Batley Butterfly Valves - Weir Power & Industrial - #28

Text version of the page

28 Weir Power & Industrial First choice for power and industrial protection Batley Valve BV 6-0810 VARIDIFF VANE BV30000 Description The Batley Varidiff trim was developed in the early 1970’s in response to an increased demand for a low cost solution to the problems of cavitation and noise generated by conventional butterfly valves due to their inherent high pressure recovery. The Varidiff trim, see Figure 1 on page 29, which incorporates two hemi-spherical control elements on opposite sides of the vane and ends of the face of the vane, significantly reduces the pressure recovery particularly at low openings i.e. 0 to 30 degrees. In terms of the pressure recovery factor which is used to determine the pressure at the vena-contracta, a value of 0.9 is achieved at openings below 30 degrees compared with 0.7 for a standard vane. Figure 3 on page 30, gives a comparison between the static pressure recovery between a standard vane and a varidiff vane. Although the varidiff offers lower pressure recovery at openings up to 30 degrees it is sometimes necessary to complement the vane with an integral baffle either fitted into the valve body or optionally supplied loose. As the valve opens above 30 degrees the pressure drop is broken down across the vane and the baffle plate which results in a reduction in pressure recovery. The varidiff trim can be incorporated within both the swing through range and the Hyperseal range of valves. The flow characteristic is equal percentage with a turn down in excess of 100:1. Due to the low dynamic torque a stable mode of operation is maintained for openings between 5 and 80 degrees. Applications The Varidiff trim has been used successfully on a number of demanding applications where the use of standard butterfly valves had resulted in severe operational problems, and premature failure of the valve. One such application is back pressure control on overboard dump lines in the offshore industry. Other applications include firewater ring system control valve, brine blowdown control, jetty loading valves, sea-water drain and re-circulation, cooling water circulation, and distillate to culvert valves. In addition to the above liquid service applications it has also found use on steam vent headers, and gas pipelines, for low noise requirements. Flow direction