Preventing steam trap failures

Properly functioning steam traps open to release condensate and automatically close when steam is present. Failed traps waste fuel, reduce efficiency, increase production costs and compromise the overall integrity of the steam and condensate systems. Traps should be tested regularly, or the neglect may be quite costly.

03/01/2010


 

Properly functioning steam traps open to release condensate and automatically close when steam is present. Failed traps waste fuel, reduce efficiency, increase production costs and compromise the overall integrity of the steam and condensate systems. Traps should be tested regularly, or the neglect may be quite costly.

Steam energy conservation is important to our national interest. Consider these statistics from the U.S. Dept. of Energy, Energy Efficiency and Renewable Energy:

  • More than 45% of all the fuel burned by U.S. manufacturers is consumed to raise steam. Steam is used to heat raw materials and treat semi-finished products. It is also a power source for equipment, building heat and electricity generation. But steam is not free. It costs approximately $18 billion annually to feed the boilers generating steam.

  • Many manufacturing facilities can recapture energy through the installation of more efficient steam equipment and processes. A typical industrial facility can realize steam savings of 20% by improving their steam system. If steam system improvement were adopted industry-wide, the benefits would be $4 billion in fuel cost reduction and 32 million metric tons of emission reductions.

    • Why do steam traps fail?

      Obviously, anything mechanical will malfunction; steam traps are no exception. However, proper maintenance improves longevity and helps reduce maintenance costs. There are three general conditions that adversely affect traps:

      1. Dirt is, by far, the leading cause of failure resulting in either a leaking or plugged trap.

      2. Pressure surges (due to sudden steam valve openings, improper piping or trap misapplications) can result in water-hammer and subsequent damage to the internal steam trap components.

      3. Oversizing IB traps can lose their prime; TD traps can experience rapid cycling.

        1. How do we keep problems to a minimum and keep energy costs in check? One simple way is to look for warning signs. The seven most evident signs that should signal a distress call from your steam system include:

          1. The once lazy plume from your condensate stacks is now an out of control freight train. The steam that is standing at attention from your stack, like a soldier standing at attention, is costing you dearly.

          2. Condensate back pressures that have slowly been rising have been causing your electric condensate pump to self destruct. High-temperature condensate cannot be handled by conventional electric pumps. Temperatures greater than 212 F cause conventional electric condensate return pumps to cavitate. Motors burn out and mechanical seals begin to leak when steam is present.

          3. Pressure reducing valves (PRVs) or control valves fail to maintain set pressures. Fully- or partially-plugged traps prevent condensate from being eliminated from the steam space. Un-drained condensate at PRV stations will back up into the steam line and will wiredraw the heads and seats of the reducing valves. Wiredrawing is when high velocity water in the steam system cuts (scores) the surfaces of heads and seats. Even small microscopic cuts will prevent the proper operation of these valves.

          4. Production capability has been reduced. Open or closed traps that have failed will negatively impact production. Plugged traps will back condensate up into the process and dramatically reduce system efficiency. Blowing and leaking traps are costly to production due the added and unnecessary energy consumption.

          5. Pipe wall thickness of the condensate system has become an issue. Fully open or partially opened steam traps that are not repaired in a timely manner will deteriorate the condensate return piping. Some of the early warning signs begin with steam leaks.

          6. The cost to maintain heat exchanger bundles, humidifiers, HVAC coils and other equipment has dramatically increased. Failed traps will prevent proper operation of sensitive equipment. When steam traps fail in a closed position, over time, the stagnant condensate will turn to carbonic acid (CO3), which deteriorates any metal it comes in contact with. Beyond increased energy consumption, failed open traps will also cause control and efficiency issues.

          7. Water hammer can develop in neglected or mismanaged steam and condensate systems. Water hammer literally sounds like someone is hitting a pipe with a hammer. In some cases, water hammer can occur when a portion of the steam condenses into water within steam piping. Left un-drained, condensate will spill into the steam system and begin to accumulate. Eventually, a wave of water will be created. This slug of water can be carried at high velocity until it reaches an obstruction like a closed valve, a lower elevation or a sudden change of direction.

            1. A trap that is blowing steam can also cause water hammer. Blowing traps create back pressure in the condensate system piping. If condensate piping is already undersized, the problem will be compounded by the additional pressures found by the faulty traps. Un-drained condensate can back up into the steam distribution piping. From the standpoint of plant safety, it is essential to test and maintain the steam trap population. Type “steam water hammer accidents and fatalities” into a search engine; the results should be convincing enough to create an immediate action plan.

              Action plan

              The following actions can help ensure that your steam traps are operating properly: