# Butterfly Valves - Torque, Head Loss, and Cavitation

This guide offers assistance for utilizing the flexible butterfly valve in waterworks carrier. assurance comprises strategies for calculating working torque, head loss, and cavitation. additionally integrated are prompt tools for selecting actuator sizes, warding off valve failure because of inner forces produced through water movement and strain, lowering noise, and fighting harmful vibrations.

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Extra resources for Butterfly Valves - Torque, Head Loss, and Cavitation Analysis

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Similarly, hydrostatic force (discussed in chapter 2) will open an unsecured valve with a horizontal shaft in a horizontal line with water on one side of the disc. Throttling Flow Butterfly valves have good flow characteristics and are often used for throttling flow. However, rubber-seated butterfly valves are usually limited to a throttling range of 20" to 70". Operating valves at positions less than 20" open may cause high localized velocities and cavitation, which can damage the seating surfaces.

28 Where: P, = Pu = reference upstream pressure, psig (kPa) vapor pressure adjusted for temperature and atmospheric pressure, psig (kPa) Put = upstream pressure from test, psig (kPa) Put = vapor pressure from test, psig (kPa) Alternative equations may be used to present and predict cavitation data. 9. Summarize the test data for each data point and report at least these results: Copyright (C) 2001 American Water Works Association All Rights Reserved VALVE TESTING 37 Valve model and materials Construction drawing and revision level or date Valve angle, in degrees open Flow velocity (based on nominal valve size) Total head loss (measured) 0 Head loss (piping) Net head loss (valve only) Average K,e value Opening and closing torque (consisting of Td + Tb + T,) TP Tb Td ct Cf q ,o,, or other cavitation coefficients at the reference pressure SEATING TORQUE TEST PROCEDURE The following steps represent a generic procedure for performing a seat torque test for a rubber-seated butterfly valve.

Copyright (C) 2001 American Water Works Association All Rights Reserved Index Terms Links O Offset discs 7 and dynamic torque Orientation of the valve 7f. 15f. 8 8f. 13 13f. 5 6f. P Packing and hub torque Pipe diameter and flow and pressure direction 41 free inlet or discharge 42 43f. upstream elbows or branch tees 41 42f. and upstream valves 41 42f. Pressure differential 16 R Reservoir inlet installations 3 3f. Rubber seats 1 3 designs 6 42 43f. S Seat-side flow orientation 8f. Seating torque 12 test procedure 12f.