Understanding Torque for Quarter-Turn Valves

Valve producers publish torques for their merchandise in order that actuation and mounting hardware can be properly selected. However, revealed torque values often represent only the seating or unseating torque for a valve at its rated pressure. While these are essential values for reference, printed valve torques don’t account for actual set up and operating traits. In order to determine the actual operating torque for valves, it is needed to know the parameters of the piping systems into which they are 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 appearing spring return actuator. Photo credit: Val-Matic

The American Water Works Association (AWWA) publishes detailed data on calculating operating torques for quarter-turn valves. This data seems 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 present edition also consists of working torque calculations for other quarter-turn valves including plug valves and ball valves. Overall, this handbook identifies 10 components of torque that may contribute to a quarter-turn valve’s working torque.
Example torque calculation abstract graph


The first AWWA quarter-turn valve standard for 3-in. through 72-in. butterfly valves, C504, was revealed in 1958 with 25, 50 and one hundred twenty five psi stress classes. In 1966 the 50 and 125 psi pressure classes were increased to seventy five 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 pressure classes with the 250 psi class added in 2014. The high-performance butterfly valve commonplace was published in 2018 and includes 275 and 500 psi strain courses as nicely as pushing the fluid circulate velocities above class B (16 toes per second) to class C (24 ft per second) and class D (35 ft per second).
The first AWWA quarter-turn ball valve commonplace, C507, for 6-in. via 48-in. ball valves in 150, 250 and 300 psi pressure classes was published in 1973. In 2011, dimension vary was increased to 6-in. via 60-in. These valves have at all times 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 standard for resilient-seated cast-iron eccentric plug valves in 1991, the first a AWWA quarter-turn valve commonplace, C517, was not printed till 2005. The 2005 dimension vary was 3 in. by way of seventy two in. with a a hundred seventy five

Example butterfly valve differential pressure (top) and circulate fee control windows (bottom)

stress class for 3-in. by way of 12-in. sizes and a hundred and fifty psi for the 14-in. via 72-in. The later editions (2009 and 2016) haven’t elevated the valve sizes or strain courses. The addition of the A velocity designation (8 fps) was added in the 2017 version. 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 beneath development. This normal will embody the same one hundred fifty, 250 and 300 psi stress classes 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, circulate rates and pressures have elevated since the AWWA standard’s inception.

AWWA Manual M49 identifies 10 elements that have an effect on working torque for quarter-turn valves. These elements fall into two general classes: (1) passive or friction-based elements, and (2) lively or dynamically generated elements. Because valve producers can’t know the precise piping system parameters when publishing torque values, published torques are typically limited to the 5 parts of passive or friction-based parts. These embody:
Passive torque components:
Seating friction torque

Packing friction torque

Hub seal friction torque

Bearing friction torque

Thrust bearing friction torque

The different five parts are impacted by system parameters such as valve orientation, media and circulate velocity. The components that make up lively torque embrace:
Active torque parts:
Disc weight and heart of gravity torque

Disc buoyancy torque

Eccentricity torque

Fluid dynamic torque

Hydrostatic unbalance torque

When considering all these varied active torque elements, it’s possible for the precise 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 are being exposed to higher service strain and circulate fee service situations. Since the quarter-turn valve’s closure member is at all times positioned in the flowing fluid, these larger service situations immediately impression the valve. Operation of those valves require an actuator to rotate and/or maintain the closure member within the valve’s body because it reacts to all of the fluid pressures and fluid move dynamic conditions.
In addition to the elevated service conditions, the valve sizes are additionally rising. The dynamic circumstances of the flowing fluid have larger impact on the larger valve sizes. Therefore, the fluid dynamic effects turn into extra essential than static differential stress and friction masses. Valves can be leak and hydrostatically shell tested throughout fabrication. However, the total fluid move conditions can’t be replicated before web site set up.
Because of the trend for increased valve sizes and increased operating situations, it is increasingly necessary for the system designer, operator and owner of quarter-turn valves to better perceive the impression of system and fluid dynamics have on valve choice, building and use.
The AWWA Manual of Standard Practice M forty nine is dedicated to the understanding of quarter-turn valves including operating torque necessities, differential pressure, circulate circumstances, throttling, cavitation and system set up variations that immediately influence the operation and successful use of quarter-turn valves in waterworks techniques.

The fourth version of M49 is being developed to include the modifications in the quarter-turn valve product standards and installed system interactions. A new chapter will be dedicated to methods of control valve sizing for fluid circulate, pressure control and throttling in waterworks service. This methodology contains explanations on the usage of strain, move fee and cavitation graphical home windows to supply the consumer an intensive image of valve efficiency over a spread of anticipated system working situations.
Read: New Technologies Solve Severe Cavitation Problems

About the Authors

Steve Dalton started his profession 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 requirements developing organizations, together with AWWA, MSS, ASSE and API. Dalton holds BS and MS levels 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 energetic 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.” pressure gauge octa has additionally worked with the Electric Power Research Institute (EPRI) in the development of their quarter-turn valve performance prediction methods for the nuclear power trade.