Valves high pressure side vent

High pressure side vent valve. This allows the panel upstream from the regulator to be directly vented. Before opening the high pressure vent valve, it is extremely important for the cylinder valve to be closed. 

If the high side is being tested, the low side should be vented to the atmosphere, in case there is any leakage between them which could bring excessive pressure onto the low side. It may be necessary to remove relief valves. Other valves within the circuit will have to be open or closed as necessary to obtain the test pressure. Servo-operated valves will not open on a dead circuit, and must be opened mechanically. 

Open the high point vent on the top of the channel head. I am assuming water is on the tube side of a horizontal shell and tube exchanger. If the exchanger is elevated by 30 or 50 ft, there may be no water pressure at this elevation. If so, temporarily close the cooling water outlet gate valve part way to push the water out of the vent. Now take the gas test meter (the one used by the operators to issue entry permits to vessels) and hold the sample probe above the water stream to test for hydrocarbons. 

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