Understanding Torque for Quarter-Turn Valves

Valve producers publish torques for their products in order that actuation and mounting hardware could be properly selected. However, printed torque values often symbolize solely the seating or unseating torque for a valve at its rated pressure. While these are important values for reference, published valve torques don’t account for precise set up and working characteristics. In order to determine the precise working torque for valves, it’s needed to know the parameters of the piping methods into which they are installed. Factors similar to installation orientation, course of move and fluid velocity of the media all influence the precise working 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 information 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 at present in its third version. In addition to data on butterfly valves, the present edition additionally contains working torque calculations for other quarter-turn valves including plug valves and ball valves. Overall, this guide identifies 10 elements of torque that can contribute to a quarter-turn valve’s operating torque.
Example torque calculation abstract graph
The first AWWA quarter-turn valve commonplace for 3-in. through 72-in. butterfly valves, C504, was revealed in 1958 with 25, 50 and a hundred twenty five psi strain lessons. In 1966 the 50 and one hundred twenty five psi strain classes had been elevated to seventy five and one hundred fifty psi. The 250 psi stress class was added in 2000. The 78-in. and bigger butterfly valve normal, C516, was first printed in 2010 with 25, 50, seventy five and a hundred and fifty psi pressure classes with the 250 psi class added in 2014. The high-performance butterfly valve standard was printed in 2018 and contains 275 and 500 psi stress classes as nicely as pushing the fluid move velocities above class B (16 feet per second) to class C (24 feet 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 150, 250 and 300 psi stress courses was revealed in 1973. In 2011, size vary was elevated to 6-in. by way of 60-in. These valves have always 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 standard, C517, was not printed till 2005. The 2005 measurement vary was 3 in. through seventy two in. with a a hundred seventy five
Example butterfly valve differential pressure (top) and flow rate control windows (bottom)
strain class for 3-in. via 12-in. sizes and one hundred fifty psi for the 14-in. via 72-in. The later editions (2009 and 2016) have not elevated the valve sizes or pressure classes. The addition of the A velocity designation (8 fps) was added within the 2017 edition. This valve is primarily utilized in wastewater service the place pressures and fluid velocities are maintained at lower values.
The want 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 underneath improvement. This commonplace will encompass the same one hundred fifty, 250 and 300 psi pressure lessons and the same fluid velocity designation of “D” (maximum 35 toes per second) as the present C507 ball valve standard.
In general, all the valve sizes, move rates and pressures have increased because the AWWA standard’s inception.
AWWA Manual M49 identifies 10 components that have an result on operating torque for quarter-turn valves. These elements fall into two basic classes: (1) passive or friction-based elements, and (2) lively or dynamically generated components. Because valve manufacturers can not know the actual piping system parameters when publishing torque values, revealed torques are usually restricted to the 5 components of passive or friction-based components. These embody:
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 corresponding to valve orientation, media and flow velocity. The parts that make up energetic torque embody:
Active torque elements:
Disc weight and center of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When considering all these numerous lively torque components, it’s possible for the actual operating torque to exceed the valve manufacturer’s revealed torque values.
Although quarter-turn valves have been used within the waterworks trade for a century, they’re being exposed to higher service pressure and circulate fee service situations. Since the quarter-turn valve’s closure member is all the time situated within the flowing fluid, these larger service situations immediately influence the valve. Operation of these valves require an actuator to rotate and/or hold the closure member within the valve’s physique as it reacts to all of the fluid pressures and fluid circulate dynamic circumstances.
In addition to the elevated service circumstances, the valve sizes are additionally growing. The dynamic situations of the flowing fluid have larger impact on the bigger valve sizes. Therefore, the fluid dynamic results turn out to be extra necessary than static differential strain and friction loads. Valves could be leak and hydrostatically shell tested during fabrication. However, the total fluid circulate circumstances can’t be replicated before website set up.
Because of the trend for elevated valve sizes and increased operating conditions, it is more and more necessary for the system designer, operator and owner of quarter-turn valves to higher understand the impact 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 including operating torque necessities, differential pressure, circulate conditions, throttling, cavitation and system installation variations that instantly affect the operation and successful use of quarter-turn valves in waterworks systems.
The fourth edition of M49 is being developed to incorporate the changes in the quarter-turn valve product requirements and put in system interactions. A new chapter might be devoted to strategies of management valve sizing for fluid circulate, strain control and throttling in waterworks service. This methodology includes explanations on using strain, flow fee and cavitation graphical home windows to supply the person a radical image of valve performance over a range of anticipated system operating circumstances.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton started 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 labored at Val-Matic as Director of Engineering. He has participated in standards growing organizations, together with AWWA, MSS, ASSE and API. pressure gauge แบบ น้ำมัน holds BS and MS levels in Civil and Environmental Engineering together 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 efficiency prediction strategies for the nuclear energy industry.

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