Understanding Torque for Quarter-Turn Valves

Valve producers publish torques for their products in order that actuation and mounting hardware can be properly chosen. However, published torque values typically symbolize only the seating or unseating torque for a valve at its rated pressure. While these are important values for reference, printed valve torques don’t account for actual set up and working characteristics. In order to find out the precise operating torque for valves, it is necessary to know the parameters of the piping techniques into which they’re put in. Factors similar to set up orientation, course of flow and fluid velocity of the media all impact 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 info on calculating operating torques for quarter-turn valves. This data seems 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 version. In addition to information on butterfly valves, the current version also consists of operating torque calculations for different quarter-turn valves including plug valves and ball valves. Overall, this handbook identifies 10 parts of torque that can contribute to a quarter-turn valve’s working 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 a hundred twenty five psi pressure classes. In 1966 the 50 and 125 psi pressure courses have been elevated to 75 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 published in 2010 with 25, 50, 75 and 150 psi strain lessons with the 250 psi class added in 2014. The high-performance butterfly valve standard was printed in 2018 and includes 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 toes per second).
The first AWWA quarter-turn ball valve normal, C507, for 6-in. through 48-in. ball valves in one hundred fifty, 250 and 300 psi pressure lessons 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 commonplace for resilient-seated cast-iron eccentric plug valves in 1991, the first a AWWA quarter-turn valve commonplace, C517, was not revealed until 2005. The 2005 size vary was three in. via 72 in. with a 175
Example butterfly valve differential strain (top) and move price management home windows (bottom)
stress 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) haven’t elevated the valve sizes or strain courses. No questions asked 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 decrease values.
The want for a rotary cone valve was recognized in 2018 and the AWWA Rotary Cone Valves, 6 Inch Through 60 Inch (150 mm through 1,500 mm), C522, is beneath growth. This normal will encompass the identical a hundred and fifty, 250 and 300 psi strain lessons and the identical fluid velocity designation of “D” (maximum 35 feet per second) as the current C507 ball valve commonplace.
In common, all of the valve sizes, flow charges and pressures have increased for the rationale that AWWA standard’s inception.
AWWA Manual M49 identifies 10 parts that affect operating torque for quarter-turn valves. These components fall into two general classes: (1) passive or friction-based parts, and (2) lively or dynamically generated elements. Because valve producers cannot know the precise piping system parameters when publishing torque values, published torques are usually restricted to the 5 elements of passive or friction-based components. These embody:
Passive torque elements:
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 active torque include:
Active torque components:
Disc weight and middle of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When contemplating all these numerous active torque components, it is potential 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’re being uncovered to larger service pressure and circulate price service situations. Since the quarter-turn valve’s closure member is at all times located in the flowing fluid, these higher service situations directly impression the valve. Operation of those valves require an actuator to rotate and/or maintain the closure member throughout the valve’s body as it reacts to all of the fluid pressures and fluid circulate dynamic situations.
In addition to the elevated service conditions, the valve sizes are also growing. The dynamic conditions of the flowing fluid have larger impact on the larger valve sizes. Therefore, the fluid dynamic effects turn into more necessary than static differential strain and friction loads. Valves may be leak and hydrostatically shell examined throughout fabrication. However, the total fluid circulate situations cannot be replicated earlier than web site set up.
Because of the development for increased valve sizes and elevated operating situations, it is increasingly necessary for the system designer, operator and proprietor of quarter-turn valves to raised understand the influence of system and fluid dynamics have on valve selection, development and use.
The AWWA Manual of Standard Practice M forty nine is dedicated to the understanding of quarter-turn valves including operating torque requirements, differential pressure, move circumstances, throttling, cavitation and system set up differences that directly influence the operation and profitable use of quarter-turn valves in waterworks methods.
The fourth edition of M49 is being developed to incorporate the modifications in the quarter-turn valve product requirements and installed system interactions. A new chapter might be devoted to strategies of management valve sizing for fluid move, pressure management and throttling in waterworks service. Feast contains explanations on the utilization of pressure, circulate price and cavitation graphical home windows to offer the consumer a radical image of valve efficiency over a range of anticipated system operating situations.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton began 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 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 concerned in quarter-turn valve and actuator engineering and design for 50 years and has been an energetic 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 also worked with the Electric Power Research Institute (EPRI) within the growth of their quarter-turn valve efficiency prediction strategies for the nuclear energy business.

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