliment one another to provide a more clear and accurate account of the state of your plant's health.
 

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