Understanding Torque for Quarter-Turn Valves

Valve producers publish torques for their merchandise so that actuation and mounting hardware may be properly chosen. However, printed torque values usually characterize only the seating or unseating torque for a valve at its rated stress. While these are necessary values for reference, revealed valve torques do not account for precise installation and operating traits. In order to discover out the precise operating torque for valves, it is essential to grasp the parameters of the piping methods into which they are installed. Factors corresponding to set up orientation, path of circulate and fluid velocity of the media all impact the actual operating torque of valves.
เกจวัดแรงดันดิจิตอล mounted ball valve operated by a single appearing spring return actuator. Photo credit: Val-Matic
The American Water Works Association (AWWA) publishes detailed data on calculating working torques for quarter-turn valves. This information appears in AWWA Manual M49 Quarter-Turn Valves: Head Loss, Torque, and Cavitation Analysis. Originally printed in 2001 with torque calculations for butterfly valves, AWWA M49 is presently in its third edition. In addition to data on butterfly valves, the current version additionally includes operating torque calculations for other quarter-turn valves including plug valves and ball valves. Overall, this manual identifies 10 elements of torque that can contribute to a quarter-turn valve’s operating torque.
Example torque calculation summary graph
The first AWWA quarter-turn valve normal for 3-in. via 72-in. butterfly valves, C504, was published in 1958 with 25, 50 and one hundred twenty five psi stress lessons. In 1966 the 50 and 125 psi pressure classes had been elevated to 75 and a hundred and fifty psi. The 250 psi stress class was added in 2000. The 78-in. and bigger butterfly valve commonplace, C516, was first published in 2010 with 25, 50, 75 and 150 psi stress courses with the 250 psi class added in 2014. The high-performance butterfly valve normal was published in 2018 and consists of 275 and 500 psi pressure lessons as well as pushing the fluid flow velocities above class B (16 ft per second) to class C (24 ft per second) and sophistication D (35 toes per second).
The first AWWA quarter-turn ball valve standard, C507, for 6-in. via 48-in. ball valves in one hundred fifty, 250 and 300 psi pressure classes was published in 1973. In 2011, dimension range was elevated 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 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 revealed till 2005. The 2005 dimension vary was three in. via seventy two in. with a one hundred seventy five
Example butterfly valve differential pressure (top) and move rate control home windows (bottom)
strain class for 3-in. by way of 12-in. sizes and 150 psi for the 14-in. by way of 72-in. The later editions (2009 and 2016) have not elevated the valve sizes or strain courses. 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 need for a rotary cone valve was acknowledged in 2018 and the AWWA Rotary Cone Valves, 6 Inch Through 60 Inch (150 mm via 1,500 mm), C522, is beneath development. This normal will encompass the identical 150, 250 and 300 psi strain classes and the identical fluid velocity designation of “D” (maximum 35 ft per second) as the present C507 ball valve normal.
In general, all of the valve sizes, move charges and pressures have elevated since the AWWA standard’s inception.
AWWA Manual M49 identifies 10 parts that have an result on operating torque for quarter-turn valves. These parts fall into two basic classes: (1) passive or friction-based elements, and (2) active or dynamically generated elements. Because valve manufacturers can not know the actual piping system parameters when publishing torque values, published torques are typically restricted to the five parts of passive or friction-based elements. These embrace:
Passive torque parts:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The different five parts are impacted by system parameters corresponding to valve orientation, media and move velocity. The parts that make up lively torque embody:
Active torque elements:
Disc weight and center of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When considering all these various lively torque elements, it is potential for the precise working torque to exceed the valve manufacturer’s printed torque values.
Although quarter-turn valves have been used in the waterworks trade for a century, they are being uncovered to greater service stress and move fee service conditions. Since the quarter-turn valve’s closure member is at all times positioned in the flowing fluid, these larger service situations directly impression the valve. Operation of those valves require an actuator to rotate and/or hold the closure member throughout the valve’s body because it reacts to all the fluid pressures and fluid circulate dynamic situations.
In addition to the increased service situations, the valve sizes are additionally rising. The dynamic conditions of the flowing fluid have greater impact on the larger valve sizes. Therefore, the fluid dynamic results turn into extra important than static differential pressure and friction hundreds. Valves can be leak and hydrostatically shell tested during fabrication. However, the total fluid circulate conditions cannot be replicated before web site set up.
Because of the trend for increased valve sizes and increased working conditions, it is increasingly necessary for the system designer, operator and proprietor of quarter-turn valves to raised perceive the impression of system and fluid dynamics have on valve choice, building and use.
The AWWA Manual of Standard Practice M forty nine is devoted to the understanding of quarter-turn valves together with working torque necessities, differential strain, flow situations, throttling, cavitation and system set up variations that directly influence the operation and profitable use of quarter-turn valves in waterworks systems.
The fourth edition of M49 is being developed to incorporate the modifications within the quarter-turn valve product requirements and put in system interactions. A new chapter might be dedicated to strategies of control valve sizing for fluid flow, strain management and throttling in waterworks service. This methodology consists of explanations on using strain, circulate price and cavitation graphical windows to offer the person a thorough image of valve efficiency over a range of anticipated system operating circumstances.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton started 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 labored at Val-Matic as Director of Engineering. He has participated in requirements growing 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 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 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 worked with the Electric Power Research Institute (EPRI) within the improvement of their quarter-turn valve performance prediction methods for the nuclear energy industry.

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