Understanding Torque for Quarter-Turn Valves

Valve producers publish torques for their merchandise so that actuation and mounting hardware may be correctly selected. However, printed torque values often represent only the seating or unseating torque for a valve at its rated stress. While these are important values for reference, printed valve torques do not account for actual set up and operating characteristics. In order to find out the actual operating torque for valves, it’s needed to know the parameters of the piping techniques into which they’re put in. Factors such as installation orientation, path of move and fluid velocity of the media all impact the actual working 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 information on calculating working torques for quarter-turn valves. This data 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 at present in its third edition. In addition to data on butterfly valves, the current version additionally includes operating torque calculations for different quarter-turn valves together with plug valves and ball valves. Overall, this guide identifies 10 parts of torque that may contribute to a quarter-turn valve’s operating torque.
Example torque calculation summary graph
The first AWWA quarter-turn valve standard for 3-in. through 72-in. butterfly valves, C504, was published in 1958 with 25, 50 and one hundred twenty five psi stress courses. In 1966 the 50 and one hundred twenty five psi pressure lessons were increased to seventy five and one hundred fifty psi. The 250 psi pressure class was added in 2000. The 78-in. and larger butterfly valve normal, C516, was first revealed in 2010 with 25, 50, 75 and 150 psi stress lessons with the 250 psi class added in 2014. เกจวัดแรงดันคือ -performance butterfly valve normal was printed in 2018 and consists of 275 and 500 psi pressure courses in addition to pushing the fluid circulate velocities above class B (16 toes per second) to class C (24 feet per second) and class D (35 toes 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 strain classes was printed in 1973. In 2011, measurement range was elevated to 6-in. through 60-in. These valves 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 normal for resilient-seated cast-iron eccentric plug valves in 1991, the first a AWWA quarter-turn valve commonplace, C517, was not published until 2005. The 2005 measurement range was three in. through seventy two in. with a a hundred seventy five
Example butterfly valve differential stress (top) and circulate fee management windows (bottom)
pressure class for 3-in. via 12-in. sizes and a hundred and fifty psi for the 14-in. by way of 72-in. The later editions (2009 and 2016) haven’t elevated the valve sizes or stress lessons. The addition of the A velocity designation (8 fps) was added in the 2017 edition. This valve is primarily used in wastewater service where 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 under growth. This standard will embody the same 150, 250 and 300 psi pressure lessons and the same fluid velocity designation of “D” (maximum 35 toes per second) as the current C507 ball valve commonplace.
In general, 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 effect on working torque for quarter-turn valves. These components fall into two basic categories: (1) passive or friction-based parts, and (2) energetic or dynamically generated elements. Because valve producers can’t know the actual piping system parameters when publishing torque values, printed torques are generally limited to the 5 elements of passive or friction-based components. These embody:
Passive torque components:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The other 5 elements are impacted by system parameters such as valve orientation, media and circulate velocity. The components that make up lively torque include:
Active torque parts:
Disc weight and middle of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When contemplating all these varied active torque elements, it is potential for the actual operating torque to exceed the valve manufacturer’s published torque values.
Although quarter-turn valves have been used in the waterworks industry for a century, they are being exposed to larger service stress and flow rate service situations. Since the quarter-turn valve’s closure member is at all times situated in the flowing fluid, these higher service circumstances immediately 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 move dynamic circumstances.
In addition to the increased service circumstances, the valve sizes are additionally rising. The dynamic circumstances of the flowing fluid have higher effect on the larger valve sizes. Therefore, the fluid dynamic effects become extra essential than static differential pressure and friction hundreds. Valves may be leak and hydrostatically shell tested throughout fabrication. However, the total fluid move situations can’t be replicated before site installation.
Because of the development for increased valve sizes and increased working circumstances, it is increasingly important 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 49 is devoted to the understanding of quarter-turn valves together with working torque requirements, differential pressure, move situations, throttling, cavitation and system set up differences that directly affect the operation and successful use of quarter-turn valves in waterworks systems.
The fourth version of M49 is being developed to include the changes in the quarter-turn valve product standards and installed system interactions. A new chapter will be dedicated to methods of control valve sizing for fluid circulate, pressure control and throttling in waterworks service. This methodology contains explanations on the utilization of stress, circulate price and cavitation graphical home windows to provide the user a thorough image of valve performance over a spread of anticipated system operating circumstances.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton began his profession as a consulting engineer in the waterworks industry 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 standards creating 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 involved in quarter-turn valve and actuator engineering and design for 50 years and has been an active 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 additionally labored with the Electric Power Research Institute (EPRI) in the development of their quarter-turn valve efficiency prediction methods for the nuclear energy trade.

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