Understanding Torque for Quarter-Turn Valves

Valve producers publish torques for his or her products in order that actuation and mounting hardware can be correctly selected. However, revealed torque values typically represent solely the seating or unseating torque for a valve at its rated strain. While these are important values for reference, printed valve torques don’t account for actual installation and working traits. In order to determine the precise operating torque for valves, it’s essential to understand the parameters of the piping methods into which they are installed. Factors such as installation orientation, path of move 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 information on calculating working torques for quarter-turn valves. This information appears in AWWA Manual M49 Quarter-Turn Valves: Head Loss, Torque, and Cavitation Analysis. Originally published in Safety with torque calculations for butterfly valves, AWWA M49 is currently in its third version. In addition to information on butterfly valves, the current edition additionally contains 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 normal for 3-in. via 72-in. butterfly valves, C504, was revealed in 1958 with 25, 50 and 125 psi stress classes. In 1966 the 50 and a hundred twenty five psi stress courses were increased to 75 and a hundred and fifty psi. The 250 psi stress class was added in 2000. The 78-in. and larger butterfly valve normal, C516, was first printed in 2010 with 25, 50, 75 and 150 psi pressure classes with the 250 psi class added in 2014. The high-performance butterfly valve standard was published in 2018 and includes 275 and 500 psi pressure classes in addition to pushing the fluid circulate velocities above class B (16 ft 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 150, 250 and 300 psi stress lessons was published in 1973. In 2011, dimension vary was increased to 6-in. by way of 60-in. These valves have all the time 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 standard, C517, was not published until 2005. The 2005 measurement range was 3 in. by way of seventy two in. with a 175
Example butterfly valve differential stress (top) and move price control 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) haven’t 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 used in wastewater service where pressures and fluid velocities are maintained at lower 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 commonplace will embody the identical a hundred and fifty, 250 and 300 psi strain classes and the identical fluid velocity designation of “D” (maximum 35 toes per second) as the current C507 ball valve commonplace.
In general, all of the valve sizes, move rates and pressures have increased because the AWWA standard’s inception.
AWWA Manual M49 identifies 10 components that affect operating torque for quarter-turn valves. These parts fall into two common classes: (1) passive or friction-based components, and (2) energetic or dynamically generated parts. Because valve manufacturers cannot know the precise piping system parameters when publishing torque values, published torques are generally limited to the five elements of passive or friction-based parts. These embrace:
Passive torque elements:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The other 5 components are impacted by system parameters corresponding to valve orientation, media and circulate velocity. The components that make up active torque include:
Active torque elements:
Disc weight and middle of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When contemplating all these numerous active torque elements, it is attainable for the actual working torque to exceed the valve manufacturer’s published torque values.
Although quarter-turn valves have been used in the waterworks business for a century, they’re being uncovered to larger service strain and move fee service circumstances. Since the quarter-turn valve’s closure member is at all times located in the flowing fluid, these higher service conditions immediately influence the valve. Operation of these valves require an actuator to rotate and/or hold the closure member throughout the valve’s physique because it reacts to all of the fluid pressures and fluid flow dynamic conditions.
In addition to the increased service situations, the valve sizes are also rising. The dynamic circumstances of the flowing fluid have higher impact on the larger valve sizes. Therefore, the fluid dynamic results turn into extra essential than static differential pressure and friction masses. Valves can be leak and hydrostatically shell examined throughout fabrication. However, the full fluid circulate conditions can’t be replicated before website installation.
Because of the trend for increased valve sizes and elevated working conditions, it’s increasingly necessary for the system designer, operator and proprietor of quarter-turn valves to higher perceive the impression of system and fluid dynamics have on valve selection, construction and use.
The AWWA Manual of Standard Practice M forty nine is dedicated to the understanding of quarter-turn valves together with operating torque necessities, differential strain, move conditions, throttling, cavitation and system set up variations that immediately 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 within the quarter-turn valve product standards and installed system interactions. A new chapter shall be devoted to strategies of management valve sizing for fluid circulate, pressure control and throttling in waterworks service. This methodology includes explanations on using pressure, circulate rate and cavitation graphical windows to supply the consumer an intensive picture of valve efficiency over a range of anticipated system operating circumstances.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton started his profession as a consulting engineer within 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 beforehand worked at Val-Matic as Director of Engineering. He has participated in requirements 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 concerned 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.” He has additionally labored with the Electric Power Research Institute (EPRI) within the growth of their quarter-turn valve performance prediction methods for the nuclear power business.

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