Steam Trap Testing at a Power Plant: TRAPChecker + SDT270

Why test steam traps

A steam trap discharges condensate and holds back steam. What happens when it fails depends on the failure mode:

• Failed open traps pass live steam into the condensate line. That is a direct loss of steam and fuel, and condensate system pressure rises.
• Failed closed (blocked) traps do not discharge condensate. Heat exchanger output drops and water hammer becomes possible.

Route-based checks use TRAPChecker or the SDT270 and SDT340 ultrasonic detectors. See also the steam and condensate section of the SDT catalogue.

Test method

1. Ultrasound

Press the contact sensor against the trap body just downstream of the inlet. The sound and its pattern show the condition:

Condition	What you hear
Working (cycling type)	clear cycles: open, discharge, close
Failed open	continuous steam flow noise with no pauses
Failed closed	silence or a very weak signal on a hot line

Trap type matters: thermodynamic, float and thermostatic traps sound different, so compare against a working trap of the same type on a neighbouring line.

2. Temperature

Measure temperature upstream and downstream of the trap. A cold inlet on a live line points to a blocked trap or a closed valve. Temperature alone cannot tell a failed-open trap from a working one, so it only confirms the ultrasound result.

3. Documentation

Give every trap a number and a tag, and record its type, pressure, condition and signal recording. The SDT270 and SDT340 store measurements in a route, so surveys can be compared over time.

Estimating steam losses

Loss through a failed-open trap depends on pressure, orifice size and wear. The estimate is:

annual loss = steam flow through the trap (kg/h) × operating hours per year × cost per tonne of steam

Worked example: a trap passes 10 kg/h of steam and runs 8,000 hours a year. That is 80 t of steam per year. Multiply by your plant's steam cost to get the loss for that one trap. The sum across all failed-open traps is the figure that justifies repairs.

Take the flow for a specific trap from the trap manufacturer's tables for its pressure and orifice size, not from averages.

A regular programme

1. Initial survey of all traps, with numbering.
2. Replace failed-open and repair failed-closed traps, then recheck after repair.
3. Periodic checks: more often on critical lines, less often elsewhere, guided by failure history.
4. A database for every trap: type, installation date, condition history.
5. Staff training in using the ultrasonic detector and interpreting signals.

Summary

Ultrasound finds both failed-open and failed-closed traps in seconds per point, and temperature confirms the result. A regular survey backed by a database turns testing into a managed programme: you can see where steam is lost and which repair pays back first. KEG TRK supplies SDT detectors and trains staff; instrument prices on request.