Understanding Torque for Quarter-Turn Valves

Valve manufacturers publish torques for their merchandise in order that actuation and mounting hardware can be correctly chosen. However, revealed torque values typically symbolize solely the seating or unseating torque for a valve at its rated stress. While these are necessary values for reference, printed valve torques don’t account for actual installation and working characteristics. In order to determine the actual operating torque for valves, it is needed to grasp the parameters of the piping techniques into which they are put in. Factors corresponding to set up orientation, course of flow and fluid velocity of the media all impact 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 info on calculating operating 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 info on butterfly valves, the current edition also consists of working torque calculations for other 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 standard for 3-in. via 72-in. butterfly valves, C504, was published in 1958 with 25, 50 and 125 psi stress courses. In 1966 the 50 and 125 psi pressure courses have been elevated to seventy five and 150 psi. The 250 psi stress class was added in 2000. The 78-in. and bigger butterfly valve standard, C516, was first published in 2010 with 25, 50, seventy five and 150 psi stress lessons with the 250 psi class added in 2014. The high-performance butterfly valve standard was revealed in 2018 and contains 275 and 500 psi strain courses as well as pushing the fluid move velocities above class B (16 feet per second) to class C (24 toes per second) and sophistication D (35 toes per second).
The first AWWA quarter-turn ball valve normal, C507, for 6-in. through 48-in. ball valves in one hundred fifty, 250 and 300 psi stress lessons was printed in 1973. In 2011, dimension range was elevated 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 standard 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 dimension vary was 3 in. by way of seventy two in. with a one hundred seventy five

Example butterfly valve differential stress (top) and circulate rate control home windows (bottom)

pressure class for 3-in. by way of 12-in. sizes and one hundred fifty psi for the 14-in. through 72-in. The later editions (2009 and 2016) have not elevated the valve sizes or strain courses. The addition of the A velocity designation (8 fps) was added in the 2017 edition. This valve is primarily used in wastewater service the place 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 via 1,500 mm), C522, is underneath improvement. This standard will embody the identical one hundred fifty, 250 and 300 psi strain classes and the identical fluid velocity designation of “D” (maximum 35 feet per second) as the current C507 ball valve standard.
In general, all of the valve sizes, move rates and pressures have elevated since the AWWA standard’s inception.

AWWA Manual M49 identifies 10 parts that have an result on operating torque for quarter-turn valves. These parts fall into two general categories: (1) passive or friction-based parts, and (2) energetic or dynamically generated parts. Because valve producers cannot know the precise piping system parameters when publishing torque values, revealed torques are usually limited to the five elements 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 other five components are impacted by system parameters similar to valve orientation, media and flow velocity. The elements that make up energetic torque embody:
Active torque components:
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 elements, it’s possible for the actual working torque to exceed the valve manufacturer’s printed torque values.

Although quarter-turn valves have been used in the waterworks trade for a century, they are being exposed to larger service strain and circulate rate service situations. Since the quarter-turn valve’s closure member is at all times located within the flowing fluid, these greater service conditions immediately influence the valve. Operation of these valves require an actuator to rotate and/or maintain the closure member inside the valve’s physique because it reacts to all the fluid pressures and fluid circulate dynamic circumstances.
In addition to the increased service conditions, the valve sizes are additionally increasing. ไดอะแฟรม ซีล of the flowing fluid have higher impact on the bigger valve sizes. Therefore, the fluid dynamic effects turn out to be more important than static differential stress and friction loads. Valves may be leak and hydrostatically shell tested throughout fabrication. However, the total fluid circulate situations cannot be replicated earlier than web site installation.
Because of the trend for elevated valve sizes and increased working conditions, it is more and more important for the system designer, operator and proprietor of quarter-turn valves to better perceive the influence of system and fluid dynamics have on valve choice, building 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 stress, circulate situations, throttling, cavitation and system set up variations that instantly 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 within the quarter-turn valve product requirements and installed system interactions. A new chapter will be devoted to strategies of management valve sizing for fluid flow, strain control and throttling in waterworks service. This methodology includes explanations on using pressure, circulate price and cavitation graphical windows to offer the consumer a radical image 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 profession as a consulting engineer within 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 previously labored at Val-Matic as Director of Engineering. He has participated in standards creating organizations, including 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 involved in quarter-turn valve and actuator engineering and design for 50 years and has been an lively 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 labored with the Electric Power Research Institute (EPRI) within the growth of their quarter-turn valve performance prediction strategies for the nuclear power trade.

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