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What's a steam trap?
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.
Testing Methods for Steam Traps
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.
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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.
Click here to learn more about
the SDT 170S+ Digital Steam Trap Inspector's Kit |
