Valve producers publish torques for his or her merchandise so that actuation and mounting hardware can be properly selected. However, revealed 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 do not account for actual installation and operating traits. In order to find out the actual operating torque for valves, it’s necessary to grasp the parameters of the piping techniques into which they are put in. Factors similar to installation orientation, direction of circulate and fluid velocity of the media all influence the precise operating 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 data on calculating working torques for quarter-turn valves. This data 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 currently in its third edition. In addition to information on butterfly valves, the present edition also consists of operating torque calculations for different quarter-turn valves together with plug valves and ball valves. Overall, this guide 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 standard for 3-in. via 72-in. butterfly valves, C504, was published in 1958 with 25, 50 and a hundred twenty five psi stress lessons. In 1966 the 50 and a hundred twenty five psi pressure lessons were elevated to seventy five and one hundred 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, seventy five and 150 psi strain courses with the 250 psi class added in 2014. The high-performance butterfly valve normal was revealed in 2018 and contains 275 and 500 psi stress courses in addition to pushing the fluid flow velocities above class B (16 feet per second) to class C (24 toes 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 a hundred and fifty, 250 and 300 psi strain lessons was published in 1973. In 2011, size range was increased to 6-in. through 60-in. These valves have always 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 primary a AWWA quarter-turn valve normal, C517, was not published until 2005. The 2005 size vary was 3 in. by way of seventy two in. with a one hundred seventy five

Example butterfly valve differential stress (top) and circulate price control 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 elevated the valve sizes or stress courses. 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 decrease values.
diaphragm seal 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 improvement. This commonplace will encompass the identical a hundred and fifty, 250 and 300 psi stress lessons and the identical fluid velocity designation of “D” (maximum 35 toes per second) as the current C507 ball valve commonplace.
In general, all the valve sizes, move rates and pressures have increased for the reason that 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 general classes: (1) passive or friction-based components, and (2) lively or dynamically generated elements. Because valve manufacturers can not know the actual piping system parameters when publishing torque values, published torques are generally limited to the 5 components 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 parts are impacted by system parameters such as valve orientation, media and move velocity. The components that make up active torque embrace:
Active torque elements:
Disc weight and middle of gravity torque

Disc buoyancy torque

Eccentricity torque

Fluid dynamic torque

Hydrostatic unbalance torque

When considering all these varied lively torque parts, it is possible for the precise operating torque to exceed the valve manufacturer’s revealed torque values.

Although quarter-turn valves have been used within the waterworks industry for a century, they are being exposed to greater service pressure and circulate price service conditions. Since the quarter-turn valve’s closure member is all the time situated in the flowing fluid, these higher service circumstances instantly influence the valve. Operation of these valves require an actuator to rotate and/or hold the closure member inside the valve’s physique because it reacts to all the fluid pressures and fluid flow dynamic circumstances.
In addition to the elevated service conditions, the valve sizes are also rising. The dynamic circumstances of the flowing fluid have higher impact on the bigger valve sizes. Therefore, the fluid dynamic effects become more important than static differential pressure and friction masses. Valves can be leak and hydrostatically shell tested throughout fabrication. However, the total fluid move situations cannot be replicated earlier than site installation.
Because of the pattern for elevated valve sizes and elevated working situations, it’s increasingly necessary for the system designer, operator and owner 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 forty nine is devoted to the understanding of quarter-turn valves together with working torque requirements, differential strain, flow circumstances, throttling, cavitation and system set up differences that directly influence the operation and profitable use of quarter-turn valves in waterworks systems.

The fourth edition of M49 is being developed to incorporate the modifications in the quarter-turn valve product requirements and installed system interactions. A new chapter shall be devoted to methods of control valve sizing for fluid flow, pressure control and throttling in waterworks service. This methodology contains explanations on the utilization of pressure, circulate price and cavitation graphical windows to supply the person an intensive picture of valve performance over a variety of anticipated system operating circumstances.
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 worked at Val-Matic as Director of Engineering. He has participated in standards growing organizations, together with 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 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.” He has additionally labored with the Electric Power Research Institute (EPRI) in the growth of their quarter-turn valve efficiency prediction strategies for the nuclear energy trade.