Understanding Torque for Quarter-Turn Valves

Valve manufacturers publish torques for their merchandise so that actuation and mounting hardware can be properly selected. However, published torque values typically represent only the seating or unseating torque for a valve at its rated stress. While these are important values for reference, published valve torques don’t account for actual installation and operating characteristics. In order to determine the actual working torque for valves, it is essential to grasp the parameters of the piping systems into which they’re put in. Factors corresponding to installation orientation, direction of move and fluid velocity of the media all influence the precise operating torque of valves.
Trunnion 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 operating torques for quarter-turn valves. This information seems in AWWA Manual M49 Quarter-Turn Valves: Head Loss, Torque, and Cavitation Analysis. Originally published in 2001 with torque calculations for butterfly valves, AWWA M49 is presently in its third version. In addition to info on butterfly valves, the current version additionally includes operating torque calculations for other quarter-turn valves together with plug valves and ball valves. Overall, this handbook identifies 10 parts 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. through 72-in. butterfly valves, C504, was printed in 1958 with 25, 50 and 125 psi pressure courses. In 1966 the 50 and one hundred twenty five psi strain courses were elevated to 75 and 150 psi. The 250 psi stress class was added in 2000. The 78-in. and larger butterfly valve normal, C516, was first printed in 2010 with 25, 50, seventy five and a hundred and fifty psi pressure classes with the 250 psi class added in 2014. The high-performance butterfly valve commonplace was published in 2018 and includes 275 and 500 psi pressure lessons in addition to pushing the fluid circulate 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 normal, C507, for 6-in. via 48-in. ball valves in one hundred fifty, 250 and 300 psi pressure courses was printed in 1973. In 2011, measurement vary was increased to 6-in. via 60-in. These valves have at all times 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 standard for resilient-seated cast-iron eccentric plug valves in 1991, the first a AWWA quarter-turn valve commonplace, C517, was not printed until 2005. The 2005 measurement vary was 3 in. through seventy two in. with a 175
Example butterfly valve differential pressure (top) and circulate rate control 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) haven’t elevated the valve sizes or strain lessons. The addition of the A velocity designation (8 fps) was added in the 2017 version. 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 by way of 1,500 mm), C522, is underneath development. This standard will encompass the identical a hundred and fifty, 250 and 300 psi stress courses and the identical fluid velocity designation of “D” (maximum 35 ft per second) as the current C507 ball valve normal.
In common, all the valve sizes, move charges and pressures have increased for the reason that AWWA standard’s inception.
AWWA Manual M49 identifies 10 parts that have an effect on operating torque for quarter-turn valves. These parts fall into two common classes: (1) passive or friction-based parts, and (2) energetic or dynamically generated parts. Because valve manufacturers cannot know the precise piping system parameters when publishing torque values, revealed torques are generally restricted to the 5 parts of passive or friction-based components. These embody:
Passive torque components:
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 similar to valve orientation, media and flow velocity. The components that make up lively torque embrace:
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 numerous energetic torque elements, it’s attainable for the actual working torque to exceed the valve manufacturer’s revealed 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 flow fee service circumstances. Since the quarter-turn valve’s closure member is always positioned within the flowing fluid, these greater service situations directly impact the valve. Operation of those valves require an actuator to rotate and/or hold the closure member inside the valve’s physique as it reacts to all of the fluid pressures and fluid flow dynamic situations.
In addition to the increased service circumstances, the valve sizes are additionally increasing. The dynamic circumstances of the flowing fluid have larger effect on the larger valve sizes. Therefore, the fluid dynamic results turn into extra essential than static differential pressure and friction hundreds. Valves may be leak and hydrostatically shell examined during fabrication. However, the full fluid flow conditions cannot be replicated before site installation.
Because of เครื่องมือวัดความดัน for elevated valve sizes and increased working conditions, it’s more and more essential for the system designer, operator and owner of quarter-turn valves to raised perceive the impact of system and fluid dynamics have on valve selection, construction and use.
The AWWA Manual of Standard Practice M forty nine is dedicated to the understanding of quarter-turn valves together with operating torque requirements, differential pressure, move situations, throttling, cavitation and system set up variations that directly influence the operation and successful use of quarter-turn valves in waterworks methods.
The fourth edition of M49 is being developed to include the changes within the quarter-turn valve product requirements and put in system interactions. A new chapter shall be dedicated to methods of control valve sizing for fluid move, strain control and throttling in waterworks service. This methodology contains explanations on using strain, circulate fee and cavitation graphical windows to supply the consumer a thorough picture of valve performance over a spread of anticipated system operating circumstances.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton started his career as a consulting engineer within 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 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 levels in Civil and Environmental Engineering together with Professional Engineering Registration.
John Holstrom has been involved 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 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) within the growth of their quarter-turn valve efficiency prediction methods for the nuclear power industry.

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