Understanding Torque for Quarter-Turn Valves

Valve producers publish torques for his or her merchandise in order that actuation and mounting hardware can be properly selected. However, revealed torque values often characterize solely the seating or unseating torque for a valve at its rated pressure. While these are essential values for reference, published valve torques do not account for actual installation and working characteristics. In order to discover out the actual working torque for valves, it is essential to know the parameters of the piping methods into which they’re put in. Factors corresponding to installation orientation, direction of flow and fluid velocity of the media all impact the actual working torque of valves.
Trunnion mounted ball valve operated by a single appearing spring return actuator. Photo credit score: Val-Matic
The American Water Works Association (AWWA) publishes detailed data 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 printed in 2001 with torque calculations for butterfly valves, AWWA M49 is at present in its third version. In addition to data on butterfly valves, the present edition also consists of operating torque calculations for other quarter-turn valves including 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 printed in 1958 with 25, 50 and a hundred twenty five psi stress lessons. In 1966 the 50 and a hundred twenty five psi stress classes had been increased to seventy five and a hundred and fifty psi. The 250 psi pressure class was added in 2000. The 78-in. and bigger butterfly valve standard, C516, was first revealed in 2010 with 25, 50, seventy five and one hundred fifty psi pressure classes with the 250 psi class added in 2014. ตัววัดแรงดันน้ำมัน -performance butterfly valve commonplace was revealed in 2018 and consists of 275 and 500 psi pressure courses in addition to pushing the fluid flow velocities above class B (16 toes per second) to class C (24 feet per second) and class D (35 feet per second).
The first AWWA quarter-turn ball valve normal, C507, for 6-in. through 48-in. ball valves in one hundred fifty, 250 and 300 psi stress courses was published in 1973. In 2011, measurement range was elevated to 6-in. through 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 standard for resilient-seated cast-iron eccentric plug valves in 1991, the primary a AWWA quarter-turn valve normal, C517, was not revealed till 2005. The 2005 dimension vary was three in. by way of seventy two in. with a one hundred seventy five
Example butterfly valve differential stress (top) and circulate rate control home windows (bottom)
strain class for 3-in. through 12-in. sizes and one hundred fifty 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 used in wastewater service the place pressures and fluid velocities are maintained at decrease values.
The need 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 beneath improvement. This commonplace will encompass the same a hundred and fifty, 250 and 300 psi stress lessons and the same fluid velocity designation of “D” (maximum 35 toes per second) as the present C507 ball valve normal.
In general, all the valve sizes, flow rates and pressures have increased for the explanation that AWWA standard’s inception.
AWWA Manual M49 identifies 10 parts that have an result on operating torque for quarter-turn valves. These components fall into two general classes: (1) passive or friction-based elements, and (2) energetic or dynamically generated components. Because valve manufacturers can’t know the precise piping system parameters when publishing torque values, printed torques are usually restricted to the 5 elements of passive or friction-based components. These include:
Passive torque components:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The different 5 elements are impacted by system parameters corresponding to valve orientation, media and flow velocity. The parts that make up energetic torque embody:
Active torque elements:
Disc weight and middle of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When contemplating all these various active torque parts, it’s possible for the actual working torque to exceed the valve manufacturer’s published torque values.
Although quarter-turn valves have been used in the waterworks business for a century, they’re being exposed to higher service strain and move rate service circumstances. Since the quarter-turn valve’s closure member is always positioned within the flowing fluid, these larger service circumstances immediately influence the valve. Operation of these valves require an actuator to rotate and/or hold the closure member within the valve’s body as it reacts to all the fluid pressures and fluid flow dynamic conditions.
In addition to the elevated service situations, the valve sizes are additionally rising. The dynamic conditions of the flowing fluid have larger effect on the larger valve sizes. Therefore, the fluid dynamic effects become extra essential than static differential pressure and friction hundreds. Valves may be leak and hydrostatically shell examined during fabrication. However, the total fluid circulate circumstances cannot be replicated earlier than web site set up.
Because of the development for increased valve sizes and increased operating circumstances, it is more and more essential for the system designer, operator and proprietor of quarter-turn valves to raised perceive 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 stress, move circumstances, throttling, cavitation and system installation variations that directly influence the operation and profitable use of quarter-turn valves in waterworks techniques.
The fourth edition of M49 is being developed to include the changes in the quarter-turn valve product requirements and installed system interactions. A new chapter shall be devoted to strategies of control valve sizing for fluid flow, pressure management and throttling in waterworks service. This methodology contains explanations on the use of stress, circulate price and cavitation graphical home windows to supply the consumer a thorough picture of valve performance over a variety of anticipated system operating circumstances.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton began his career as a consulting engineer in 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 previously worked at Val-Matic as Director of Engineering. He has participated in requirements creating 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 lively member of each 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) in the development of their quarter-turn valve efficiency prediction methods for the nuclear energy business.

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