Cavitation indices for high pressure orifice plate energy dissipators

Abstract

A problem of providing a simple device for pressure dissipation in mine underground high pressure water reticulation systems was investigated; a required feature of this device was operation without cavitation. An orifice plate was selected, and various orifice diameter ratios (0.206–0.444) for a range of upstream pressures (2000–7000 kPa) were examined for their incipient cavitation points and flow/pressure drop behaviour. Experimental work was conducted in two parts, low pressure and high pressure; the low pressure part of the work was carried out at the University of the Witwatersrand and the high pressure part at the East Driefontein Gold Mine. Both sets of experiments yielded data that were inconsistent with previously predicted values of incipient cavitation under conditions of relatively low head (up to 137 m of water); analysis of the results yielded a new simple cavitation prediction method based on cavitation inception and orifice pressure drop data which is easily presented in graphical form. The results showed that upstream pressure affected the pressure drop required for incipient cavitation, for the same orifice size; and that the orifice ratio affected the pressure drop required for incipient cavitation, for the same upstream pressure.