Maintaining Steam Traps
Failed steam traps waste energy and adversely affect product quality. Therefore, a maintenance program for
steam traps is a good investment.
Most plant and facilities professionals with steam systems in their care have asked questions like the
• What are the signs of a malfunctioning steam trap?
• What inspection techniques are available?
• What testing instruments should we use?
• How do we start a steam trap maintenance management program?
• What kind of training resources are required?
Steam Trap Basics
Basically, all steam traps have the same function. They allow condensate and non-condensable gases to
escape while holding steam in a device where a thermal or heat transfer process occurs. A regulator
controls the input side of the process, and the steam, after releasing energy to the process, condenses and
reverts back to its liquid state. The purpose of the steam trap is to retain steam in the heating element and to
release the non-condensable gases and condensate. The principal design consideration is to balance the
condensing rate and the import rate of the control device on the input side with the exiting condensate.
Properly sized traps relieve the condensate, react quickly to changes in load, and trap the steam while
allowing air and other non-condensable gases to escape.
Finding Malfunctioning Traps
As with any mechanical device, a steam trap can malfunction. If the steam trap fails closed, the device that
should be draining will flood, the heat transfer process will stop, and whatever product is being produced will
no longer be up to the required quality standards. If the trap fails open, there will be a waste of energy, steam
will not be completely consumed or condensed in the exchanger, and steam will blow through. It should be
noted that a plume of steam escaping from some part of the condensate-return system signals such a
condition. It is difficult to determine whether a steam trap has failed just partially open, indicating a slow leak
and a developing failure. Such a failure could persist for quite some time without any outward sign.
Therefore, a maintenance person should make periodic surveys of the installed base of steam traps. We
emphasize that steam blowing through a trap indicates that the trap needs to be repaired or replaced.
Trap Inspection Methods
Oftentimes, a misapplied steam trap—too small, the wrong design—will malfunction. Ultrasonic, infrared
temperature measurements, and visual inspection have proven useful to maintenance personnel in
checking for malfunctioning steam traps with ultrasound being most reliable. There are enough variables in
the system (back pressure, for example) so that temperature is not the most reliable indicator. Portable
infrared thermometers provide close estimations of pressures on valves, traps, and coil heaters. These
devices are also useful for spotting conditions such as heat loss, the need for insulation, overheating,
overloads, and cooling failures. Thus, we recommend that an infrared thermometer be used along with
Traps that have failed completely open are easy to detect, the object is to find failing traps before they fail
completely. Ultrasonic testing can do that. "In essence, using an ultrasonic instrument allows us to inspect
inside the steam trap and piping system, allowing us detect a leaking steam trap, Ultrasonic detectors
translate ultrasonic emissions into sounds the human ear can hear.” Technicians who use ultrasonic
detectors on a daily basis can achieve accuracy that exceeds 98%. And regarding frequency of inspections,
we recommend that process components of equipment as well as drip, main steam traps should be
checked twice a year. Heating steam traps (in facilities that use steam for space heating) should be tested
annually. And stress the importance of instituting a reporting system to keep tabs on the location, type, size,
capacity, and condition of all traps in a steam system.
Creating A Maintenance Program
A steam system maintenance program should provide total-system training and include a reference manual
written for plant personnel so they will have a reliable guide for the future. On-site work-shops include a plant
audit and that personnel be shown how to collect data for their own predictive maintenance program.
Correcting the problems and energy losses documented during the initial audit will pay for the costs of the
consultants/instructors within months.
For a maintenance management program to work, it is imperative to identify and document all components
in both the steam system and the condensate return system. Steam systems are often a maze of lines
going in every direction. Most have been modified over the years, and maintenance personnel probably have
no idea how steam is distributed throughout the plant.
When blueprints do exist, they should be studied to get a full understanding of the steam system, the
distribution of piping, and the placement of critical equipment such as valves and traps. If there are no
drawings, new ones should be created. Blueprints should depict the entire system, including boilers, main
distribution lines, and the heat-transfer system. These plans need not be full isometric presentations; flow
diagrams are sufficient for 90% of a facility's operation. In addition, the locations of heat exchangers, steam
traps and valves should be included for future surveys.
"A steam trap maintenance management program can pay for itself in less than a year. And the savings will
multiply as the years pass."