DLI's Drycleaning Blog

Q&A and Useful Industry Information

E-mail any question to Techline@DLIonline.org.

Checking for Leaky Steam Traps

expert.steam.trap.jpgSteam traps found in drycleaning plants should have an inlet temperature of about 300 degrees Fahrenheit and an outlet temperature of about 225 degrees F—a difference of about 75 degrees F. There are several ways to check for leaks in steam traps, including the use of laser thermometers, wax sticks, temperature indicator paper, and pyrometers.

Laser Thermometer
Point the laser at the pipe close to the inlet and outlet areas on the steam trap. There should be a difference of at least 75 degrees F between the inlet temperature and the outlet temperature. If the difference is less than 75 degrees F then the trap should be repaired or replaced.

Wax Stick

Wax sticks are temperature indicator crayons made of different types of waxes that melt at different temperatures. Wax sticks that melt at approximately 294 degrees F are usually considered appropriate for use in the testing of steam traps. This is accomplished by placing a wax mark, usually by stroking the pipe with the wax stick, on the return pipe or outlet side of the trap before heating begins. The temperature of the return pipe should be about 75 degrees F less than the inlet pipe. If the wax mark does not melt, the trap is operating properly, and no adjustment or replacement is necessary. However, if the wax mark melts, the steam trap is not operating properly, and steam is blowing through.

Paper Indicator
Another method of checking for leaky steam traps is the use of paper temperature indicators. Like the wax sticks, the paper indicators come in a wide range of temperatures, and you should choose the one that is closest to the temperature of the steam pipes (300 degrees F). Place the indicator on the hot surface of the return pipe. If the trap is working correctly, there will be no visible color change on the paper. However, if the paper blackens, steam is blowing through.


The steam trap may also be tested with the use of a pyrometer, which is similar to a thermometer. Place the metal probe of the pyrometer against the pipe, and it will measure the temperature of the metal and display it on a gauge. In the past, pyrometers were generally used for measuring extremely high temperatures, but they can now be used for all temperature ranges.

Whichever method you use, check all the traps. Don’t forget to check the trap on the main steam header. This trap is quite often the culprit.

DLI has several resources to help with this sort of issue. Technical Bulletins: "Characteristics of Steam and its Trapping System" and "Eight Simple Energy Savers" in DLI's Encyclopedia of Drycleaning offer a wealth of information on this topic. Bruce Grossman's Fabricare membership magazine articles cover all sorts of DIY maintenance issues as well.

Posted By Harry Kimmel | 2/8/2018 10:27:05 AM