Understanding Torque for Quarter-Turn Valves

Valve manufacturers publish torques for their merchandise so that actuation and mounting hardware can be correctly chosen. However, printed torque values often symbolize solely the seating or unseating torque for a valve at its rated strain. While these are important values for reference, printed valve torques do not account for precise installation and working characteristics. In order to find out the actual working torque for valves, it’s necessary to know the parameters of the piping systems into which they’re put in. Factors corresponding to set up orientation, direction 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 info appears 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 currently in its third version. In addition to information on butterfly valves, the present edition additionally consists of operating torque calculations for different quarter-turn valves together with plug valves and ball valves. Overall, this handbook identifies 10 parts of torque that may contribute to a quarter-turn valve’s working torque.
Example torque calculation abstract graph
The first AWWA quarter-turn valve standard for 3-in. via 72-in. butterfly valves, C504, was printed in 1958 with 25, 50 and one hundred twenty five psi strain classes. In 1966 the 50 and a hundred twenty five psi pressure lessons have been elevated to seventy five and 150 psi. The 250 psi strain class was added in 2000. The 78-in. and larger butterfly valve normal, C516, was first printed in 2010 with 25, 50, seventy five and one hundred fifty psi pressure classes with the 250 psi class added in 2014. The high-performance butterfly valve normal was published in 2018 and contains 275 and 500 psi pressure courses in addition to pushing the fluid flow velocities above class B (16 ft per second) to class C (24 feet per second) and sophistication D (35 feet per second).
The first AWWA quarter-turn ball valve normal, C507, for 6-in. by way of 48-in. ball valves in one hundred fifty, 250 and 300 psi strain courses was printed in 1973. In 2011, measurement vary was elevated to 6-in. via 60-in. These valves have always been designed for 35 ft per second (fps) maximum fluid velocity. เกจวัดน้ำยาแอร์refco 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 commonplace, C517, was not revealed till 2005. The 2005 dimension range was three in. by way of 72 in. with a 175
Example butterfly valve differential strain (top) and move fee control windows (bottom)
pressure 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) haven’t increased the valve sizes or stress classes. The addition of the A velocity designation (8 fps) was added within 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 recognized in 2018 and the AWWA Rotary Cone Valves, 6 Inch Through 60 Inch (150 mm via 1,500 mm), C522, is underneath development. This standard will encompass the same one hundred fifty, 250 and 300 psi pressure lessons and the identical fluid velocity designation of “D” (maximum 35 ft per second) as the present C507 ball valve normal.
In basic, all of the valve sizes, move charges and pressures have elevated because the AWWA standard’s inception.
AWWA Manual M49 identifies 10 parts that have an effect on working torque for quarter-turn valves. These parts fall into two basic categories: (1) passive or friction-based components, and (2) lively or dynamically generated components. Because valve producers cannot know the actual piping system parameters when publishing torque values, revealed torques are generally restricted to the five elements of passive or friction-based parts. These embody:
Passive torque components:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The other five components are impacted by system parameters corresponding to valve orientation, media and move velocity. The components that make up lively torque include:
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 varied active torque components, it is attainable for the actual operating torque to exceed the valve manufacturer’s published torque values.
Although quarter-turn valves have been used within the waterworks industry for a century, they are being uncovered to higher service strain and move price service circumstances. Since the quarter-turn valve’s closure member is all the time positioned within the flowing fluid, these greater service circumstances instantly impact the valve. Operation of those valves require an actuator to rotate and/or maintain the closure member throughout the valve’s physique as it reacts to all of the fluid pressures and fluid flow dynamic circumstances.
In addition to the increased service situations, the valve sizes are additionally rising. The dynamic conditions of the flowing fluid have higher effect on the bigger valve sizes. Therefore, the fluid dynamic effects turn into extra essential than static differential pressure and friction masses. Valves can be leak and hydrostatically shell tested during fabrication. However, the complete fluid flow conditions can’t be replicated earlier than web site installation.
Because of the development for elevated valve sizes and increased operating conditions, it’s increasingly necessary for the system designer, operator and proprietor of quarter-turn valves to raised perceive the impression of system and fluid dynamics have on valve selection, construction and use.
The AWWA Manual of Standard Practice M 49 is dedicated to the understanding of quarter-turn valves including working torque necessities, differential stress, move conditions, throttling, cavitation and system set up differences that directly influence the operation and profitable use of quarter-turn valves in waterworks techniques.
The fourth version of M49 is being developed to include the modifications within the quarter-turn valve product standards and installed system interactions. A new chapter will be dedicated to methods of management valve sizing for fluid flow, stress control and throttling in waterworks service. This methodology consists of explanations on using stress, move rate and cavitation graphical home windows to supply the person a thorough image of valve performance over a variety of anticipated system working circumstances.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton began his career as a consulting engineer within the waterworks business 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 standards creating organizations, together with AWWA, MSS, ASSE and API. Dalton holds BS and MS degrees 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 energetic 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 improvement of their quarter-turn valve efficiency prediction methods for the nuclear power trade.

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