Understanding Torque for Quarter-Turn Valves

Valve producers publish torques for their products so that actuation and mounting hardware may be correctly selected. However, printed torque values typically symbolize solely the seating or unseating torque for a valve at its rated stress. While these are important values for reference, published valve torques do not account for actual set up and operating traits. In order to determine the precise operating torque for valves, it is needed to grasp the parameters of the piping methods into which they are installed. Factors such as set up orientation, course of circulate and fluid velocity of the media all impression the precise working torque of valves.
Trunnion mounted ball valve operated by a single acting spring return actuator. Photo credit: Val-Matic
The American Water Works Association (AWWA) publishes detailed information on calculating working torques for quarter-turn valves. This data seems in AWWA Manual M49 Quarter-Turn Valves: Head Loss, Torque, and Cavitation Analysis. Originally revealed in 2001 with torque calculations for butterfly valves, AWWA M49 is presently in its third edition. In addition to info on butterfly valves, the current edition additionally includes working torque calculations for other quarter-turn valves including plug valves and ball valves. Overall, this guide identifies 10 components of torque that can contribute to a quarter-turn valve’s operating torque.
The first AWWA quarter-turn valve standard for 3-in. via 72-in. butterfly valves, C504, was revealed in 1958 with 25, 50 and 125 psi strain courses. In 1966 the 50 and 125 psi strain lessons had been increased to seventy five and one hundred fifty psi. The 250 psi strain class was added in 2000. The 78-in. and bigger butterfly valve standard, C516, was first published in 2010 with 25, 50, seventy five and a hundred and fifty psi pressure classes with the 250 psi class added in 2014. The high-performance butterfly valve commonplace was published in 2018 and contains 275 and 500 psi pressure courses as nicely as pushing the fluid move velocities above class B (16 ft per second) to class C (24 ft per second) and sophistication D (35 feet per second).
The first AWWA quarter-turn ball valve normal, C507, for 6-in. through 48-in. ball valves in 150, 250 and 300 psi stress courses was printed in 1973. In 2011, size range was increased to 6-in. by way of 60-in. These valves have always been designed for 35 ft per second (fps) most fluid velocity. The velocity designation of “D” was added in 2018.
Although the Manufacturers Standardization Society (MSS) first issued a product standard for resilient-seated cast-iron eccentric plug valves in 1991, the first a AWWA quarter-turn valve standard, C517, was not revealed until 2005. The 2005 dimension range was three in. via seventy two in. with a 175
Example butterfly valve differential pressure (top) and circulate price control home windows (bottom)
strain class for 3-in. through 12-in. sizes and one hundred fifty psi for the 14-in. via 72-in. The later editions (2009 and 2016) have not elevated the valve sizes or strain courses. The addition of the A velocity designation (8 fps) was added in the 2017 edition. This valve is primarily utilized in wastewater service the place pressures and fluid velocities are maintained at lower values.
The need for a rotary cone valve was acknowledged in 2018 and the AWWA Rotary Cone Valves, 6 Inch Through 60 Inch (150 mm via 1,500 mm), C522, is beneath improvement. This standard will encompass the identical one hundred fifty, 250 and 300 psi stress classes and the identical fluid velocity designation of “D” (maximum 35 toes per second) as the current C507 ball valve commonplace.
In basic, all the valve sizes, move charges and pressures have increased for the reason that AWWA standard’s inception.
AWWA Manual M49 identifies 10 components that have an result on operating torque for quarter-turn valves. These components fall into two basic categories: (1) passive or friction-based elements, and (2) active or dynamically generated elements. Because valve manufacturers cannot know the actual piping system parameters when publishing torque values, revealed torques are generally limited to the five elements of passive or friction-based components. These embody:
Passive torque elements:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The other 5 parts are impacted by system parameters corresponding to valve orientation, media and circulate velocity. The parts that make up lively torque embody:
Active torque elements:
Disc weight and center of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When considering all these various lively torque components, it is possible for the actual operating torque to exceed the valve manufacturer’s revealed torque values.
Although quarter-turn valves have been used within the waterworks business for a century, they’re being exposed to larger service stress and flow price service conditions. Since the quarter-turn valve’s closure member is always situated within the flowing fluid, these larger service circumstances immediately impression the valve. Operation of these valves require an actuator to rotate and/or maintain the closure member within the valve’s physique as it reacts to all the fluid pressures and fluid move dynamic conditions.
In addition to the increased service circumstances, the valve sizes are additionally growing. The dynamic conditions of the flowing fluid have higher effect on the larger valve sizes. Therefore, the fluid dynamic effects become more necessary than static differential stress and friction hundreds. Valves may be leak and hydrostatically shell tested during fabrication. However, the total fluid move situations cannot be replicated before site set up.
Because of the development for increased valve sizes and elevated working situations, it’s increasingly necessary for the system designer, operator and owner of quarter-turn valves to better understand the impression of system and fluid dynamics have on valve choice, development and use.
The AWWA Manual of Standard Practice M forty nine is dedicated to the understanding of quarter-turn valves together with working torque requirements, differential stress, flow situations, throttling, cavitation and system installation variations that directly influence the operation and successful use of quarter-turn valves in waterworks systems.
The fourth edition of M49 is being developed to include the changes within the quarter-turn valve product requirements and installed system interactions. A new chapter might be devoted to strategies of control valve sizing for fluid move, strain control and throttling in waterworks service. This methodology contains explanations on using pressure, flow price and cavitation graphical home windows to offer the user a thorough picture of valve performance over a spread of anticipated system operating conditions.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton began his career as a consulting engineer in the waterworks trade in Chicago. He joined Val-Matic in 2011 and was appointed president of Val-Matic in May 2021, following the retirement of John Ballun. Dalton previously worked at Val-Matic as Director of Engineering. He has participated in requirements creating organizations, together with AWWA, MSS, ASSE and API. Dalton holds BS and MS levels in Civil and Environmental Engineering together with Professional Engineering Registration.
John Holstrom has been involved in quarter-turn valve and actuator engineering and design for 50 years and has been an lively member of each the American Society of Mechanical Engineers (ASME) and the American Water Works Association (AWWA) for greater than 50 years. He is the chairperson of the AWWA sub-committee on the Manual of Standard Practice, M49, “Quarter-Turn Valves: Head Loss, Torque and Cavitation Analysis.” He has also labored with the Electric Power Research Institute (EPRI) within the growth of their quarter-turn valve efficiency prediction strategies for the nuclear energy business.

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