Valve producers publish torques for their merchandise so that actuation and mounting hardware can be properly chosen. However, printed torque values typically represent solely the seating or unseating torque for a valve at its rated stress. While these are necessary values for reference, printed valve torques do not account for precise installation and operating characteristics. In order to discover out the actual working torque for valves, it’s essential to grasp the parameters of the piping techniques into which they’re put in. Factors similar to set up orientation, course of circulate and fluid velocity of the media all influence the precise operating torque of valves.
Trunnion mounted ball valve operated by a single acting 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 printed in 2001 with torque calculations for butterfly valves, AWWA M49 is presently in its third edition. In addition to information on butterfly valves, the current edition also includes working torque calculations for different quarter-turn valves together with plug valves and ball valves. Overall, this manual identifies 10 components of torque that can contribute to a quarter-turn valve’s working torque.
Example torque calculation summary graph
AWWA QUARTER-TURN VALVE HISTORY
The first AWWA quarter-turn valve normal for 3-in. through 72-in. butterfly valves, C504, was published in 1958 with 25, 50 and 125 psi pressure lessons. In 1966 the 50 and 125 psi pressure courses were increased to 75 and one hundred fifty psi. The 250 psi stress class was added in 2000. The 78-in. and larger butterfly valve commonplace, C516, was first revealed in 2010 with 25, 50, 75 and a hundred and fifty psi strain 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 strain classes in addition to pushing the fluid flow velocities above class B (16 feet per second) to class C (24 ft per second) and sophistication D (35 toes per second).
The first AWWA quarter-turn ball valve commonplace, C507, for 6-in. through 48-in. ball valves in one hundred fifty, 250 and 300 psi pressure classes was published in 1973. In 2011, size vary was elevated to 6-in. through 60-in. These valves have always 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 normal for resilient-seated cast-iron eccentric plug valves in 1991, the first a AWWA quarter-turn valve standard, C517, was not printed till 2005. The 2005 size vary was 3 in. by way of seventy two in. with a 175
Example butterfly valve differential pressure (top) and move price management home windows (bottom)
stress class for 3-in. by way of 12-in. sizes and 150 psi for the 14-in. via 72-in. The later editions (2009 and 2016) have not increased the valve sizes or stress classes. The addition of the A velocity designation (8 fps) was added within the 2017 version. 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 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 improvement. This standard will encompass the same 150, 250 and 300 psi pressure classes and the same fluid velocity designation of “D” (maximum 35 toes per second) as the present C507 ball valve commonplace.
In basic, all of the valve sizes, flow charges and pressures have increased since the AWWA standard’s inception.
COMPONENTS OF OPERATING TORQUE
AWWA Manual M49 identifies 10 parts that affect operating torque for quarter-turn valves. These components fall into two basic classes: (1) passive or friction-based components, and (2) energetic or dynamically generated elements. Because valve producers can’t know the actual piping system parameters when publishing torque values, revealed torques are typically limited to the five elements of passive or friction-based parts. These embody:
Passive torque elements:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The different 5 components are impacted by system parameters similar to valve orientation, media and circulate velocity. The components that make up lively torque embody:
Active torque elements:
Disc weight and middle of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When considering all these varied active torque parts, it is potential for the actual working torque to exceed the valve manufacturer’s revealed torque values.
WHY IS M49 MORE IMPORTANT TODAY?
Although quarter-turn valves have been used within the waterworks business for a century, they’re being exposed to larger service strain and circulate fee service conditions. Since Well respected -turn valve’s closure member is always situated in the flowing fluid, these larger service situations immediately influence the valve. Operation of these valves require an actuator to rotate and/or hold the closure member throughout the valve’s body as it reacts to all the fluid pressures and fluid move 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 bigger valve sizes. Therefore, the fluid dynamic effects turn out to be more essential than static differential stress and friction hundreds. Valves may be leak and hydrostatically shell examined throughout fabrication. However, the complete fluid move circumstances cannot be replicated before web site set up.
Because of the trend for increased valve sizes and increased working situations, it’s more and more important for the system designer, operator and proprietor of quarter-turn valves to higher perceive the influence of system and fluid dynamics have on valve selection, construction and use.
The AWWA Manual of Standard Practice M 49 is dedicated to the understanding of quarter-turn valves including working torque necessities, differential pressure, flow situations, throttling, cavitation and system installation differences that directly affect the operation and successful use of quarter-turn valves in waterworks systems.
AWWA MANUAL OF STANDARD PRACTICE M49 4TH EDITION DEVELOPMENTS
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 dedicated to methods of control valve sizing for fluid flow, strain control and throttling in waterworks service. This methodology consists of explanations on using stress, flow price and cavitation graphical windows to supply the consumer a radical image of valve performance over a spread of anticipated system working situations.
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 requirements developing 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 involved in quarter-turn valve and actuator engineering and design for 50 years and has been an lively 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 also worked with the Electric Power Research Institute (EPRI) within the development of their quarter-turn valve efficiency prediction strategies for the nuclear power business.
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