Understanding Torque for Quarter-Turn Valves

Valve manufacturers publish torques for his or her merchandise in order that actuation and mounting hardware could be correctly chosen. However, published torque values typically characterize only the seating or unseating torque for a valve at its rated pressure. While these are important values for reference, printed valve torques don’t account for actual set up and operating traits. In order to discover out the precise working torque for valves, it is needed to understand the parameters of the piping techniques into which they’re put in. Factors such as set up orientation, direction of circulate and fluid velocity of the media all impact the precise working torque of valves.
Trunnion mounted ball valve operated by a single performing spring return actuator. Photo credit: Val-Matic
The American Water Works Association (AWWA) publishes detailed information 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 printed in 2001 with torque calculations for butterfly valves, AWWA M49 is currently in its third edition. In addition to data on butterfly valves, the present version additionally includes working torque calculations for different quarter-turn valves including plug valves and ball valves. Overall, this guide identifies 10 parts of torque that may 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 pressure courses. In 1966 the 50 and a hundred twenty five psi pressure lessons had been increased to seventy five and one hundred fifty psi. The 250 psi pressure class was added in 2000. The 78-in. and larger butterfly valve commonplace, C516, was first printed in 2010 with 25, 50, seventy five and 150 psi pressure lessons with the 250 psi class added in 2014. The high-performance butterfly valve commonplace was printed in 2018 and contains 275 and 500 psi stress classes in addition to pushing the fluid flow velocities above class B (16 ft per second) to class C (24 ft per second) and class D (35 ft per second).
The first AWWA quarter-turn ball valve normal, C507, for 6-in. by way of 48-in. ball valves in 150, 250 and 300 psi pressure classes was printed 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) most fluid velocity. เกจวัดความดันน้ำ 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 until 2005. The 2005 dimension range was 3 in. through seventy two in. with a 175
Example butterfly valve differential pressure (top) and flow fee control windows (bottom)
stress class for 3-in. by way of 12-in. sizes and one hundred fifty psi for the 14-in. through 72-in. The later editions (2009 and 2016) haven’t elevated the valve sizes or strain courses. 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 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 under development. This normal will encompass the same 150, 250 and 300 psi strain classes and the same fluid velocity designation of “D” (maximum 35 toes per second) as the present C507 ball valve normal.
In basic, all the valve sizes, circulate rates and pressures have elevated since the AWWA standard’s inception.
AWWA Manual M49 identifies 10 elements that have an result on working torque for quarter-turn valves. These parts fall into two general categories: (1) passive or friction-based parts, and (2) active or dynamically generated elements. Because valve manufacturers can’t know the precise piping system parameters when publishing torque values, published torques are usually limited to the 5 components of passive or friction-based elements. These embody:
Passive torque components:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The other 5 components are impacted by system parameters corresponding to valve orientation, media and flow velocity. The elements that make up lively torque include:
Active torque components:
Disc weight and center of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When considering all these varied energetic torque elements, it is possible for the precise operating torque to exceed the valve manufacturer’s published torque values.
Although quarter-turn valves have been used within the waterworks business for a century, they are being exposed to higher service strain and move rate service situations. Since the quarter-turn valve’s closure member is always positioned within the flowing fluid, these greater service conditions immediately impression the valve. Operation of those valves require an actuator to rotate and/or hold the closure member throughout the valve’s physique because it reacts to all the fluid pressures and fluid move dynamic circumstances.
In addition to the increased service situations, the valve sizes are also increasing. The dynamic circumstances of the flowing fluid have larger impact on the larger valve sizes. Therefore, the fluid dynamic results turn out to be extra important than static differential strain and friction hundreds. Valves may be leak and hydrostatically shell examined throughout fabrication. However, the full fluid circulate conditions can’t be replicated before site installation.
Because of the development for increased valve sizes and elevated working situations, it’s increasingly essential for the system designer, operator and owner of quarter-turn valves to better perceive the impact of system and fluid dynamics have on valve choice, development and use.
The AWWA Manual of Standard Practice M 49 is devoted to the understanding of quarter-turn valves together with working torque requirements, differential pressure, circulate situations, throttling, cavitation and system set up variations that instantly influence the operation and profitable use of quarter-turn valves in waterworks systems.
The fourth version of M49 is being developed to include the changes within the quarter-turn valve product requirements and installed system interactions. A new chapter might be dedicated to strategies of management valve sizing for fluid flow, stress management and throttling in waterworks service. This methodology includes explanations on the utilization of stress, circulate price and cavitation graphical home windows to supply the consumer an intensive picture of valve performance over a range of anticipated system operating conditions.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton started his career as a consulting engineer within 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 beforehand labored at Val-Matic as Director of Engineering. He has participated in requirements developing organizations, including AWWA, MSS, ASSE and API. เกจวัดแรงดันแก๊สco2 holds BS and MS levels in Civil and Environmental Engineering along 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) in the development of their quarter-turn valve performance prediction methods for the nuclear energy trade.

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