Understanding Torque for Quarter-Turn Valves

Valve producers publish torques for their products in order that actuation and mounting hardware could be properly selected. However, printed torque values usually characterize solely the seating or unseating torque for a valve at its rated pressure. While these are important values for reference, published valve torques don’t account for actual set up and operating characteristics. In order to determine the actual working torque for valves, it’s necessary to grasp the parameters of the piping methods into which they are installed. Factors such as set up orientation, path of flow and fluid velocity of the media all influence the precise 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 at present in its third edition. In addition to data on butterfly valves, the present version also includes working torque calculations for other quarter-turn valves together with plug valves and ball valves. Overall, 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 standard for 3-in. via 72-in. butterfly valves, C504, was revealed in 1958 with 25, 50 and 125 psi pressure courses. In 1966 the 50 and one hundred twenty five psi pressure lessons were increased to seventy five and a hundred and fifty psi. The 250 psi strain class was added in 2000. The 78-in. and bigger butterfly valve commonplace, C516, was first printed in 2010 with 25, 50, 75 and a hundred and fifty psi pressure lessons with the 250 psi class added in 2014. The high-performance butterfly valve normal was printed in 2018 and contains 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 ft per second) and sophistication D (35 ft per second).
The first AWWA quarter-turn ball valve standard, C507, for 6-in. through 48-in. ball valves in one hundred fifty, 250 and 300 psi strain courses was published in 1973. In 2011, size vary was increased to 6-in. by way of 60-in. These valves have at all times 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 published till 2005. เกจวัดแรงดันไฟฟ้า was three in. through 72 in. with a one hundred seventy five
Example butterfly valve differential pressure (top) and flow price control 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 pressure classes. The addition of the A velocity designation (8 fps) was added within the 2017 edition. This valve is primarily utilized in wastewater service where pressures and fluid velocities are maintained at lower 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 underneath improvement. This commonplace will embody the identical a hundred and fifty, 250 and 300 psi stress lessons and the same fluid velocity designation of “D” (maximum 35 feet per second) as the current C507 ball valve standard.
In basic, all the valve sizes, flow rates and pressures have elevated since the AWWA standard’s inception.
AWWA Manual M49 identifies 10 elements that have an effect on working torque for quarter-turn valves. These elements fall into two basic categories: (1) passive or friction-based components, and (2) active or dynamically generated components. Because valve manufacturers can not know the precise piping system parameters when publishing torque values, revealed torques are usually limited to the five elements of passive or friction-based elements. These embody:
Passive torque elements:
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 circulate velocity. The elements that make up energetic torque embody:
Active torque parts:
Disc weight and middle of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When considering all these various energetic torque components, it is possible for the precise operating torque to exceed the valve manufacturer’s printed torque values.
Although quarter-turn valves have been used in the waterworks business for a century, they are being uncovered to larger service pressure and move rate service circumstances. Since the quarter-turn valve’s closure member is all the time situated in the flowing fluid, these higher service conditions instantly influence the valve. Operation of these valves require an actuator to rotate and/or hold the closure member inside the valve’s physique because it reacts to all of the fluid pressures and fluid flow dynamic situations.
In addition to the elevated service situations, the valve sizes are also increasing. The dynamic conditions of the flowing fluid have higher effect on the bigger valve sizes. Therefore, the fluid dynamic effects turn into extra important than static differential stress and friction loads. Valves may be leak and hydrostatically shell examined during fabrication. However, the full fluid circulate conditions can’t be replicated earlier than web site installation.
Because of the development for increased valve sizes and elevated operating circumstances, it is more and more essential for the system designer, operator and owner of quarter-turn valves to raised understand the impact of system and fluid dynamics have on valve choice, development and use.
The AWWA Manual of Standard Practice M forty nine is devoted to the understanding of quarter-turn valves including operating torque necessities, differential stress, flow circumstances, throttling, cavitation and system installation variations that immediately affect the operation and successful use of quarter-turn valves in waterworks methods.
The fourth version of M49 is being developed to include the modifications within the quarter-turn valve product requirements and put in system interactions. A new chapter will be devoted to strategies of management valve sizing for fluid move, pressure management and throttling in waterworks service. This methodology contains explanations on using stress, flow fee and cavitation graphical home windows to provide the person a radical image of valve efficiency over a spread of anticipated system operating conditions.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton began his profession 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 previously worked at Val-Matic as Director of Engineering. He has participated in requirements developing organizations, including AWWA, MSS, ASSE and API. Dalton holds BS and MS degrees in Civil and Environmental Engineering along 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 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 efficiency prediction strategies for the nuclear energy trade.

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