Valve producers publish torques for his or her merchandise so that actuation and mounting hardware can be properly chosen. However, printed torque values often characterize solely the seating or unseating torque for a valve at its rated strain. While these are essential values for reference, published valve torques do not account for precise installation and operating characteristics. In order to find out the precise working torque for valves, it’s necessary to grasp the parameters of the piping methods into which they are installed. Factors similar to set up orientation, direction of move and fluid velocity of the media all influence the precise operating torque of valves.
Trunnion mounted ball valve operated by a single performing spring return actuator. Photo credit: Val-Matic

The American Water Works Association (AWWA) publishes detailed info 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 revealed in 2001 with torque calculations for butterfly valves, AWWA M49 is currently in its third version. In addition to information on butterfly valves, the present edition also consists of working torque calculations for different quarter-turn valves including plug valves and ball valves. Overall, this manual identifies 10 elements 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. by way of 72-in. butterfly valves, C504, was printed in 1958 with 25, 50 and 125 psi stress courses. In 1966 the 50 and 125 psi stress lessons had been increased to seventy five and 150 psi. The 250 psi strain class was added in 2000. The 78-in. and larger butterfly valve commonplace, C516, was first published in 2010 with 25, 50, seventy five and one hundred fifty psi strain lessons with the 250 psi class added in 2014. The high-performance butterfly valve standard was revealed in 2018 and consists of 275 and 500 psi strain classes as nicely as pushing the fluid circulate velocities above class B (16 toes per second) to class C (24 feet per second) and class D (35 feet per second).
The first AWWA quarter-turn ball valve normal, C507, for 6-in. via 48-in. ball valves in a hundred and fifty, 250 and 300 psi strain classes was revealed in 1973. In 2011, measurement range was elevated to 6-in. through 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 standard for resilient-seated cast-iron eccentric plug valves in 1991, the first a AWWA quarter-turn valve standard, C517, was not printed till 2005. The 2005 dimension range was 3 in. through seventy two in. with a a hundred seventy five

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

pressure class for 3-in. by way of 12-in. sizes and 150 psi for the 14-in. through 72-in. The later editions (2009 and 2016) have not elevated 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 decrease values.
The want for a rotary cone valve was recognized in 2018 and the AWWA Rotary Cone Valves, 6 Inch Through 60 Inch (150 mm by way of 1,500 mm), C522, is under growth. This standard will embody the identical a hundred and fifty, 250 and 300 psi pressure classes and the same fluid velocity designation of “D” (maximum 35 feet per second) as the present C507 ball valve normal.
In basic, all of the valve sizes, flow rates and pressures have increased 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 basic classes: (1) passive or friction-based elements, and (2) energetic or dynamically generated components. Because valve manufacturers cannot know the precise piping system parameters when publishing torque values, published torques are generally restricted to the 5 components of passive or friction-based elements. These embody:
Passive torque parts:
Seating friction torque

Packing friction torque

Hub seal friction torque

Bearing friction torque

Thrust bearing friction torque

The other five elements are impacted by system parameters similar to valve orientation, media and circulate velocity. The elements that make up lively torque include:
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 energetic torque components, it’s possible for the actual working torque to exceed the valve manufacturer’s published torque values.

Although quarter-turn valves have been used in the waterworks industry for a century, they’re being uncovered to greater service pressure and circulate price service conditions. Since the quarter-turn valve’s closure member is at all times located within the flowing fluid, these greater service circumstances instantly impact the valve. Operation of these 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 increased service situations, the valve sizes are also increasing. The dynamic circumstances of the flowing fluid have greater effect on the bigger valve sizes. Therefore, the fluid dynamic results turn into extra essential than static differential stress and friction hundreds. Valves can be leak and hydrostatically shell examined throughout fabrication. However, the complete fluid move situations cannot be replicated earlier than site installation.
Because of the pattern for increased valve sizes and elevated operating circumstances, it’s increasingly essential for the system designer, operator and proprietor of quarter-turn valves to raised understand the influence of system and fluid dynamics have on valve selection, development and use.
The AWWA Manual of Standard Practice M 49 is devoted to the understanding of quarter-turn valves together with working torque requirements, differential strain, move circumstances, throttling, cavitation and system installation differences that instantly influence the operation and profitable use of quarter-turn valves in waterworks systems.

The fourth edition of M49 is being developed to include the adjustments in the quarter-turn valve product requirements and put in system interactions. A new chapter shall be dedicated to strategies of management valve sizing for fluid move, stress control and throttling in waterworks service. This methodology includes explanations on the utilization of stress, flow price and cavitation graphical home windows to supply the person an intensive picture of valve performance over a range of anticipated system operating circumstances.
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About the Authors

Steve Dalton started his profession as a consulting engineer in the waterworks industry 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 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 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 labored with the Electric Power Research Institute (EPRI) within the improvement of their quarter-turn valve efficiency prediction methods for the nuclear power business.