Valve manufacturers publish torques for his or her merchandise in order that actuation and mounting hardware may be properly selected. However, revealed torque values typically represent solely the seating or unseating torque for a valve at its rated strain. While these are necessary values for reference, printed valve torques do not account for precise installation and working characteristics. In order to find out the actual operating torque for valves, it’s necessary to understand the parameters of the piping systems into which they’re put in. Factors corresponding to installation orientation, course of circulate and fluid velocity of the media all impression the precise 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 info 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 info on butterfly valves, the current edition also consists of operating torque calculations for different quarter-turn valves including plug valves and ball valves. Overall, this manual identifies 10 elements of torque that can contribute to a quarter-turn valve’s operating torque.
Example torque calculation summary 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 125 psi pressure lessons have been elevated to seventy five and 150 psi. The 250 psi stress class was added in 2000. The 78-in. and bigger butterfly valve commonplace, C516, was first printed in 2010 with 25, 50, seventy five and one hundred fifty psi pressure classes with the 250 psi class added in 2014. The high-performance butterfly valve commonplace was published in 2018 and consists of 275 and 500 psi pressure classes as well as pushing the fluid circulate velocities above class B (16 ft per second) to class C (24 toes per second) and class D (35 ft per second).
The first AWWA quarter-turn ball valve normal, C507, for 6-in. via 48-in. ball valves in a hundred and fifty, 250 and 300 psi strain classes was printed in 1973. In 2011, dimension vary was increased to 6-in. by way of 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 standard, C517, was not printed till 2005. The 2005 dimension vary was three in. by way of 72 in. with a 175
Example butterfly valve differential pressure (top) and circulate rate control home windows (bottom)
stress class for 3-in. via 12-in. sizes and 150 psi for the 14-in. by way of 72-in. The later editions (2009 and 2016) haven’t elevated the valve sizes or stress courses. The addition of the A velocity designation (8 fps) was added within the 2017 version. This valve is primarily used in wastewater service the place 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 via 1,500 mm), C522, is under growth. This normal will encompass the same 150, 250 and 300 psi stress classes and the identical fluid velocity designation of “D” (maximum 35 ft per second) as the present C507 ball valve commonplace.
In common, all of the valve sizes, circulate charges and pressures have elevated for the explanation that AWWA standard’s inception.
AWWA Manual M49 identifies 10 parts that have an result on working torque for quarter-turn valves. These elements fall into two basic categories: (1) passive or friction-based elements, and (2) energetic or dynamically generated parts. Because valve producers cannot know the actual piping system parameters when publishing torque values, revealed torques are usually restricted to the 5 components of passive or friction-based parts. These embody:
Passive torque components:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The different five components are impacted by system parameters such as valve orientation, media and flow velocity. The elements that make up active torque embody:
Active torque parts:
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 elements, it is possible for the actual working torque to exceed the valve manufacturer’s revealed torque values.
Although quarter-turn valves have been used within the waterworks trade for a century, they are being uncovered to larger service strain and flow price service circumstances. Since the quarter-turn valve’s closure member is all the time situated within the flowing fluid, these greater service conditions 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 circulate dynamic circumstances.
In addition to the elevated service conditions, the valve sizes are additionally increasing. The dynamic circumstances of the flowing fluid have greater effect on the bigger valve sizes. Therefore, the fluid dynamic results turn into extra important than static differential pressure and friction loads. Valves can be leak and hydrostatically shell tested during fabrication. However, the complete fluid flow situations cannot be replicated before site installation.
Because of the pattern for elevated valve sizes and increased working circumstances, it’s increasingly important for the system designer, operator and proprietor of quarter-turn valves to higher understand the impact of system and fluid dynamics have on valve selection, building and use.
The AWWA Manual of Standard Practice M 49 is devoted to the understanding of quarter-turn valves together with operating torque requirements, differential pressure, flow circumstances, throttling, cavitation and system installation differences that directly affect the operation and successful use of quarter-turn valves in waterworks methods.
The fourth version of M49 is being developed to incorporate the changes within the quarter-turn valve product standards and installed system interactions. A new chapter will be dedicated to strategies of control valve sizing for fluid circulate, stress control and throttling in waterworks service. This methodology includes explanations on using stress, circulate rate and cavitation graphical windows to provide the person an intensive picture of valve efficiency over a spread of anticipated system working circumstances.
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About the Authors
Steve Dalton began his profession as a consulting engineer in the waterworks business in Chicago. เกจวัดแรงดันลม10bar 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 creating organizations, together with 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 additionally labored with the Electric Power Research Institute (EPRI) in the development of their quarter-turn valve efficiency prediction strategies for the nuclear energy industry.