Understanding Torque for Quarter-Turn Valves

Valve manufacturers publish torques for their merchandise in order that actuation and mounting hardware could be correctly selected. However, printed torque values usually represent only the seating or unseating torque for a valve at its rated strain. While these are necessary values for reference, printed valve torques don’t account for actual installation and operating traits. In order to determine the precise working torque for valves, it is essential to grasp the parameters of the piping systems into which they’re put in. Factors similar to set up orientation, course of flow and fluid velocity of the media all impression the actual working torque of valves.
Trunnion mounted ball valve operated by a single acting spring return actuator. Photo credit score: Val-Matic
The American Water Works Association (AWWA) publishes detailed information on calculating operating 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 currently in its third edition. In addition to data on butterfly valves, the present edition also consists of working torque calculations for different quarter-turn valves including 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 commonplace for 3-in. through 72-in. butterfly valves, C504, was printed in 1958 with 25, 50 and one hundred twenty five psi strain lessons. In 1966 the 50 and 125 psi strain classes had been elevated to 75 and a hundred and fifty psi. The 250 psi strain class was added in 2000. The 78-in. and bigger butterfly valve commonplace, C516, was first published in 2010 with 25, 50, 75 and a hundred and fifty psi strain lessons with the 250 psi class added in 2014. The high-performance butterfly valve normal was published in 2018 and includes 275 and 500 psi strain classes as properly as pushing the fluid flow velocities above class B (16 feet per second) to class C (24 feet per second) and sophistication D (35 ft per second).
The first AWWA quarter-turn ball valve standard, C507, for 6-in. through 48-in. ball valves in one hundred fifty, 250 and 300 psi strain courses was revealed in 1973. In 2011, size range was increased to 6-in. through 60-in. These valves have always 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 commonplace 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 size range was three in. through 72 in. with a a hundred seventy five
Example butterfly valve differential strain (top) and circulate price control windows (bottom)
pressure class for 3-in. by way of 12-in. sizes and one hundred fifty psi for the 14-in. by way of 72-in. The later editions (2009 and 2016) haven’t increased the valve sizes or pressure classes. Under the table of the A velocity designation (8 fps) was added in the 2017 edition. This valve is primarily used in wastewater service the place pressures and fluid velocities are maintained at lower values.
The need 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 beneath growth. This commonplace will encompass the same one hundred fifty, 250 and 300 psi strain classes and the identical fluid velocity designation of “D” (maximum 35 feet per second) as the current C507 ball valve commonplace.
In general, all of the valve sizes, circulate charges and pressures have increased since the AWWA standard’s inception.
AWWA Manual M49 identifies 10 components that affect operating torque for quarter-turn valves. These components fall into two general classes: (1) passive or friction-based components, and (2) active or dynamically generated elements. Because valve manufacturers cannot know the actual piping system parameters when publishing torque values, published torques are usually restricted to the five parts of passive or friction-based elements. These include:
Passive torque parts:
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 corresponding to valve orientation, media and circulate velocity. The parts that make up lively torque embrace:
Active torque parts:
Disc weight and center of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When contemplating all these numerous energetic torque parts, it is potential for the actual operating torque to exceed the valve manufacturer’s published torque values.
Although quarter-turn valves have been used within the waterworks trade for a century, they are being exposed to higher service pressure and circulate fee service conditions. Since the quarter-turn valve’s closure member is at all times positioned within the flowing fluid, these higher service conditions directly impact the valve. Operation of those valves require an actuator to rotate and/or maintain the closure member within the valve’s physique because it reacts to all the fluid pressures and fluid move dynamic circumstances.
In addition to the increased service circumstances, the valve sizes are additionally increasing. The dynamic situations of the flowing fluid have greater effect on the bigger valve sizes. Therefore, the fluid dynamic results turn into more necessary than static differential pressure and friction hundreds. Valves may be leak and hydrostatically shell examined throughout fabrication. However, the complete fluid move situations can’t be replicated earlier than website set up.
Because of the development for increased valve sizes and elevated working circumstances, 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 choice, construction and use.
The AWWA Manual of Standard Practice M forty nine is devoted to the understanding of quarter-turn valves including operating torque necessities, differential stress, flow conditions, throttling, cavitation and system installation differences that instantly affect the operation and successful 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 standards and put in system interactions. A new chapter shall be devoted to strategies of control valve sizing for fluid flow, stress control and throttling in waterworks service. This methodology contains explanations on the use of pressure, flow price and cavitation graphical home windows to offer the user an intensive picture of valve performance over a range of anticipated system working 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 standards developing organizations, including AWWA, MSS, ASSE and API. Dalton holds BS and MS degrees 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 worked with the Electric Power Research Institute (EPRI) in the growth of their quarter-turn valve efficiency prediction strategies for the nuclear energy industry.

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