Understanding Torque for Quarter-Turn Valves

Valve producers publish torques for his or her products in order that actuation and mounting hardware may be properly selected. However, published torque values usually represent only the seating or unseating torque for a valve at its rated stress. While these are essential values for reference, printed valve torques do not account for actual installation and operating traits. In order to determine the actual working torque for valves, it is necessary to know the parameters of the piping methods into which they’re put in. Factors similar to set up orientation, path of move and fluid velocity of the media all influence the precise operating torque of valves.
Trunnion mounted ball valve operated by a single appearing spring return actuator. Photo credit: Val-Matic

The American Water Works Association (AWWA) publishes detailed data 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 published in 2001 with torque calculations for butterfly valves, AWWA M49 is presently in its third edition. In addition to data on butterfly valves, the current version also includes working torque calculations for other quarter-turn valves together with plug valves and ball valves. Overall, this guide identifies 10 components of torque that can contribute to a quarter-turn valve’s operating torque.
Example torque calculation abstract graph


The first AWWA quarter-turn valve normal for 3-in. through 72-in. butterfly valves, C504, was revealed in 1958 with 25, 50 and one hundred twenty five psi strain classes. In 1966 the 50 and one hundred twenty five psi stress courses have been increased to 75 and 150 psi. The 250 psi pressure class was added in 2000. The 78-in. and larger butterfly valve standard, C516, was first revealed in 2010 with 25, 50, seventy five and 150 psi pressure classes with the 250 psi class added in 2014. The high-performance butterfly valve standard was printed in 2018 and contains 275 and 500 psi stress lessons as well as pushing the fluid move velocities above class B (16 ft per second) to class C (24 feet per second) and sophistication D (35 toes per second).
The first AWWA quarter-turn ball valve commonplace, C507, for 6-in. by way of 48-in. ball valves in a hundred and fifty, 250 and 300 psi stress classes was revealed in 1973. In 2011, size vary was elevated to 6-in. via 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 commonplace for resilient-seated cast-iron eccentric plug valves in 1991, the first a AWWA quarter-turn valve commonplace, C517, was not published till 2005. The 2005 size range was 3 in. via 72 in. with a one hundred seventy five

Example butterfly valve differential strain (top) and flow price management home windows (bottom)

pressure class for 3-in. through 12-in. sizes and one hundred fifty psi for the 14-in. through 72-in. The later editions (2009 and 2016) haven’t increased the valve sizes or strain courses. The addition of the A velocity designation (8 fps) was added within the 2017 edition. This valve is primarily utilized 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 underneath development. This commonplace will encompass the same one hundred fifty, 250 and 300 psi strain courses and the same fluid velocity designation of “D” (maximum 35 toes per second) as the present C507 ball valve standard.
In general, all of the valve sizes, move rates and pressures have increased for the reason that AWWA standard’s inception.

AWWA Manual M49 identifies 10 components that have an effect on working torque for quarter-turn valves. These parts fall into two basic classes: (1) passive or friction-based components, and (2) energetic or dynamically generated elements. Because valve manufacturers can not know the precise piping system parameters when publishing torque values, printed torques are generally restricted to the 5 components of passive or friction-based components. These include:
Passive torque elements:
Seating friction torque

Packing friction torque

Hub seal friction torque

Bearing friction torque

Thrust bearing friction torque

The other 5 components are impacted by system parameters similar to valve orientation, media and flow velocity. The components that make up energetic torque embody:
Active torque parts:
Disc weight and center of gravity torque

Disc buoyancy torque

Eccentricity torque

Fluid dynamic torque

Hydrostatic unbalance torque

When considering all these numerous active torque components, it is potential for the precise operating torque to exceed the valve manufacturer’s published torque values.

Although quarter-turn valves have been used within the waterworks industry for a century, they’re being uncovered to greater service strain and flow price service circumstances. Since the quarter-turn valve’s closure member is at all times situated in the flowing fluid, these greater service situations immediately impression the valve. Operation of those valves require an actuator to rotate and/or hold the closure member within the valve’s physique because it reacts to all of the fluid pressures and fluid flow dynamic circumstances.
In addition to the elevated service conditions, the valve sizes are also rising. The dynamic conditions of the flowing fluid have higher effect on the larger valve sizes. Therefore, the fluid dynamic effects become extra important than static differential strain and friction loads. Valves can be leak and hydrostatically shell examined throughout fabrication. However, the total fluid circulate circumstances cannot be replicated before site set up.
Because of the trend for increased valve sizes and elevated operating circumstances, it is increasingly necessary for the system designer, operator and owner of quarter-turn valves to raised understand the impact 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 working torque necessities, differential stress, flow circumstances, throttling, cavitation and system set up variations that directly influence the operation and successful use of quarter-turn valves in waterworks methods.

The fourth edition of M49 is being developed to include the modifications in the quarter-turn valve product standards and put in system interactions. A new chapter might be dedicated to methods of control valve sizing for fluid flow, pressure control and throttling in waterworks service. This methodology consists of explanations on using pressure, flow price and cavitation graphical home windows to supply the person a radical image of valve performance over a range of anticipated system operating conditions.
Read: New Technologies Solve Severe Cavitation Problems

About the Authors

Steve Dalton started 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 beforehand worked at Val-Matic as Director of Engineering. He has participated in requirements 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 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 labored with the Electric Power Research Institute (EPRI) in the growth of their quarter-turn valve performance prediction methods for the nuclear power industry.

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