At our first eChemExpo FieldNotes Lunch and Learn, which I co-hosted with Scott Owens, chair of eChemExpo’s advisory board, mechanical engineer Bo Pless walked us through a practical guide to steam traps: what goes into selection, sizing and troubleshooting.

Pless described a steam trap simply as a valve that controls when flow happens and what kind of flow passes. Traps are small, but their failures are costly. In his example, 10 failed traps with one-eighth-inch orifices in a 100-trap facility waste nearly 7 million pounds of steam a year, costing about $40,000. Failed traps can also cause safety and operational problems.

He then reviewed the main trap types:

• Thermodynamic disc traps are cheap and easy to replace, which suits low-flow uses like drip legs and tracing.
• Thermostatic traps respond to temperature, so they fit superheated steam or tracing with subcooled condensate.
• Float traps are the workhorse. They purge continuously, which suits process equipment such as heaters and dryers.
• Inverted bucket traps need a liquid prime at startup but handle high flow and high pressure together economically.
• Orifice traps are inexpensive and high-capacity but work well only at a constant operating point.

For troubleshooting, Pless recommended two basic tools: an infrared thermometer and an ultrasonic listening device. He described three failure modes:

• Failed open. The trap blows live steam through. The control valve opens fully, chest pressure nears header pressure, and the discharge shows a high-velocity jet of clear vapor. Temperature won't reveal this failure, but ultrasound will. The trap must be replaced or rebuilt.
• Failed closed. Condensate backs up into the exchanger and chest pressure drops. Drains run liquid for a long time and downstream piping stays cold, so temperature is the key clue.
• Stall. The symptoms look identical to a failed-closed trap, but the trap isn't at fault. The cause is insufficient differential pressure, from excessive back pressure (such as lifting condensate to an overhead rack) or overestimated upstream pressure. Stacked safety factors can produce an oversized exchanger that pulls a vacuum. A pump trap, using motive steam 20 to 40 psi above operating pressure, can fix stall.

In the Q&A, Pless said common causes, like dirt or a trap installed backward, are usually the culprit. He urged process engineers to inspect before replacing a trap and to involve steam specialists early in piping design. He also advised using orifice traps only for steady loads, since they are hard to troubleshoot.

eChemExpo FieldNotes Lunch and Learn sessions will be held on the last Thursday of each month on LinkedIn. It's our way of keeping the eChemExpo experience fresh and meaningful until we meet again in person in April 2028 in Kingsport, Tennessee.

The next Lunch and Learn is Oct. 29. Across chemical, refining, power, steel and petrochemical operations, water and steam systems keep processes running. Yet cooling water systems get little attention until fouling, corrosion or biological growth causes serious problems. Expert Brad Buecker will explore:

• How biofilm, scale, and corrosion interact in the cooling water control triangle
• Field-tested lessons rarely taught in engineering school

Sign up for this session here.