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Steam Distribution Systems

Operation and Maintenance Tips

Reduce leaks
Insulate
Remove unused piping
Ensure proper pipe sizing
Check and repair steam traps
Flash high-pressure condensate
Assess end-use needs

  • Reduce leaks: Steam leaks can often go undetected in underground distribution pipes. Monitor blowdown and feedwater to detect such leaks and make necessary repairs immediately. Large systems may justify the installation of flow monitors (or insertion points for short-term monitoring) at intermediate locations to pinpoint leaks.

  • Insulate: A great deal of heat energy can be lost through the piping distribution system. Unless the piping passes only through areas that require heating, losses can be significant. Adding 2.5 cm (1 in.) of insulation can reduce heat loss by 80 to 90 percent. Older insulation is often damaged or removed during maintenance to valves and fittings. Removable insulation pads can cover areas where maintenance is required.

    Removable pads can cover almost any surface. The 3E Plus® Insulation Thickness Computer Program is a free software tool developed by the North American Insulation Manufacturers Association to simplify the task of determining how much insulation is necessary to use less energy, reduce plant emissions and improve process efficiency.

  • Remove unused piping: Because boilers have such a long life, it is not uncommon for a facility to be renovated during the lifetime of the boiler. Old equipment may be removed, or newer piping may simply be added to the old distribution system. These actions often result in redundant piping or unused lines. Remove any older, redundant piping and isolate steam from unused lines.

  • Ensure proper pipe sizing: If the pipes have too small a diameter for the flow rate, the pressure drop along the pipe may result in too little pressure or too low a flow rate for the end use. Ensure that the distribution system piping is sized correctly to produce the appropriate system pressure drops.

  • Check and repair steam traps: Steam traps are an essential part of steam distribution systems (except for one-pipe heating systems, which do not utilize traps). A steam trap is an automatic valve that can distinguish between steam and condensate or other fluids. Steam traps discharge the condensate that can build up due to unavoidable heat losses through the piping. It is important to remove condensate from the system for a number of reasons:

    • condensate in the end-use (terminal) equipment reduces the heat transfer surface
    • condensate is corrosive and can be harmful to the end-use equipment
    • if condensate accumulates, it can be pushed by the fast-moving steam and cause water hammer

    Steam traps fail at the rate of approximately 25 percent a year. A good maintenance program includes inspections for failures.

    Steam traps must also be the right size. Undersized traps can result in condensate backup and excessive cycling. If an oversized trap fails, excessive amounts of steam can be lost. The size and pressure of a distribution system determines how often to check for failed steam traps. In general, a high-pressure system should be checked weekly or monthly; a low-pressure system can be checked annually.

  • Flash high-pressure condensate: One low-cost way of meeting part of process requirements is by "flashing" high-pressure condensate to generate low-pressure steam. Reducing the pressure causes the condensate to turn into steam. Flash steam can be used where steam at different pressures is wanted. It can be generated directly by discharging high-pressure condensate into a lower-pressure system, but most designers prefer to use a flash tank. Flashing is particularly attractive when it is too costly to return the high-pressure condensate to the boiler.

  • Assess end-use needs: Before upgrading a boiler system, evaluate the end uses. Boilers often provide hot water or steam at temperatures and pressures far beyond actual needs. Substantial energy savings can result from reducing the boiler's operating pressure or reducing the temperature of the fluid in the pipes.

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