Understanding Torque for Quarter-Turn Valves

Valve producers publish torques for his or her products so that actuation and mounting hardware can be correctly selected. However, published torque values often characterize solely the seating or unseating torque for a valve at its rated stress. While these are important values for reference, revealed valve torques do not account for actual installation and working characteristics. In order to find out the actual working torque for valves, it is needed to grasp the parameters of the piping methods into which they’re installed. Factors corresponding to installation orientation, path of flow and fluid velocity of the media all impact the actual operating torque of valves.
Trunnion mounted ball valve operated by a single appearing spring return actuator. Photo credit score: Val-Matic

The American Water Works Association (AWWA) publishes detailed info 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 published in 2001 with torque calculations for butterfly valves, AWWA M49 is currently in its third version. In addition to information on butterfly valves, the current version also contains working torque calculations for other quarter-turn valves together with plug valves and ball valves. Overall, this handbook 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 normal for 3-in. through 72-in. butterfly valves, C504, was printed in 1958 with 25, 50 and 125 psi pressure courses. In 1966 the 50 and one hundred twenty five psi pressure classes had been increased to seventy five and a hundred and fifty psi. The 250 psi pressure class was added in 2000. The 78-in. and bigger butterfly valve normal, C516, was first published in 2010 with 25, 50, 75 and 150 psi pressure classes with the 250 psi class added in 2014. diaphragm seal -performance butterfly valve normal was published in 2018 and includes 275 and 500 psi pressure courses in addition to pushing the fluid circulate 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 commonplace, C507, for 6-in. by way of 48-in. ball valves in one hundred fifty, 250 and 300 psi pressure lessons was printed in 1973. In 2011, measurement range was elevated 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 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 measurement vary was 3 in. by way of 72 in. with a one hundred seventy five

Example butterfly valve differential strain (top) and circulate price control windows (bottom)

pressure class for 3-in. via 12-in. sizes and 150 psi for the 14-in. via 72-in. The later editions (2009 and 2016) haven’t increased the valve sizes or stress classes. The addition of the A velocity designation (8 fps) was added within 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 via 1,500 mm), C522, is underneath improvement. This standard will encompass the identical a hundred and 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 standard.
In general, all the valve sizes, circulate rates and pressures have elevated because the AWWA standard’s inception.

AWWA Manual M49 identifies 10 components that affect working torque for quarter-turn valves. These elements fall into two common categories: (1) passive or friction-based elements, and (2) active or dynamically generated components. Because valve producers cannot know the precise piping system parameters when publishing torque values, printed torques are typically limited to the five parts 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 different 5 parts are impacted by system parameters similar to valve orientation, media and move velocity. The parts that make up active 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 various active torque parts, it is potential for the actual operating torque to exceed the valve manufacturer’s printed torque values.

Although ไดอะแฟรม ซีล -turn valves have been used within the waterworks trade for a century, they are being uncovered to higher service stress and move price service circumstances. Since the quarter-turn valve’s closure member is always situated in the flowing fluid, these larger service situations immediately influence the valve. Operation of those valves require an actuator to rotate and/or hold the closure member inside the valve’s physique as it reacts to all the fluid pressures and fluid flow dynamic circumstances.
In addition to the increased service situations, the valve sizes are also increasing. The dynamic circumstances of the flowing fluid have larger impact on the larger valve sizes. Therefore, the fluid dynamic results turn into extra necessary than static differential pressure and friction loads. Valves may be leak and hydrostatically shell tested throughout fabrication. However, the full fluid circulate situations can’t be replicated before site set up.
Because of the pattern for elevated valve sizes and increased operating conditions, it’s increasingly essential for the system designer, operator and owner of quarter-turn valves to better perceive the influence of system and fluid dynamics have on valve selection, building and use.
The AWWA Manual of Standard Practice M 49 is dedicated to the understanding of quarter-turn valves including working torque requirements, differential strain, flow circumstances, throttling, cavitation and system installation differences that instantly influence the operation and profitable use of quarter-turn valves in waterworks techniques.

The fourth version of M49 is being developed to incorporate the modifications within the quarter-turn valve product requirements and installed system interactions. A new chapter might be dedicated to methods of management valve sizing for fluid circulate, pressure control and throttling in waterworks service. This methodology contains explanations on using pressure, circulate fee and cavitation graphical home windows to supply the consumer an intensive picture of valve performance over a spread of anticipated system working conditions.
Read: New Technologies Solve Severe Cavitation Problems

About the Authors

Steve Dalton started his career as a consulting engineer in the waterworks trade 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 standards growing 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 involved in quarter-turn valve and actuator engineering and design for 50 years and has been an active member of each 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 also worked with the Electric Power Research Institute (EPRI) within the improvement of their quarter-turn valve performance prediction strategies for the nuclear energy business.

Scroll to Top