Understanding Torque for Quarter-Turn Valves

Valve producers publish torques for his or her merchandise so that actuation and mounting hardware may be properly selected. However, published torque values usually represent solely the seating or unseating torque for a valve at its rated strain. While these are necessary values for reference, revealed valve torques don’t account for actual installation and operating characteristics. In order to determine the precise working torque for valves, it is needed to understand the parameters of the piping methods into which they are put in. digital pressure gauge to set up 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 performing 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 seems 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 at present in its third version. In addition to data on butterfly valves, the current edition additionally includes operating torque calculations for different quarter-turn valves together with plug valves and ball valves. Overall, this manual identifies 10 parts of torque that can contribute to a quarter-turn valve’s working 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 125 psi strain classes. In 1966 the 50 and a hundred twenty five psi stress courses 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 a hundred and fifty psi pressure classes 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 in addition to pushing the fluid flow velocities above class B (16 ft per second) to class C (24 feet per second) and sophistication D (35 feet per second).
The first AWWA quarter-turn ball valve standard, C507, for 6-in. by way of 48-in. ball valves in 150, 250 and 300 psi stress lessons was revealed in 1973. In 2011, measurement vary was increased to 6-in. through 60-in. These valves have all the time been designed for 35 ft per second (fps) most fluid velocity. The velocity designation of “D” was added in 2018.
Although pressure gauge (MSS) first issued a product normal for resilient-seated cast-iron eccentric plug valves in 1991, the primary a AWWA quarter-turn valve standard, C517, was not printed till 2005. The 2005 size range was three in. through seventy two in. with a a hundred seventy five

Example butterfly valve differential stress (top) and move rate management home windows (bottom)

strain class for 3-in. through 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. The addition of the A velocity designation (8 fps) was added within 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 by way of 1,500 mm), C522, is under development. This commonplace will embody the same one hundred fifty, 250 and 300 psi stress classes and the identical fluid velocity designation of “D” (maximum 35 feet per second) as the present C507 ball valve normal.
In common, all of the valve sizes, move rates and pressures have increased because the AWWA standard’s inception.

AWWA Manual M49 identifies 10 elements that have an effect on operating torque for quarter-turn valves. pressure gauge octa fall into two general classes: (1) passive or friction-based elements, and (2) active or dynamically generated elements. Because valve producers can’t know the actual piping system parameters when publishing torque values, published torques are typically limited to the 5 components of passive or friction-based components. These embody:
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 move velocity. The components that make up active torque embrace:
Active torque components:
Disc weight and heart of gravity torque

Disc buoyancy torque

Eccentricity torque

Fluid dynamic torque

Hydrostatic unbalance torque

When contemplating all these various lively torque components, it is attainable for the precise working 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 uncovered to larger service pressure and flow rate service conditions. Since the quarter-turn valve’s closure member is all the time situated within the flowing fluid, these greater service circumstances immediately impression the valve. Operation of those valves require an actuator to rotate and/or hold the closure member within the valve’s body because it reacts to all the fluid pressures and fluid circulate dynamic conditions.
In addition to the elevated service situations, the valve sizes are additionally rising. The dynamic situations of the flowing fluid have higher impact on the larger valve sizes. Therefore, the fluid dynamic effects turn into extra important than static differential pressure and friction masses. Valves may be leak and hydrostatically shell tested during fabrication. However, the total fluid flow circumstances cannot be replicated before site set up.
Because of the pattern for elevated valve sizes and elevated working circumstances, it is increasingly necessary for the system designer, operator and proprietor of quarter-turn valves to raised understand the impact of system and fluid dynamics have on valve choice, construction and use.
The AWWA Manual of Standard Practice M forty nine is dedicated to the understanding of quarter-turn valves including working torque necessities, differential strain, circulate situations, throttling, cavitation and system set up differences that directly affect the operation and profitable use of quarter-turn valves in waterworks techniques.

The fourth version 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 devoted to strategies of control valve sizing for fluid move, stress management and throttling in waterworks service. This methodology consists of explanations on the usage of pressure, circulate price and cavitation graphical home windows to provide the consumer a thorough picture of valve efficiency over a spread 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 beforehand labored 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 energetic 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 additionally labored with the Electric Power Research Institute (EPRI) in the growth of their quarter-turn valve performance prediction methods for the nuclear power trade.

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