Understanding Torque for Quarter-Turn Valves

Valve producers publish torques for his or her products in order that actuation and mounting hardware may be correctly selected. However, printed torque values typically symbolize solely the seating or unseating torque for a valve at its rated strain. While these are important values for reference, printed valve torques don’t account for precise set up and working traits. In order to find out the actual working torque for valves, it’s necessary to understand the parameters of the piping techniques into which they are installed. Factors such as installation orientation, path of flow and fluid velocity of the media all impact the precise operating torque of valves.
Trunnion mounted ball valve operated by a single acting 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 information seems 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 version. In addition to data on butterfly valves, the current edition additionally contains working torque calculations for other quarter-turn valves including plug valves and ball valves. Overall, this handbook identifies 10 parts of torque that may contribute to a quarter-turn valve’s operating torque.
Example torque calculation summary graph
The first AWWA quarter-turn valve commonplace for 3-in. through 72-in. butterfly valves, C504, was printed in 1958 with 25, 50 and 125 psi pressure classes. In 1966 the 50 and one hundred twenty five psi stress courses were elevated to 75 and one hundred fifty psi. The 250 psi strain class was added in 2000. The 78-in. and larger butterfly valve commonplace, C516, was first published in 2010 with 25, 50, seventy five and one hundred fifty psi pressure courses with the 250 psi class added in 2014. The high-performance butterfly valve normal was published in 2018 and includes 275 and 500 psi stress classes as nicely as pushing the fluid circulate velocities above class B (16 ft per second) to class C (24 ft per second) and sophistication D (35 feet per second).
The first AWWA quarter-turn ball valve standard, C507, for 6-in. by way of 48-in. ball valves in 150, 250 and 300 psi strain courses was revealed in 1973. In 2011, size range was elevated to 6-in. through 60-in. These valves have always 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 commonplace for resilient-seated cast-iron eccentric plug valves in 1991, the primary a AWWA quarter-turn valve standard, C517, was not revealed until 2005. The 2005 dimension range was three in. through seventy two in. with a a hundred seventy five
Example butterfly valve differential stress (top) and move rate control home windows (bottom)
stress class for 3-in. via 12-in. sizes and one hundred fifty psi for the 14-in. by way of 72-in. เกจวัดแรงดันลม10bar (2009 and 2016) haven’t increased the valve sizes or stress 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.
The need for a rotary cone valve was acknowledged in 2018 and the AWWA Rotary Cone Valves, 6 Inch Through 60 Inch (150 mm through 1,500 mm), C522, is underneath development. This normal will embody the identical 150, 250 and 300 psi strain courses and the same fluid velocity designation of “D” (maximum 35 toes per second) as the current C507 ball valve commonplace.
In basic, all of the valve sizes, circulate charges and pressures have elevated for the rationale that AWWA standard’s inception.
AWWA Manual M49 identifies 10 parts that affect working torque for quarter-turn valves. These components fall into two common categories: (1) passive or friction-based components, and (2) lively or dynamically generated elements. Because valve manufacturers can’t know the precise piping system parameters when publishing torque values, published torques are typically limited to the five parts 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 other five components are impacted by system parameters corresponding to valve orientation, media and flow velocity. The parts that make up active torque embrace:
Active torque elements:
Disc weight and middle of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When considering all these varied active torque elements, it’s possible for the actual working torque to exceed the valve manufacturer’s printed torque values.
Although quarter-turn valves have been used within the waterworks trade for a century, they’re being uncovered to greater service stress and circulate fee service conditions. Since the quarter-turn valve’s closure member is always situated in the flowing fluid, these greater service circumstances instantly impression the valve. Operation of these valves require an actuator to rotate and/or maintain the closure member within the valve’s body because it reacts to all the fluid pressures and fluid circulate dynamic conditions.
In addition to the elevated service situations, the valve sizes are also increasing. The dynamic situations of the flowing fluid have greater impact on the larger valve sizes. Therefore, the fluid dynamic effects become more important than static differential stress and friction hundreds. Valves could be leak and hydrostatically shell examined throughout fabrication. However, the full fluid circulate situations cannot be replicated before site set up.
Because of the development for elevated valve sizes and increased working circumstances, it’s more and more essential for the system designer, operator and proprietor of quarter-turn valves to higher understand the impression of system and fluid dynamics have on valve choice, development 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 pressure, move circumstances, throttling, cavitation and system installation differences that directly affect the operation and profitable use of quarter-turn valves in waterworks methods.
The fourth version of M49 is being developed to incorporate the changes within the quarter-turn valve product requirements and put in system interactions. A new chapter will be dedicated to methods of management valve sizing for fluid circulate, strain control and throttling in waterworks service. This methodology contains explanations on the usage of strain, move price and cavitation graphical windows to offer the consumer a radical image of valve efficiency over a spread of anticipated system working situations.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton started his profession as a consulting engineer within 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 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 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 labored with the Electric Power Research Institute (EPRI) in the growth of their quarter-turn valve efficiency prediction strategies for the nuclear power trade.

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