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 usually symbolize solely the seating or unseating torque for a valve at its rated stress. While these are necessary values for reference, printed valve torques do not account for precise installation and working traits. In order to determine the precise working torque for valves, it’s needed to know the parameters of the piping methods into which they’re installed. Factors such as installation orientation, path of circulate and fluid velocity of the media all influence the precise operating torque of valves.
Trunnion mounted ball valve operated by a single performing spring return actuator. Photo credit score: Val-Matic
The American Water Works Association (AWWA) publishes detailed info on calculating operating torques for quarter-turn valves. This info 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 contains working torque calculations for other quarter-turn valves including plug valves and ball valves. Overall, this manual identifies 10 elements of torque that may contribute to a quarter-turn valve’s operating torque.
Example torque calculation summary graph
The first AWWA quarter-turn valve normal for 3-in. by way of 72-in. butterfly valves, C504, was printed in 1958 with 25, 50 and a hundred twenty five psi strain classes. In 1966 the 50 and one hundred twenty five psi stress courses were elevated to seventy five and a hundred and fifty psi. The 250 psi stress 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 150 psi stress lessons with the 250 psi class added in 2014. The high-performance butterfly valve standard was printed in 2018 and consists of 275 and 500 psi strain lessons in addition to pushing the fluid flow velocities above class B (16 ft per second) to class C (24 toes per second) and sophistication D (35 feet per second).
The first AWWA quarter-turn ball valve normal, C507, for 6-in. via 48-in. ball valves in a hundred and fifty, 250 and 300 psi pressure lessons was printed in 1973. In 2011, measurement range was increased to 6-in. via 60-in. Members only have at all times 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 first a AWWA quarter-turn valve standard, C517, was not printed till 2005. The 2005 measurement range was 3 in. through 72 in. with a one hundred seventy five
Example butterfly valve differential stress (top) and circulate fee management windows (bottom)
pressure class for 3-in. by way of 12-in. sizes and a hundred and fifty 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 edition. This valve is primarily used in wastewater service the place pressures and fluid velocities are maintained at lower 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 development. This commonplace will encompass the identical 150, 250 and 300 psi strain lessons and the same fluid velocity designation of “D” (maximum 35 toes per second) as the present C507 ball valve normal.
In basic, all of the valve sizes, flow rates and pressures have increased because the AWWA standard’s inception.
AWWA Manual M49 identifies 10 components that have an effect on working torque for quarter-turn valves. These components fall into two common categories: (1) passive or friction-based elements, and (2) lively or dynamically generated components. Because valve manufacturers can’t know the actual piping system parameters when publishing torque values, printed torques are typically limited to the 5 elements of passive or friction-based parts. These include:
Passive torque components:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The different five parts are impacted by system parameters corresponding to valve orientation, media and flow velocity. The parts that make up active torque embrace:
Active torque elements:
Disc weight and heart of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When contemplating all these various active torque components, it’s possible for the precise working 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 uncovered to higher service strain and flow fee service conditions. Since the quarter-turn valve’s closure member is all the time positioned within the flowing fluid, these greater service circumstances directly impression the valve. Operation of those valves require an actuator to rotate and/or hold the closure member throughout the valve’s body because it reacts to all of the fluid pressures and fluid move dynamic conditions.
In addition to the elevated service situations, the valve sizes are additionally rising. The dynamic conditions of the flowing fluid have higher impact on the bigger valve sizes. Therefore, the fluid dynamic results turn out to be more important than static differential strain and friction hundreds. Valves could be leak and hydrostatically shell tested during fabrication. However, the complete fluid move conditions can’t be replicated before website installation.
Because of the pattern for elevated valve sizes and elevated working conditions, it’s increasingly important for the system designer, operator and owner of quarter-turn valves to raised perceive the impression of system and fluid dynamics have on valve choice, building and use.
The AWWA Manual of Standard Practice M 49 is dedicated to the understanding of quarter-turn valves including operating torque necessities, differential strain, flow circumstances, throttling, cavitation and system installation differences that directly influence the operation and profitable use of quarter-turn valves in waterworks methods.
The fourth version of M49 is being developed to incorporate the modifications in the quarter-turn valve product standards and put in system interactions. A new chapter shall be devoted to methods of management valve sizing for fluid move, pressure management and throttling in waterworks service. This methodology consists of explanations on using stress, move fee and cavitation graphical windows to provide the consumer an intensive image of valve performance over a variety of anticipated system operating conditions.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton started his profession 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 beforehand labored at Val-Matic as Director of Engineering. He has participated in requirements growing organizations, including 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 concerned 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 more 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 labored with the Electric Power Research Institute (EPRI) in the development of their quarter-turn valve efficiency prediction methods for the nuclear energy industry.

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