Minimum flow line of the pump
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Dear teachers: In accordance with Article 11.6 of the \"Code for Design of Process Piping in Refining Units\" (SH/T 3122-2013), if the flow rate of the medium to be transported by the centrifugal pump might be lower than its minimum flow rate, a minimum flow line should be installed. A flow-limiting orifice plate, globe valve, or control valve should be installed on the minimum flow line. The statement that a flow-limiting orifice plate, stop valve, or control valve should be installed on the minimum flow line means that a combination of a flow-limiting orifice plate and a stop valve should be used ； Or a control valve. Still, a flow-limiting orifice plate must be installed, along with a shut-off valve or control valve.
It means either installing a combination of a flow control orifice plate and a shut-off valve, or installing only a control valve. It’s not that a flow-limiting orifice plate must be installed. .
I remember that old pumps only had stop valves, no flow control orifice plates
A flow control orifice plate, or simply a control valve, will suffice.