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Money Trap

Proper steam trap maintenance adds dollars to the bottom line.

Jim Phillips, Executive Editor

Plant MaintenanceandEngineeringBy Jim Phillips, Executive Editor Money Trap Proper maintenance of steam traps adds dollars to the bottom line. An average textile plant may have as many as 100 to 200 steam traps as part of its steam distribution system. With an average failure rate of approximately 20 percent per year, these seemingly insignificant elements of the plants engineering profile can have a major impact on a manufacturing facilitys efficiency and bottom line.A general estimate is that a single failed steam trap can cost an average-sized textile plant a minimum of $2,000 per year in lost energy, depending upon the cost of steam. If, indeed, the 20-percent failure rate holds true, then plant engineers can expect inefficiency within the steam distribution system to cost a minimum of $40,000 to $80,000 per year for those that have 100 or 200 steam traps and maintain them on an annual basis. For a company that has a higher failure rate and there are many or more steam traps, the potential for waste is even greater.Part of the reason the potential for loss in this area is so high is that the steam distribution system is often a neglected area of plant maintenance. Many steam traps are hidden in hard-to-access areas, and the cost of testing them can be somewhat expensive. Even for companies that have an annual test-and-replace program in place, studies show the average steam trap has been leaking for more than six months before it is replaced.  The Role of the Steam Trap

The job of the steam trap is to get condensate, air and carbon dioxide (CO2) out of the system as quickly as they accumulate, according to information provided by Armstrong International Inc., Three Rivers, Mich., a manufacturer of products for steam distribution systems. For proper operation and economy within the system, steam traps must provide for minimal steam loss, as well as long life and dependable service. Rapid wear, according to Armstrong, can quickly bring a steam trap to the point of failure. Neglected traps that begin to fail deteriorate quickly. Trap parts also must be resistant to corrosion to offset potential damage as a result of condensate rich in oxygen or acidic compounds. Because steam traps are located at the lowest point in the steam system, condensate can pick up dirt and scale from the piping. Traps must be able to operate efficiently in an environment that includes this residue, as well as solids passing through the steam lines from the boiler. A properly functioning steam trap should also be able to operate against the actual back pressure in its return system.The cost of steam loss can build until it becomes a significant contributor to overall operating efficiency and profitability. Assuming that steam costs approximately $5.00 per 1,000 pounds to generate, a leak in a 1/2-inch orifice at 100 psi would generate a steam loss of approximately 835,000 pounds per month at a monthly cost of $4,175. That loss translates into $50,100 per year. A leak in a 1/8-inch orifice will waste 52,500 pounds of steam a month, representing $262.50 per month or $3,150 per year (See Table 1).There are several methods to combat the monetary losses associated with steam trap failure. The simplest, however, is the hardest for which to create a model. Optimally, plant engineers would be able to profile each type of steam trap, determine its average life cycle and replace the trap before it begins to fail. The difficulty is that different types of traps under diverse operating environments can have life spans that fluctuate. An alternative method is to inspect traps annually and replace those that are failing. The downside of this method, however, is that some losses due to trap failure are inevitable. Failures within steam traps are often internal and not readily visible without testing. The worst approach for most companies is to neglect maintenance on the steam distribution system. The costs of inspection and replacement are often insignificant compared to the value of the lost steam.
 Steam Trap TypesThere are several different types of steam traps available, and selection should be based on the ultimate operating requirements of the steam distribution system, according to Armstrong. The inverted bucket steam trap has only two moving parts the valve lever assembly and the bucket. The heart of its simple design is a unique leverage system that multiplies the force provided by the bucket to open the valve against pressure, the company states. Since the bucket is open at the bottom, it resists damage from water hammer, and wearing points are heavily reinforced for long life. Armstrong inverted bucket steam traps open and close based on the difference in density between condensate and steam. They open and close gently, minimizing wear.Float and thermostatic steam traps provide an energy-efficient option when steam pressure varies from maximum steam supply pressure to vacuum, according to Armstrong, while thermostatic wafer steam traps are geared for low-capacity steam tracers and are not generally used in applications involving process equipment. Radiator traps can be used for draining equipment such as steam radiators, convectors and small heat exchangers. Controlled disc traps, such as Armstrongs CD-40 and CD-60 models, contain a replaceable capsule that makes it possible to renew a worn trap by replacing the capsule. A heating chamber in the shell assures consistent operation and provides a relatively constant temperature in the control chamber regardless of ambient conditions.Deciding what type of steam trap to use depends upon application and environment, according to Armstrong. Factors to consider when choosing steam traps, particularly if they are to be installed and maintained internally, include condensate loads in pounds per hour, safety factors to use, pressure differential and maximum allowable pressure. February 2002