Standard Piping Procedures, Valves


Inlet shutoff valves Discharge shutoff valves
Inlet shutoff valves should be installed whenever supply steam cannot be shut off for trap maintenance. Steam main drips and large water heaters are examples of such applications. Discharge shutoff valves should be installed when the trap has a by-pass and/or when the trap discharges into a high-pressure return.

Check valves
Check valves are a must if no discharge line shutoff valve is used in the steam system. Some inverted bucket traps are available with internal check valves, while disc traps act as their own check valve. Check valves are always open in the normal direction of flow and close automatically when the flow is reversed. They may be placed in the inlet or discharge line of the trap. Check valves should be located at the inlet, or provided internally for inverted bucket traps when they are located above the drip point or subject to sudden pressure drops. Check valves should be provided in the discharge lines near the trap when a test valve is used, when the trap discharges into a high-pressure return, or if a discharge shutoff valve is not used.
Test valves
Test valves should be installed at the trap discharge and open to atmosphere. They provide an excellent means of visually testing the steam trap. This is the most highly recommended test method. There are three common procedures for installing test valves.
  • Install a plug valve that opens to atmosphere on the auxiliary outlet at the top of IB traps that are so equipped.
  • Install a three-way test valve downstream of small traps that can be serviced by the 1/2-inch (15 DN) to 3/4-inch (20 DN) valves available.
  • Install a tee with a plug valve opening to atmosphere downstream of other traps.
  • A shutoff or check valve should be located downstream of the test valve, if necessary, to isolate the trap from the return line during testing.




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