Understanding Torque for Quarter-Turn Valves

Valve producers publish torques for his or her products so that actuation and mounting hardware may be properly chosen. However, printed torque values typically represent only the seating or unseating torque for a valve at its rated stress. While these are essential values for reference, printed valve torques do not account for actual set up and operating traits. In order to find out the precise operating torque for valves, it is essential to know the parameters of the piping methods into which they’re installed. Factors similar to set up orientation, direction of move and fluid velocity of the media all impression the actual operating 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 information 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 version. In addition to information on butterfly valves, the current version additionally includes working torque calculations for other quarter-turn valves including plug valves and ball valves. Overall, this handbook identifies 10 elements of torque that can contribute to a quarter-turn valve’s working torque.
Example torque calculation abstract graph
The first AWWA quarter-turn valve commonplace for 3-in. by way of 72-in. butterfly valves, C504, was published in 1958 with 25, 50 and one hundred twenty five psi pressure courses. In 1966 the 50 and one hundred twenty five psi pressure lessons have been elevated to seventy five and 150 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, 75 and a hundred and fifty psi stress courses with the 250 psi class added in 2014. The high-performance butterfly valve commonplace was printed in 2018 and includes 275 and 500 psi stress courses as nicely as pushing the fluid circulate velocities above class B (16 ft per second) to class C (24 toes per second) and sophistication D (35 feet per second).
The first AWWA quarter-turn ball valve commonplace, C507, for 6-in. through 48-in. ball valves in a hundred and fifty, 250 and 300 psi strain lessons was printed in 1973. In 2011, size vary was elevated to 6-in. via 60-in. These valves have all the time 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 commonplace, C517, was not published until 2005. The 2005 measurement vary was 3 in. through 72 in. with a 175
Example butterfly valve differential pressure (top) and circulate fee management windows (bottom)
pressure class for 3-in. via 12-in. sizes and one hundred fifty psi for the 14-in. through 72-in. The later editions (2009 and 2016) have not increased the valve sizes or pressure courses. The addition of the A velocity designation (8 fps) was added within the 2017 edition. This valve is primarily used in wastewater service where pressures and fluid velocities are maintained at lower values.
The want 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 underneath development. This normal will encompass the same one hundred fifty, 250 and 300 psi strain courses and the same fluid velocity designation of “D” (maximum 35 feet per second) as the present C507 ball valve standard.
In common, all of the valve sizes, move rates and pressures have elevated since the AWWA standard’s inception.
AWWA Manual M49 identifies 10 elements that have an result on operating torque for quarter-turn valves. These elements fall into two common categories: (1) passive or friction-based parts, and (2) lively or dynamically generated elements. Because valve producers cannot know the precise piping system parameters when publishing torque values, published torques are usually limited to the 5 components 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 5 components are impacted by system parameters similar to valve orientation, media and move velocity. The parts that make up energetic torque embody:
Active torque elements:
Disc weight and heart of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When considering all these numerous active torque components, it’s possible for the actual operating torque to exceed the valve manufacturer’s revealed torque values.
Although quarter-turn valves have been used within the waterworks industry for a century, they are being exposed to larger service strain and circulate price service situations. Since the quarter-turn valve’s closure member is all the time situated in the flowing fluid, these larger service conditions immediately impact the valve. Operation of these valves require an actuator to rotate and/or hold the closure member throughout the valve’s physique as it reacts to all the fluid pressures and fluid circulate dynamic situations.
In addition to the increased service conditions, the valve sizes are additionally rising. The dynamic conditions of the flowing fluid have greater effect on the larger valve sizes. Therefore, the fluid dynamic effects turn into extra necessary than static differential stress and friction hundreds. Valves may be leak and hydrostatically shell tested during fabrication. However, the total fluid flow circumstances cannot be replicated earlier than site installation.
Because of the development for elevated valve sizes and elevated operating situations, it’s more and more important for the system designer, operator and owner of quarter-turn valves to higher perceive the influence of system and fluid dynamics have on valve choice, development and use.
pressure gauge ไฮ ด รอ ลิ ค of Standard Practice M forty nine is dedicated to the understanding of quarter-turn valves including working torque requirements, differential stress, move circumstances, throttling, cavitation and system set up variations that directly affect the operation and successful 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 management valve sizing for fluid flow, pressure control and throttling in waterworks service. This methodology consists of explanations on using stress, move price and cavitation graphical windows to supply the user an intensive picture of valve performance over a spread of anticipated system working circumstances.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton started his profession 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 beforehand worked at Val-Matic as Director of Engineering. He has participated in standards developing 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 energetic member of both 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) within the growth of their quarter-turn valve performance prediction strategies for the nuclear energy business.

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