A steam-piping system installed at a facility years ago may continue to serve buildings or spaces that are no longer in use. The steam continues to pressurize the piping to these areas. Steam also continues to condense on the pipe surface and be drained from the pipe by steam traps. This may not seem like a lot of waste. However, if the losses occur all day every day, the annual loss can be significant. Add the steam leaking from valves, fittings, and equipment in the unused branch lines, and the energy wasted escalates still further.
The solution to this situation is to isolate inactive portions of the steam-distribution system so that steam is not delivered to those lines. If no isolation valves are already installed, it would be advantageous to do so.
An analogous situation may occur on a daily basis. Some parts of a facility need steam for specific operations: dishwashers and steam kettles in a kitchen, clothes washers in the laundry, or sterilization equipment in a laboratory. Each of these may require steam for only 2 hours every day, while the rest of the building needs it, if only intermittently, for 24 hours a day. Automatic valves on the lines serving these functions can keep them from being a drain on the system for the better part of each day. This kind of control scheme is most cost-effective when the branch system is extensive, and the thermal losses are high. If existing steam valves need to be replaced, then electronic valves should be considered.
An inexpensive electronic timer can monitor the valve(s) initially, until they can be incorporated into a full energy-management system.
This same rationale applies to hot-water distribution loops, although to a lesser degree since the lower fluid distribution temperature means less thermal loss from leaks than with steam. Nevertheless, if the valve to a branch in occasional use is there—and if it can be easily controlled—it’s probably worthwhile to do so because of the energy saved. Even if some scheduling of equipment operation (e.g., having to wash clothes or dishes in a 2-hour window each day) incurs some inconvenience, the energy savings make it worth the trouble.
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Excerpt from Energy Conservation Projects.