Understanding Torque for Quarter-Turn Valves

Valve manufacturers publish torques for their merchandise so that actuation and mounting hardware can be properly chosen. However, revealed torque values usually symbolize only the seating or unseating torque for a valve at its rated pressure. While these are necessary values for reference, published valve torques don’t account for precise set up and operating characteristics. In order to determine the precise working torque for valves, it is necessary to understand the parameters of the piping methods into which they’re installed. Factors corresponding to set up orientation, direction of flow and fluid velocity of the media all influence the precise operating torque of valves.
Trunnion mounted ball valve operated by a single appearing spring return actuator. Photo credit score: Val-Matic
The American Water Works Association (AWWA) publishes detailed information on calculating operating 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 edition. In addition to info on butterfly valves, the present version also contains operating torque calculations for different quarter-turn valves together with plug valves and ball valves. Overall, this handbook identifies 10 components of torque that can contribute to a quarter-turn valve’s operating torque.
Example torque calculation summary graph
The first AWWA quarter-turn valve commonplace for 3-in. by way of 72-in. butterfly valves, C504, was printed in 1958 with 25, 50 and a hundred twenty five psi stress lessons. In 1966 the 50 and one hundred twenty five psi strain courses have been elevated to seventy five and a hundred and fifty psi. The 250 psi strain class was added in 2000. The 78-in. and bigger butterfly valve normal, C516, was first published 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 contains 275 and 500 psi strain lessons in addition to pushing the fluid move velocities above class B (16 feet per second) to class C (24 ft per second) and class D (35 ft per second).
The first AWWA quarter-turn ball valve commonplace, C507, for 6-in. through 48-in. ball valves in 150, 250 and 300 psi strain lessons was printed in 1973. In 2011, measurement vary was increased to 6-in. by way of 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 เกจวัดแรงดันลม10bar (MSS) first issued a product normal for resilient-seated cast-iron eccentric plug valves in 1991, the primary a AWWA quarter-turn valve commonplace, C517, was not revealed till 2005. The 2005 measurement vary was 3 in. by way of 72 in. with a 175
Example butterfly valve differential stress (top) and flow fee control home windows (bottom)
pressure class for 3-in. via 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 pressure classes. The addition of the A velocity designation (8 fps) was added within the 2017 version. This valve is primarily utilized in wastewater service where 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 under development. This commonplace will embody the same 150, 250 and 300 psi strain courses and the same fluid velocity designation of “D” (maximum 35 toes per second) as the present C507 ball valve normal.
In general, all of the valve sizes, move charges and pressures have elevated because the AWWA standard’s inception.
AWWA Manual M49 identifies 10 parts that affect operating torque for quarter-turn valves. These components fall into two common categories: (1) passive or friction-based elements, and (2) energetic or dynamically generated parts. Because valve manufacturers can not know the actual piping system parameters when publishing torque values, published torques are typically limited to the five components of passive or friction-based elements. These embrace:
Passive torque elements:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The different five components are impacted by system parameters such as valve orientation, media and move velocity. The parts that make up active torque embody:
Active torque parts:
Disc weight and heart of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When considering all these varied energetic torque parts, it’s attainable for the actual working torque to exceed the valve manufacturer’s printed torque values.
Although quarter-turn valves have been used within the waterworks industry for a century, they’re being exposed to larger service stress and circulate fee service circumstances. Since the quarter-turn valve’s closure member is always positioned in the flowing fluid, these larger service conditions directly impression the valve. Operation of these valves require an actuator to rotate and/or hold the closure member throughout the valve’s body as it reacts to all of the fluid pressures and fluid flow dynamic circumstances.
In addition to the elevated service circumstances, the valve sizes are additionally growing. The dynamic circumstances of the flowing fluid have greater impact on the bigger valve sizes. Therefore, the fluid dynamic effects turn into more essential than static differential stress and friction hundreds. Valves may be leak and hydrostatically shell examined during fabrication. However, the full fluid circulate conditions can’t be replicated earlier than site set up.
Because of the trend for elevated valve sizes and increased working circumstances, it is increasingly important for the system designer, operator and owner of quarter-turn valves to raised perceive the influence of system and fluid dynamics have on valve selection, building and use.
The AWWA Manual of Standard Practice M 49 is dedicated to the understanding of quarter-turn valves including working torque requirements, differential pressure, flow circumstances, throttling, cavitation and system installation differences that directly affect the operation and successful use of quarter-turn valves in waterworks methods.
The fourth version of M49 is being developed to include the changes within the quarter-turn valve product standards and put in system interactions. A new chapter shall be devoted to methods of control valve sizing for fluid move, strain management and throttling in waterworks service. This methodology includes explanations on the use of stress, move rate and cavitation graphical home windows to supply the person 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 began his career as a consulting engineer in 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 worked at Val-Matic as Director of Engineering. He has participated in standards developing organizations, including 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 concerned in quarter-turn valve and actuator engineering and design for 50 years and has been an active 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 growth of their quarter-turn valve efficiency prediction methods for the nuclear power industry.

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