Failed steam traps waste and adversely affect product quality.  Therefore, a maintenance program for steam traps is a good investment.

Gary W. Mohr, UE Systems, Inc.

Most plant and facilities professionals with steam systems in their care have asked questions like the following: What are the signs of a malfunctioning steam trap?  How often should traps be inspected?  What inspection techniques are available? What testing instruments should we use? How do we start a steam trap maintenance program?  What kind of training resources are required?

Steam trap basics
Basically all steam traps have the same functions.   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.

Ultrasonic detectors translate ultrasonic emissions into sounds the human ear can hear, allowing technicians to detect failing steam traps before they fail completely.

Stephen Banyacski president of Nicholson Steam traps (Walden, NY) emphasizes the need to choose the appropriate steam trap.   "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," he says.

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 and 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."  Banyacski notes that a plume of steam escaping from the condensate receiver or from some part of the condensate return system signals such a condition.

He adds that 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.  Banyacski emphasizes 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.  Ultrasonics, infrared temperature measurements and visual inspection have proven useful to maintenance personnel in checking for malfunctioning steam traps. Of the three, ultrasound is the most reliable.  Visual inspection requires an inspector to let a steam trap discharge to atmosphere. However, doing that changes the parameters of the closed system and, therefore, can be unreliable.

There are enough variables in the system - back pressure, for example - so that temperature is not the most reliable indicator either.  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, an infrared thermometer be used along with ultrasound.

Traps that have failed completely open are easy to detect, but the object is to find failing traps before they fail completely.  Ultrasonic testing can do that.  In essence, using an ultrasonic instrument is like putting the inspector inside the steam trap and piping system allowing him to 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, process components of equipment, as well as drip main stream traps should be checked twice a year.  Heating  steam traps (in facilities that use steam for space heating) should be tested annually and instituting a reporting system to keep tabs on the location, type, size, capacity and condition of all traps in a steam system is imperative.

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.  Ideally, the program will also include videotapes to illustrate troubleshooting techniques and applications.

On-site workshops should also 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.

Documentation
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.

Therefore ... when blueprints 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, locations of heat exchangers, steam traps and valves should be included for future surveys.   All devices should be tagged with identifying numbers which are then recorded on a plant map.

Finally, the most important aspect of a preventive maintenance program is an information system that allows analysis and extrapolation.  Ideally, a software system should accommodate steam traps, control valves, safety valves, check valves, and so forth.   This information should be stored for reporting and, more importantly, for analysis."

Why go through the hard work of setting up a maintenance program for steam traps?  A steam trap maintenance management program can pay for itself in less than a year.  And the savings will multiply as the years pass.