Shut off valve - precautions for operation of pneumatic shut off valve
Time: 2020-09-21 12:46:20 Source: Yonglong Valve Reading: zero second
Shut off valve - precautions for operation of pneumatic shut off valve
As for the selection of safety protection gas on and gas off shut-off valves, generally speaking, it is considered from the perspective of safety. In the storage tank and production process of combustible media, it is better to select gas on shut-off valves to protect these equipment, that is, in case of power failure/power failure or insufficient gas source pressure, the valves are closed. Therefore, in each operating system of the chemical plant, the normally open and normally closed shut-off valves are very important in production operation, which directly affects safety production and personal safety of workers.
There are two types of pneumatic cut-off valves: air on (when there is signal pressure, the valve is open) and air off (when there is signal pressure, the valve is closed). The air on and air off of the cut-off valve are mainly determined according to the safety requirements of the process unit. The general principle is that when the gas source of the emergency cut-off valve is interrupted, the raw materials and heat sources entering the device and equipment should be cut off, and the output of products outside the device should be stopped, the gas opening cut-off valve should be used. For the liquid level extraction shut-off valve of tower and vessel, the air opening shut-off valve shall also be selected. If the cut-off valve for storage tank and vessel pressure is installed at the output port, the gas off cut-off valve shall be selected, and the cut-off valve at the input end of the storage tank shall be the gas off cut-off valve.
Before the unit is started, the test of pneumatic shut-off valve shall be carried out. During the test, special personnel shall be assigned to monitor the action of shut-off valve and baffle locally, check that the connecting rod and pin of the actuator shall be free from looseness, bending and falling off, check that the DCS opening indication shall be consistent with the local indication, whether the switch direction is correct, and the action is flexible. Interlocking test shall be carried out with relevant disciplines for those with interlocking circuits, The pneumatic switch device for test shall be flexible and free from air leakage and abnormalities. In case of any abnormality during the test, the test shall be stopped and the maintenance personnel shall be notified in time for handling. If internal leakage is found in the production process of the pneumatic cut-off valve, the manual valve at both ends shall be closed for timely maintenance or replacement.
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