Positive displacement flowmeters rely on the fluid to push the measuring fittings, so the pressure loss is high. The pressure loss of a positive displacement flowmeter is larger than that of other types of flowmeters of the same diameter and flow. The pressure loss of general liquids is 20 to 100 kPa. When measuring liquids with high vapor pressure, excessive pressure drop will cause cavitation. If cavitation exists for a long time, it will damage the flowmeter accessories. Some flowmeters that allow short-term overflow to 120% of the upper limit of measurement should pay more attention to this problem . Extended reading: Orifice Plate Flow Meter