The pump inlet pressure control valve should be a pneumatic open valve; what is the reason for choosing a pneumatic close valve for the outlet?
Thread Content
From a safety perspective, why should a pneumatic open valve be used for the pump inlet pressure control valve, while a pneumatic close valve should be used for the outlet pressure control valve?
A gas open valve controls the pump inlet pressure by regulating the gas flow, while a gas close valve can limit the pump outlet pressure to ensure the safe operation of the system. -
Choosing between air-open and air-close is determined by what state the valve should be in under abnormal operating conditions to ensure safety； For example: in the case of steam control valves, when abnormal operating conditions occur and the steam supply must be stopped, a valve that operates in response to air pressure should be selected for such applications ； When under abnormal operating conditions, steam must be supplied; in such cases, a gas-operated valve should be selected for the control valve ；
Since air-open valves can adjust the system pressure in real time, the flow rate can be reduced when it is necessary to lower the pressure; whereas air-close valves can effectively limit the outlet pressure of the pump, thereby preventing overpressure conditions. This ensures the safe operation of the system. -
For the pump outlet pressure control valve, it is generally not advisable to use an FO valve alone, to prevent the motor from being overloaded and damaged. If the safety analysis of the downstream system requires that the flow of material pumped by this pump must not be interrupted in the event of a failure in the instrument air supply (for example, when the material being transported is a coolant used for heat removal in a reaction system), then a combination of an FO valve and a flow restriction orifice plate should be used as the pressure control valve at the pump outlet.