Understanding Torque for Quarter-Turn Valves

Valve manufacturers publish torques for his or her merchandise so that actuation and mounting hardware may be correctly chosen. However, printed torque values typically represent solely the seating or unseating torque for a valve at its rated stress. While these are essential values for reference, revealed valve torques do not account for actual set up and operating traits. In Unexplained to find out the actual working torque for valves, it is needed to know the parameters of the piping systems into which they are installed. 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 acting spring return actuator. Photo credit score: Val-Matic
The American Water Works Association (AWWA) publishes detailed data on calculating working 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 current edition additionally consists of working torque calculations for different quarter-turn valves together with plug valves and ball valves. Instant , this guide 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 normal for 3-in. through 72-in. butterfly valves, C504, was revealed in 1958 with 25, 50 and one hundred twenty five psi stress lessons. In 1966 the 50 and a hundred twenty five psi strain courses have been elevated to 75 and one hundred fifty psi. The 250 psi pressure class was added in 2000. The 78-in. and bigger butterfly valve standard, C516, was first printed in 2010 with 25, 50, 75 and one hundred fifty psi stress classes 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 as nicely as pushing the fluid flow velocities above class B (16 toes per second) to class C (24 toes 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 a hundred and fifty, 250 and 300 psi stress classes was revealed in 1973. In 2011, size vary was elevated to 6-in. through 60-in. These valves have all the time 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 primary a AWWA quarter-turn valve standard, C517, was not printed till 2005. The 2005 size vary was three in. via 72 in. with a one hundred seventy five
Example butterfly valve differential pressure (top) and move rate control home windows (bottom)
stress 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 increased the valve sizes or pressure courses. The addition of the A velocity designation (8 fps) was added within the 2017 version. This valve is primarily utilized in wastewater service the place pressures and fluid velocities are maintained at lower 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 underneath growth. This standard will encompass the same one hundred fifty, 250 and 300 psi strain lessons and the identical fluid velocity designation of “D” (maximum 35 ft per second) as the present C507 ball valve commonplace.
In general, all the valve sizes, circulate rates and pressures have elevated because the AWWA standard’s inception.
AWWA Manual M49 identifies 10 components that have an effect on working torque for quarter-turn valves. These parts fall into two general classes: (1) passive or friction-based elements, and (2) lively or dynamically generated parts. Because valve producers cannot know the actual piping system parameters when publishing torque values, revealed torques are usually limited to the 5 parts of passive or friction-based parts. These embody:
Passive torque parts:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The different 5 parts are impacted by system parameters such as valve orientation, media and flow velocity. The elements that make up energetic torque embody:
Active torque parts:
Disc weight and heart of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When contemplating all these numerous energetic torque components, it’s attainable for the actual working torque to exceed the valve manufacturer’s published torque values.
Although quarter-turn valves have been used in the waterworks trade for a century, they are being uncovered to larger service stress and move fee service conditions. Since the quarter-turn valve’s closure member is all the time positioned within the flowing fluid, these higher service circumstances directly impact the valve. Operation of those valves require an actuator to rotate and/or hold the closure member inside the valve’s body as it reacts to all the fluid pressures and fluid circulate dynamic situations.
In addition to the elevated service circumstances, the valve sizes are additionally growing. The dynamic circumstances of the flowing fluid have larger effect on the bigger valve sizes. Therefore, the fluid dynamic results turn into more important than static differential pressure and friction loads. Valves may be leak and hydrostatically shell tested throughout fabrication. However, the total fluid flow conditions can’t be replicated earlier than web site installation.
Because of the development for elevated valve sizes and increased working situations, it is increasingly essential for the system designer, operator and proprietor of quarter-turn valves to higher perceive the impression of system and fluid dynamics have on valve selection, building and use.
The AWWA Manual of Standard Practice M forty nine is dedicated to the understanding of quarter-turn valves together with working torque requirements, differential stress, circulate conditions, throttling, cavitation and system set up differences that immediately influence the operation and successful use of quarter-turn valves in waterworks systems.
The fourth edition of M49 is being developed to incorporate the adjustments within the quarter-turn valve product standards and put in system interactions. A new chapter will be devoted to strategies of control valve sizing for fluid flow, stress management and throttling in waterworks service. This methodology contains explanations on using stress, move rate and cavitation graphical windows to provide the consumer a radical picture of valve efficiency over a range of anticipated system working conditions.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton began his profession 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 beforehand worked at Val-Matic as Director of Engineering. He has participated in requirements 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 lively member of both 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) within the development of their quarter-turn valve efficiency prediction methods for the nuclear power industry.

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