Many commercial and industrial buildings use steam systems to provide intense heat where needed, often over a great distance. As with everything in life, it’s not a perfect system and along the way steam can condense back into water and create what is known as condensate. This condensate, along with impurities and gasses, must be removed to maintain efficiency and ensure the safe long life of the system. This task is the job of the steam trap. Proper trap maintenance, beginning with a survey and inspection, ensures costs are contained now and in the future.
WHAT IS A STEAM TRAP?
There are many types of steam traps depending on the demands of the system. But they all perform the same job. They are automatic valves that release condensate while minimizing live steam loss. The majority of steam traps have moving parts and a float bowl. The condensate collects in the bowl and periodically flushes out of the trap by opening a valve. Otherwise, the valve keeps the trap sealed and the live steam contained in the system.
Moving parts can fail and the components of a steam trap are no exception. So the valve can fail open, closed or somewhere in between. Failed open causes excessive energy use, noise and unnecessary heat/steam in the condensate return lines. Failed closed causes the condensate to build up inside the trap, backing up and flooding the heat exchanger – rendering it inoperable. Condensate can also back up into the main steam header under this condition. This condensate reduces the efficiency of the system and if picked up with the moving steam in the main, can caused a condition called “water hammer”- that can be very damaging to the system. A valve stuck partially open has the potential to both waste heat and not allow enough condensate to drain.
WHAT ARE THE OPERATING COSTS OF A FAILED STEAM TRAP?
Traps that are failed open allow live steam to escape, causing both energy loss and elevated operating costs. Multiply this condition by several traps – which can number into the hundreds – and building owners and management companies face significant unnecessary expenses. More natural gas or electricity is used by the boiler to produce more steam to make up for the leaking traps. The boilers may be able to provide enough steam to make up for the leaks. Or the system operator may have cold spaces or processes that cannot run at full speed because the needed steam energy has leaked out somewhere else.
Traps that are failed closed do not allow steam to escape. But they do affect the efficiency of the system because the space in the pipe that should contain high energy steam is filled with low energy condensate. Equipment will have a lower output or the boiler will work harder to catch up, or both. Another issue is the condensate will be traveling in the system, often at high speeds. A slug of condensate can be very destructive to the system by slamming into components. This condition is known as hydraulic shock, or water hammer, as mentioned above. Resulting problems can range from annoying noise and vibration in the pipes to a rupture of the pipes. A pipe rupture is extremely expensive, requiring not only a shut down and repair of the system but also repair of steam and water damage to the surrounding area. It is a safety issue and may cause injury to people in the area.
HOW WILL A STEAM TRAP SURVEY WORK FOR ME?
The US Department of Energy reports that steam systems which haven’t been maintained in the last 3 to 5 years are likely to have up to 30 percent of their taps fail. Routine steam trap surveys and inspections help mitigate costs by finding issues before they have a chance to become something worse.
Remember, these tests have to be performed while the system is running and producing steam. So it’s important to coordinate the survey with the system operator. Failed traps are usually replaced when the system is off-line. Or, if the designer was wise enough to install valves to isolate the traps, the valves can be closed and trap replacement can happen while the rest of the system is operational. A great example is space heating systems. Test them in the early spring just before the system is turned off. Then replace the bad traps right after the shut down so the system is ready for the next heating season.
During the survey process, each trap is mapped out, tagged and assessed to determine how well it is functioning. The assessment is usually done one of three ways – visual, thermographic or ultrasonic – and each method has its own characteristics. Essentially, the technician is checking to see if the trap is working correctly and, if not, did it fail in the open or closed position.
WHAT ARE THE SURVEY TEST METHODS?
A visual inspection involves looking at condensate return receiver tank. The technician has to be able to tell the difference between flash and live steam coming from the tank’s open vent line. Flash is made when the condensate quickly expands because of atmospheric pressure, which is normal. Live steam would indicate a trap that failed in the open position.
Temperature readings provide important information for trap evaluation. A Thermal Imaging Camera is used to observe the temperature and internal workings of the trap. Trap temperatures, in relation to the pipes leading to and going away from the trap can instantly be analyzed. Since the camera can be used some distance from the trap, this method is useful when it’s not practical to be close to the trap as needed with other methods.
A cold trap, one that is significantly cooler than the pipes, shows that the trap has failed in the closed position and is likely filled with condensate. A trap with a temperature that is the same as the nearby pipes can have one of two conditions. It can either be operating properly or it can be failed open and releasing live steam. In this case, further evaluation is needed.
The flow of steam through a trap generates both sonic (audible) and ultrasonic (inaudible) sounds. With the right equipment, a technician can hear theses sounds and be able to assess the health of the trap. Much like a doctor’s stethoscope, ultrasonic detectors amplify signals and translate them into a sound the tech can hear and evaluate. Not only will they hear the steam flowing through the trap, they can also hear how the mechanicals inside the trap are working. The ultrasonic method has normally been the preferred procedure for years, but the Thermal Imaging Camera has been taking over as the optimum method for accurate steam trap diagnostics.
WHAT ARE THE BENEFITS OF A ROUTINE STEAM TRAP SURVEY?
Future cost savings as well as preventing potential catastrophic failures in the future are the biggest benefits to having a steam trap survey and inspection completed.
For instance, in a building where the cost to produce steam is $10.00 per 1000 lb/hr., an inspection reveals that a trap on a 15-pound-per-square-inch gauge (psig) steam line is failed in the open position, with a trap orifice of 1/8-inch in diameter. The US Department of Energy guide states that the estimated steam loss is 13.7 pounds per hour. If we assume the system operates continuously (8760 hours/year), repairing one failed trap results in a savings of $1,200 per year. Yes – that’s the savings for repairing just one failed trap. If there are 500 traps and thirty percent of them are bad, that results in an annual energy savings of $180,000. Remember, most of the numbers used in the example are very conservative and the savings potential for higher pressures or larger trap orifices are much higher. So, knowing how your traps are performing with a survey pays off.
In many locations, utility companies offer financial incentives to repair or upgrade faulty equipment. The steam trap is no exception and the incentive amounts often reflect the excellent energy savings. Incentive programs may require a survey and/or replacement of the failed traps within a certain time frame. Check out DSIRE for the incentives available throughout the USA and be sure to follow the requirements for the incentive program in your area.
CONTACT AMERICAN COMBUSTION TO SURVEY AND MAINTAIN YOUR STEAM TRAPS
American Combustion Service, Inc. routinely performs steam system inspections for our customers. We tag all traps, write up our findings in a full report and provide photos and a map of all the traps in the facility.
Any traps that have failed will be noted, as well as any aging equipment that may not last much longer. Inspecting traps annually is ideal, with no more than three years in between inspections at the most. In the end, it’s a simple formula – do a survey, replace failed equipment and save energy and money. We have expertise with the equipment and experience with incentive programs. We can also help you with incentive program paperwork.
We look forward to building long-lasting relationships with all our clients. Call (773) 737-9200 today to plan your steam trap maintenance program.