Understanding Torque for Quarter-Turn Valves

Valve manufacturers publish torques for his or her merchandise in order that actuation and mounting hardware can be correctly selected. However, revealed torque values often symbolize only the seating or unseating torque for a valve at its rated stress. While these are necessary values for reference, revealed valve torques don’t account for precise installation and working traits. In order to determine the precise working torque for valves, it’s necessary to grasp the parameters of the piping methods into which they’re put in. Factors such as set up orientation, direction of flow and fluid velocity of the media all influence the actual working torque of valves.
Trunnion mounted ball valve operated by a single appearing spring return actuator. Photo credit: Val-Matic
The American Water Works Association (AWWA) publishes detailed data on calculating operating torques for quarter-turn valves. This information appears in AWWA Manual M49 Quarter-Turn Valves: Head Loss, Torque, and Cavitation Analysis. Originally published in 2001 with torque calculations for butterfly valves, AWWA M49 is currently in its third version. In Special to information on butterfly valves, the current edition also contains working torque calculations for other quarter-turn valves including plug valves and ball valves. Overall, this handbook identifies 10 components of torque that may contribute to a quarter-turn valve’s operating torque.
Example torque calculation abstract graph
The first AWWA quarter-turn valve normal for 3-in. through 72-in. butterfly valves, C504, was revealed in 1958 with 25, 50 and a hundred twenty five psi stress classes. In 1966 the 50 and 125 psi pressure lessons had been elevated to 75 and one hundred fifty psi. The 250 psi pressure class was added in 2000. The 78-in. and bigger butterfly valve commonplace, C516, was first printed in 2010 with 25, 50, 75 and 150 psi strain courses with the 250 psi class added in 2014. The high-performance butterfly valve commonplace was printed in 2018 and consists of 275 and 500 psi pressure lessons in addition to pushing the fluid move velocities above class B (16 toes per second) to class C (24 feet per second) and sophistication D (35 toes per second).
The first AWWA quarter-turn ball valve standard, C507, for 6-in. via 48-in. ball valves in one hundred fifty, 250 and 300 psi stress classes was printed in 1973. In 2011, dimension vary was elevated to 6-in. via 60-in. These valves have always been designed for 35 ft per second (fps) maximum 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 primary a AWWA quarter-turn valve normal, C517, was not printed till 2005. The 2005 dimension vary was three in. by way of 72 in. with a a hundred seventy five
Example butterfly valve differential strain (top) and move fee control home windows (bottom)
stress class for 3-in. by way of 12-in. sizes and 150 psi for the 14-in. through 72-in. The later editions (2009 and 2016) haven’t increased the valve sizes or strain classes. The addition of the A velocity designation (8 fps) was added in the 2017 version. This valve is primarily utilized in wastewater service the place pressures and fluid velocities are maintained at decrease values.
The want for a rotary cone valve was acknowledged in 2018 and the AWWA Rotary Cone Valves, 6 Inch Through 60 Inch (150 mm by way of 1,500 mm), C522, is beneath improvement. This standard will embody the same 150, 250 and 300 psi strain classes and the same fluid velocity designation of “D” (maximum 35 toes per second) as the current C507 ball valve commonplace.
In common, all the valve sizes, move charges and pressures have increased for the reason that AWWA standard’s inception.
AWWA Manual M49 identifies 10 elements that affect operating torque for quarter-turn valves. These elements fall into two common categories: (1) passive or friction-based components, and (2) energetic or dynamically generated parts. Because valve manufacturers cannot know the actual piping system parameters when publishing torque values, printed torques are generally restricted to the five components of passive or friction-based components. These embrace:
Passive torque elements:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The different 5 elements are impacted by system parameters similar to valve orientation, media and move velocity. The components that make up active torque embrace:
Active torque elements:
Disc weight and center of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When contemplating all these varied active torque parts, it’s possible for the precise working 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’re being exposed to greater service strain and circulate price service conditions. Since the quarter-turn valve’s closure member is at all times positioned within the flowing fluid, these greater service situations immediately influence the valve. Operation of these valves require an actuator to rotate and/or hold the closure member throughout the valve’s physique as it reacts to all the fluid pressures and fluid flow dynamic conditions.
In addition to the increased service conditions, the valve sizes are also increasing. The dynamic circumstances of the flowing fluid have higher effect on the bigger valve sizes. Therefore, the fluid dynamic effects turn into extra important than static differential pressure and friction hundreds. Valves could be leak and hydrostatically shell tested throughout fabrication. However, the full fluid flow circumstances cannot be replicated earlier than web site installation.
Because of the development for increased valve sizes and increased working conditions, it is increasingly important for the system designer, operator and owner of quarter-turn valves to higher understand the influence of system and fluid dynamics have on valve choice, building and use.
The AWWA Manual of Standard Practice M 49 is devoted to the understanding of quarter-turn valves including operating torque requirements, differential strain, flow circumstances, throttling, cavitation and system installation differences that immediately influence the operation and profitable use of quarter-turn valves in waterworks techniques.
The fourth version of M49 is being developed to incorporate the changes within the quarter-turn valve product requirements and put in system interactions. A new chapter might be dedicated to strategies of control valve sizing for fluid move, pressure management and throttling in waterworks service. This methodology contains explanations on the usage of pressure, move price and cavitation graphical windows to offer the user a thorough image of valve efficiency over a spread of anticipated system working situations.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton started his career as a consulting engineer within 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 beforehand worked at Val-Matic as Director of Engineering. He has participated in requirements creating organizations, including AWWA, MSS, ASSE and API. Dalton holds BS and MS levels in Civil and Environmental Engineering along with Professional Engineering Registration.
John Holstrom has been concerned in quarter-turn valve and actuator engineering and design for 50 years and has been an lively member of both 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 additionally worked with the Electric Power Research Institute (EPRI) within the development of their quarter-turn valve efficiency prediction strategies for the nuclear energy trade.

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