Understanding Torque for Quarter-Turn Valves

Valve manufacturers publish torques for their merchandise in order that actuation and mounting hardware can be properly chosen. However, revealed torque values typically characterize solely the seating or unseating torque for a valve at its rated stress. While these are necessary values for reference, revealed valve torques don’t account for precise installation and operating traits. In order to find out the precise operating torque for valves, it is essential to know the parameters of the piping techniques into which they’re installed. Factors similar to installation orientation, course of circulate and fluid velocity of the media all influence the actual operating 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 data 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 published in 2001 with torque calculations for butterfly valves, AWWA M49 is presently in its third edition. In addition to info on butterfly valves, the present edition additionally contains working torque calculations for different quarter-turn valves including plug valves and ball valves. Overall, this guide identifies 10 components of torque that may contribute to a quarter-turn valve’s operating torque.
Example torque calculation abstract graph
The first AWWA quarter-turn valve commonplace for 3-in. through 72-in. butterfly valves, C504, was published in 1958 with 25, 50 and a hundred twenty five psi pressure lessons. In 1966 the 50 and a hundred twenty five psi pressure lessons were elevated to seventy five and one hundred fifty psi. The 250 psi stress class was added in 2000. The 78-in. and larger butterfly valve standard, C516, was first published in 2010 with 25, 50, 75 and one hundred fifty psi stress courses with the 250 psi class added in 2014. The high-performance butterfly valve commonplace was printed in 2018 and consists of 275 and 500 psi stress lessons in addition to pushing the fluid move 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 150, 250 and 300 psi pressure lessons was revealed in 1973. In 2011, measurement vary was increased to 6-in. through 60-in. These valves have at all times 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 commonplace for resilient-seated cast-iron eccentric plug valves in 1991, the primary a AWWA quarter-turn valve normal, C517, was not published till 2005. The 2005 size vary was 3 in. via 72 in. with a a hundred seventy five
Example butterfly valve differential strain (top) and move rate control windows (bottom)
strain class for 3-in. by way of 12-in. sizes and 150 psi for the 14-in. through 72-in. The later editions (2009 and 2016) have not increased the valve sizes or stress lessons. The addition of the A velocity designation (8 fps) was added in 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 acknowledged in 2018 and the AWWA Rotary Cone Valves, 6 Inch Through 60 Inch (150 mm through 1,500 mm), C522, is underneath development. This standard will encompass the identical one hundred fifty, 250 and 300 psi strain lessons and the same fluid velocity designation of “D” (maximum 35 ft per second) as the current C507 ball valve normal.
In general, all of the valve sizes, move rates and pressures have increased because the AWWA standard’s inception.
AWWA Manual M49 identifies 10 parts that affect operating torque for quarter-turn valves. These components fall into two common categories: (1) passive or friction-based elements, and (2) energetic or dynamically generated elements. Because valve producers can not know the actual piping system parameters when publishing torque values, published torques are typically limited to the five elements of passive or friction-based parts. These embrace:
Passive torque components:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The other 5 parts are impacted by system parameters similar to valve orientation, media and flow velocity. The parts that make up active torque include:
Active torque components:
Disc weight and middle of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When considering all these numerous lively torque elements, it’s potential 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 uncovered to larger service strain and circulate price service circumstances. Since the quarter-turn valve’s closure member is all the time located within the flowing fluid, these higher service situations immediately impact the valve. Operation of these valves require an actuator to rotate and/or hold the closure member within the valve’s physique as it reacts to all of the fluid pressures and fluid move dynamic situations.
In xp2i to the increased service circumstances, the valve sizes are also increasing. The dynamic situations of the flowing fluid have higher impact on the bigger valve sizes. Therefore, the fluid dynamic results become extra essential than static differential strain and friction loads. Valves may be leak and hydrostatically shell examined during fabrication. However, the total fluid circulate situations cannot be replicated before site set up.
Because of the development for elevated valve sizes and increased operating circumstances, it’s more and more essential for the system designer, operator and proprietor of quarter-turn valves to better understand the influence of system and fluid dynamics have on valve choice, building and use.
The AWWA Manual of Standard Practice M forty nine is devoted to the understanding of quarter-turn valves including operating torque requirements, differential stress, move conditions, throttling, cavitation and system installation variations that instantly influence the operation and successful use of quarter-turn valves in waterworks systems.
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 might be devoted to methods of control valve sizing for fluid move, stress management and throttling in waterworks service. This methodology consists of explanations on using stress, move fee and cavitation graphical windows to supply the user a radical image of valve performance over a spread of anticipated system operating situations.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton began his profession as a consulting engineer within the waterworks industry 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 creating organizations, including 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 lively member of each 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 improvement of their quarter-turn valve efficiency prediction methods for the nuclear energy business.

Scroll to Top