Cavitation in a Precision Turbine Flowmeter (PTF) will take place when the local pressures fall close to or below the vapor pressure of the liquid product. The formation of bubbles and their collapse or local vaporization of product as it passes over the rotor blade surface can cause erratic behavior in the PRECISION TURBINE FLOWMETER.
Maintaining a system backpressure of 2 times the PTF pressure drop plus 1.25 times the product vapor pressure is sufficient to prevent cavitation as shown by the following formula:
BP= (P x 2) + (VP x 1.25)
BP= Required back pressure
P= Pressure drop at maximum flow
VP= Absolute vapor pressure at maximum temperature
Cavitation usually causes the rotor to speed up at the high flow rate due to the increased flow volume and causes the accuracy curve of the PRECISION TURBINE FLOWMETER to be adversely affected. Sustained over-speeding of the rotor can lead to damage to the meter.