Savvy maintenance teams are consistent and persistent in following a protocol that monitors plant steam systems. According to a Steam Trap Inspection Guide from UE Systems (Elmsford, NY) these systems should be inspected routinely—and for good reason: Faulty steam traps not only waste energy, they can contribute to pipe erosion, negatively affect product quality in various processes, and even play a role in environmental pollution.
To be clear, the frequency of steam-trap inspections is often determined by application. For example, steam systems used just for facility comfort, i.e. heating, are usually inspected annually (in the fall), while those associated with production operations might be inspected biannually or quarterly, depending on the impact of steam on the process.
Ultrasonic testers translate the high-frequency emissions of a trap down into the audible range where they are heard through headphones and seen as intensity increments on a meter. Some units have frequency tuning to filter out additional signals and to tune into the sounds of steam and condensate while others have on-board recording and data logging.
Although there are a variety of trap designs, for purposes of inspection, there are basically two main types: continuous flow and intermittent (on/off). Each type has its own unique pattern. It’s important to listen to a number of traps to determine a “normal” operation in a particular situation before proceeding with a survey. Generally, when checking a trap ultrasonically, a continuous rushing sound will be the key indicator of live steam passing through.
The most common method for ultrasonically testing a steam trap is to touch it on the downstream side. The technician should then adjust the sensitivity to the point where the trap sounds are capable of being heard. This is usually a setting at which the meter’s intensity indicator is in a mid-line position. Adjusting the sensitivity to levels that are either too low or too high will make the trap sounds difficult to hear. If frequency tuning is available on the instrument, choose 25 kHz.
• Since ultrasonic testing of steam traps is a positive test, it provides results in real time. The main advantage of this technique is that it isolates the tested area by eliminating confusing background noises. Personnel, in turn, can quickly adjust to recognizing differences among various traps.
• While performing a steam-trap survey, it’s important to note specific trap conditions on a chart. Every trap should have a tag with a corresponding identification code. Poorly operating units should be documented in a non-compliance report and follow-up procedures planned. Be sure to include digital photographs of traps. These reports should reference items such as trap number, condition, and date of repair.
• As part of a quality-assurance procedure, all repaired traps should be scheduled for re-test. A comprehensive report describing the results of a steam-trap survey is recommended. This report should include items such as the number of traps tested, the number found in good condition, and the number of faulty ones. A cost analysis indicating the gross amount of savings, repair costs, and net savings associated with the survey should also be included.
Keep in mind
Any steam system can leak, and any trap can potentially waste steam. If performed properly, a routine, planned program of steam-trap inspection and repair can continually pay for itself and contribute to a company’s bottom line in terms of productivity, quality, and energy savings. MT
For information and registration details regarding UE Systems’ September 2017 webinar series on steam-system inspections, email Adrian Messer at firstname.lastname@example.org, or telephone 914-282-3504.