Steam traps are designed to purge condensate from a steam-distribution system. Condensate is produced when hot, high-pressure steam contacts the colder pipe walls, and the temperature drops enough to cause condensation, a change of state from gas to liquid. The presence of condensate in the steam lines can cause many problems: excessive wear on valves and fittings, pitting of pipe walls and elbows, and vibration of the pipeline itself.
A steam trap in proper working order permits only liquid condensate to pass from the steam line. A trap with worn components allows live steam to escape with the liquid condensate. The quantity of steam may be small, but its loss represents a disproportionate amount of energy: the heat required to raise the temperature of water to boiling, plus the heat needed to vaporize the fluid, plus the thermal energy to increase the temperature and pressure for distribution in the steam loop.
A small steam leak may seem inconsequential, but over a long period the losses can be substantial. Thus, it’s imperative that the steam traps be kept in good repair. Leakage of steam is obvious from traps that aren’t connected to a condensate return system. For closed systems, in which the condensate is piped back to the boiler to conserve its thermal energy, the presence of steam in the condensate line is a little more difficult to detect.
The most noticeable symptom of bad steam traps with ported condensate lines is an unusually high temperature at the condensate discharge line. This happens when the steam enters the lower-pressure condensate line and its temperature increases. Infrared imagery is the most dependable way to diagnose a bad trap. A systemwide survey should be done. Many service companies use a camera with special infrared-sensitive film to find the faulty traps. A facility that has many such surveys to do on a regular basis may find it more economical to purchase the equipment and undertake the survey in-house.
A long-term option is to buy more modern replacement traps as old ones wear out. Most manufacturers market steam traps that have a built-in temperature sensor. A portable handheld meter can be connected to electrical jacks of each trap for an exact reading.
Other models have an LED that lights up when the trap requires maintenance or adjustment. These devices can later be connected to a central energy management system so that all the traps can be continuously monitored from a remote location.
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Excerpt from Energy Conservation Projects.