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In order to increase the accuracy of thermographic inspections of steam traps, contact ultrasonic testing should be used as well as infrared imaging. Contact ultrasonics are much more sensitive to trap failures than temperature measurement alone.

Over time, two different non-destructive technologies have been employed to test steam systems – contact ultrasonics and temperature measurement. Used individually, each of these techniques has limitations that can lead to false positive and/or false negative results. Combining temperature measurement with ultrasound can result in a highly accurate test method by following a few simple steps:

• Measure trap inlet to ensure that temperature is above 212º F. If trap inlet is below 212º F, ascertain why steam is not reaching trap
• Listen to the trap outlet with contact probe of ultrasonic unit. Continuous hissing or rushing sounds usually indicate a failed trap
• Ascertain that trap is cycling periodically. Frequent cycling may be caused by an undersized or worn trap
• Tag defective traps and document in a written report
• Re-test defective traps after repair to ensure the effectiveness of repairs

While it takes some practice to become proficient with ultrasonic testing, the increased accuracy is worth the effort. Lastly, always be sure to follow appropriate safety precautions especially when working with high pressure steam or when using ladders or lift equipment.

Infrared inspection of steam traps is one of the many topics covered in the Level I Infraspection Institute Certified Infrared Thermographer® training course. For information on thermographer training including course locations and dates, visit us online at www.infraspection.com or call us at 609-239-4788.