Understanding Torque for Quarter-Turn Valves

Valve producers publish torques for their products so that actuation and mounting hardware could be properly chosen. However, published torque values often symbolize 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 actual set up and working characteristics. In order to discover out the precise operating torque for valves, it’s necessary to grasp the parameters of the piping techniques into which they are installed. Factors corresponding to set up orientation, path of move and fluid velocity of the media all impact the precise 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 info on calculating operating torques for quarter-turn valves. This info 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 at present in its third edition. In addition to information on butterfly valves, the current edition also consists of operating torque calculations for other quarter-turn valves including plug valves and ball valves. Overall, this guide 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. by way of 72-in. butterfly valves, C504, was published in 1958 with 25, 50 and 125 psi strain classes. In 1966 the 50 and 125 psi stress lessons have been elevated to 75 and 150 psi. The 250 psi strain class was added in 2000. The 78-in. and bigger butterfly valve standard, C516, was first printed in 2010 with 25, 50, seventy five and one hundred fifty psi stress courses with the 250 psi class added in 2014. The high-performance butterfly valve standard was published in 2018 and includes 275 and 500 psi stress classes as properly as pushing the fluid circulate 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 standard, C507, for 6-in. via 48-in. ball valves in one hundred fifty, 250 and 300 psi strain courses was published in 1973. In 2011, dimension 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 normal for resilient-seated cast-iron eccentric plug valves in 1991, the first a AWWA quarter-turn valve normal, C517, was not printed until 2005. The 2005 dimension vary was three in. by way of seventy two in. with a 175

Example butterfly valve differential stress (top) and flow rate control windows (bottom)

stress class for 3-in. via 12-in. sizes and a hundred and fifty psi for the 14-in. through 72-in. The later editions (2009 and 2016) have not increased the valve sizes or strain courses. The addition of the A velocity designation (8 fps) was added in the 2017 edition. This valve is primarily utilized in wastewater service where pressures and fluid velocities are maintained at decrease values.
The need 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 growth. This commonplace will encompass the same a hundred and fifty, 250 and 300 psi stress lessons and the same fluid velocity designation of “D” (maximum 35 toes per second) as the present C507 ball valve normal.
In general, all the valve sizes, move charges and pressures have increased because the AWWA standard’s inception.

AWWA Manual M49 identifies 10 parts that have an result on operating torque for quarter-turn valves. These components fall into two basic classes: (1) passive or friction-based parts, and (2) active or dynamically generated components. Because valve producers can’t know the actual piping system parameters when publishing torque values, printed torques are generally limited to the five elements of passive or friction-based parts. These embrace:
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 such as valve orientation, media and flow velocity. The components that make up energetic torque include:
Active torque components:
Disc weight and center of gravity torque

Disc buoyancy torque

Eccentricity torque

Fluid dynamic torque

Hydrostatic unbalance torque

When considering all these various energetic torque parts, it’s possible for the actual operating torque to exceed the valve manufacturer’s published torque values.

Although quarter-turn valves have been used within the waterworks business for a century, they’re being exposed to higher service stress and move price service circumstances. Since the quarter-turn valve’s closure member is at all times positioned within the flowing fluid, these higher service conditions directly influence the valve. Operation of those 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 move dynamic circumstances.
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 bigger valve sizes. Therefore, the fluid dynamic results turn out to be more necessary than static differential stress and friction masses. Valves may be leak and hydrostatically shell examined throughout fabrication. However, the complete fluid circulate situations can’t be replicated before site installation.
Because of the pattern for elevated valve sizes and increased operating conditions, it is increasingly essential for the system designer, operator and proprietor of quarter-turn valves to better understand the impression of system and fluid dynamics have on valve choice, building and use.
The AWWA Manual of Standard Practice M 49 is devoted to the understanding of quarter-turn valves including operating torque necessities, differential pressure, circulate conditions, throttling, cavitation and system installation variations that immediately affect the operation and profitable use of quarter-turn valves in waterworks techniques.
AWWA MANUAL OF STANDARD PRACTICE M49 4TH EDITION pressure gauge of M49 is being developed to incorporate the adjustments within the quarter-turn valve product standards and put in system interactions. A new chapter might be dedicated to strategies of control valve sizing for fluid flow, strain management and throttling in waterworks service. This methodology consists of explanations on the usage of strain, flow price and cavitation graphical windows to supply the user an intensive picture of valve efficiency over a variety of anticipated system operating situations.
Read: New Technologies Solve Severe Cavitation Problems

About the Authors

Steve Dalton began his career as a consulting engineer in 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 worked at Val-Matic as Director of Engineering. He has participated in standards growing 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 improvement of their quarter-turn valve efficiency prediction strategies for the nuclear energy business.

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