Throttle orifice plates and orifice plate flow meters in the basic pump unit mode

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This is the symbol for a orifice flow meter. 3.0.3.4 When measuring or regulating the flow rate of liquefied gas materials, the pressure drop must be taken into account, so that the pressure downstream of the flow meter is greater than the saturated vapor pressure at that temperature. To this end, a flow measurement orifice plate is usually installed upstream of the control valve, while the control valve is placed as close as possible to the liquid-receiving equipment downstream of the pump, as shown in the figure. My understanding is that a pressure drop downstream of the orifice flow meter, or uneven pressure distribution, may cause the material to flash. The farther the control valve is from the orifice flow meter, the more stable the measured pressure will be. 4.0.1.2 (2) If it is expected that the pump will operate in the short term at a flow rate of less than 20% of its rated flow rate, a bypass equipped with a flow-limiting orifice plate should be installed, without any valves. The size of the orifice plate should be such that the flow rate through the pump is at least 20% of the pump’s rated flow rate. When flashing may occur as the liquid passes through the bypass orifice plate, other low-flow protection measures should be taken. My understanding is that, due to the characteristics of the flow restriction orifice plate, the pressure drop behind the orifice plate may lead to flashing.