Predicting pressure losses in straight-through diaphragm valves

Abstract

The diaphragm valve traces its origins to ancient Roman and Greek times, where it was used to control water flow and temperature of hot baths (Century-Instruments, 2007). The particularity of this type of valve is the presence of a diaphragm or membrane which controls the flow. Over the years, the design of this type of valve has evolved into two major varieties. The first is the "weir" type, more suitable for less viscous fluids and a second is the "straight-through" type, suitable for suspensions. This study is focused on the straight-through. With the widespread use of such valves in the mining and mineral processing operations and other industrial applications, although there has been improvement in the selection of the diaphragms and body materials of the valves, as well as actuation methods, improvements were not accompanied by thorough hydraulic investigation to determine the method of calculating the additional head loss caused by the presence of diaphragm valves in pipelines, and in particular for the laminar flow of non-Newtonian fluids. The limited correlations available, such as Hooper's (1981), Perry's (1997) and Miller's (1990) are valid only for Newtonian fluids. Furthermore they are classified as Class 3 (Miller, 1990) which means they are not corroborated in other independent studies. BM