Understanding Torque for Quarter-Turn Valves

Valve producers publish torques for their products so that actuation and mounting hardware can be properly selected. However, revealed torque values typically characterize only the seating or unseating torque for a valve at its rated strain. While these are important values for reference, published valve torques don’t account for actual set up and working traits. In order to find out the actual working torque for valves, it’s needed to understand the parameters of the piping methods into which they are put in. Factors corresponding to installation orientation, path of move and fluid velocity of the media all impression the actual operating torque of valves.
Trunnion mounted ball valve operated by a single performing spring return actuator. Photo credit: Val-Matic
The American Water Works Association (AWWA) publishes detailed information 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 addition to information on butterfly valves, the present version additionally contains working torque calculations for different quarter-turn valves together with plug valves and ball valves. Overall, this manual identifies 10 parts of torque that can contribute to a quarter-turn valve’s operating torque.
Example torque calculation abstract graph
The first AWWA quarter-turn valve standard for 3-in. by way of 72-in. butterfly valves, C504, was printed in 1958 with 25, 50 and 125 psi pressure courses. In 1966 the 50 and one hundred twenty five psi stress classes were increased to seventy five and 150 psi. The 250 psi stress class was added in 2000. The 78-in. and bigger butterfly valve normal, C516, was first printed in 2010 with 25, 50, seventy five and one hundred fifty psi strain classes with the 250 psi class added in 2014. The high-performance butterfly valve normal was revealed in 2018 and consists of 275 and 500 psi strain lessons as well as pushing the fluid circulate velocities above class B (16 ft per second) to class C (24 feet per second) and sophistication D (35 ft per second).
The first AWWA quarter-turn ball valve standard, C507, for 6-in. by way of 48-in. ball valves in one hundred fifty, 250 and 300 psi strain courses was printed in 1973. In 2011, measurement range was increased to 6-in. via 60-in. These valves have all the time been designed for 35 ft per second (fps) most 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 standard, C517, was not published till 2005. The 2005 size range was three in. via seventy two in. with a a hundred seventy five
Example butterfly valve differential pressure (top) and flow rate control windows (bottom)
strain class for 3-in. by way of 12-in. sizes and 150 psi for the 14-in. via 72-in. The later editions (2009 and 2016) have not increased the valve sizes or strain lessons. The addition of the A velocity designation (8 fps) was added in the 2017 edition. This valve is primarily utilized in wastewater service where pressures and fluid velocities are maintained at decrease values.
เกจวัดแรงอัดกระบอกสูบ for a rotary cone valve was recognized 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 normal will encompass the identical 150, 250 and 300 psi strain courses and the identical fluid velocity designation of “D” (maximum 35 ft per second) as the present C507 ball valve standard.
In common, all the valve sizes, circulate rates and pressures have increased since the AWWA standard’s inception.
AWWA Manual M49 identifies 10 parts that affect operating torque for quarter-turn valves. These elements fall into two general classes: (1) passive or friction-based components, and (2) energetic or dynamically generated elements. Because valve producers can not know the actual piping system parameters when publishing torque values, printed torques are usually restricted to the 5 parts of passive or friction-based elements. These include:
Passive torque parts:
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 corresponding to valve orientation, media and move velocity. The elements that make up lively torque embody:
Active torque components:
Disc weight and middle of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When considering all these varied energetic torque parts, it’s possible for the precise operating 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 uncovered to larger service pressure and circulate fee service conditions. Since the quarter-turn valve’s closure member is all the time positioned in the flowing fluid, these higher service conditions directly influence the valve. Operation of these valves require an actuator to rotate and/or hold the closure member within the valve’s physique because it reacts to all of the fluid pressures and fluid flow dynamic circumstances.
In addition to the elevated service situations, the valve sizes are additionally growing. The dynamic situations of the flowing fluid have larger effect on the bigger valve sizes. Therefore, the fluid dynamic results become more essential than static differential stress and friction loads. Valves could be leak and hydrostatically shell examined during fabrication. However, the total fluid move situations can’t be replicated earlier than web site installation.
Because of the development for increased valve sizes and elevated working situations, it is more and more essential for the system designer, operator and owner of quarter-turn valves to higher understand the impact of system and fluid dynamics have on valve choice, construction and use.
The AWWA Manual of Standard Practice M 49 is dedicated to the understanding of quarter-turn valves together with working torque requirements, differential pressure, flow situations, throttling, cavitation and system set up 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 installed system interactions. A new chapter might be dedicated to methods of control valve sizing for fluid circulate, pressure management and throttling in waterworks service. This methodology contains explanations on the use of stress, circulate fee and cavitation graphical home windows to provide the consumer a thorough picture of valve efficiency over a variety of anticipated system operating situations.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton began his career 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 labored at Val-Matic as Director of Engineering. He has participated in standards growing 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 involved 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 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 labored with the Electric Power Research Institute (EPRI) within the improvement of their quarter-turn valve performance prediction strategies for the nuclear energy business.

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