Understanding Torque for Quarter-Turn Valves

Valve manufacturers publish torques for their products so that actuation and mounting hardware can be properly chosen. However, published torque values usually represent only the seating or unseating torque for a valve at its rated stress. While these are important values for reference, revealed valve torques don’t account for actual set up and operating traits. In order to discover out the precise operating torque for valves, it is necessary to know the parameters of the piping methods into which they’re put in. Factors corresponding to set up orientation, course of flow and fluid velocity of the media all influence the actual operating torque of valves.
Trunnion mounted ball valve operated by a single acting spring return actuator. Photo credit: Val-Matic
The American Water Works Association (AWWA) publishes detailed data on calculating operating torques for quarter-turn valves. This data appears 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 at present in its third version. In addition to info 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 components of torque that may contribute to a quarter-turn valve’s operating torque.
Example torque calculation summary graph
The first AWWA quarter-turn valve normal for 3-in. by way of 72-in. butterfly valves, C504, was published in 1958 with 25, 50 and one hundred twenty five psi stress lessons. In 1966 the 50 and one hundred twenty five psi strain classes have been elevated to 75 and one hundred fifty psi. The 250 psi stress 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 a hundred and fifty psi pressure classes with the 250 psi class added in 2014. The high-performance butterfly valve commonplace was published in 2018 and includes 275 and 500 psi pressure classes as well as pushing the fluid move velocities above class B (16 toes per second) to class C (24 toes per second) and sophistication D (35 feet per second).
The first AWWA quarter-turn ball valve commonplace, C507, for 6-in. through 48-in. ball valves in 150, 250 and 300 psi pressure courses was published in 1973. In 2011, size vary 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 commonplace for resilient-seated cast-iron eccentric plug valves in 1991, the first a AWWA quarter-turn valve standard, C517, was not revealed till 2005. The 2005 dimension vary was 3 in. via 72 in. with a a hundred seventy five
Example butterfly valve differential stress (top) and circulate fee control home windows (bottom)
pressure class for 3-in. via 12-in. sizes and one hundred fifty psi for the 14-in. through 72-in. The later editions (2009 and 2016) haven’t increased the valve sizes or strain lessons. 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 want for a rotary cone valve was acknowledged in 2018 and the AWWA Rotary Cone Valves, 6 Inch Through 60 Inch (150 mm through 1,500 mm), C522, is beneath improvement. This standard will embody the same 150, 250 and 300 psi pressure lessons and the same fluid velocity designation of “D” (maximum 35 ft per second) as the current C507 ball valve standard.
In basic, all the valve sizes, circulate charges and pressures have elevated because the AWWA standard’s inception.
AWWA Manual M49 identifies 10 components that have an result on operating torque for quarter-turn valves. These parts fall into two common categories: (1) passive or friction-based components, and (2) energetic or dynamically generated elements. Because valve manufacturers can’t know the precise piping system parameters when publishing torque values, printed torques are usually limited to the five parts of passive or friction-based components. These embrace:
Passive torque components:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The different 5 elements are impacted by system parameters similar to valve orientation, media and move velocity. The elements that make up energetic torque include:
Active torque components:
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 potential for the precise operating torque to exceed the valve manufacturer’s printed torque values.
Although quarter-turn valves have been used within the waterworks business for a century, they are being uncovered to larger service pressure and circulate rate service situations. Since the quarter-turn valve’s closure member is always situated in the flowing fluid, these greater service circumstances immediately impact the valve. Operation of those valves require an actuator to rotate and/or hold the closure member throughout the valve’s body because it reacts to all the fluid pressures and fluid circulate dynamic situations.
In addition to the increased service conditions, the valve sizes are additionally rising. The dynamic circumstances of the flowing fluid have greater effect on the larger valve sizes. Therefore, the fluid dynamic effects become more necessary than static differential stress and friction loads. Valves can be leak and hydrostatically shell tested throughout fabrication. However, the full fluid circulate situations can’t be replicated before website set up.
Because of the trend for elevated valve sizes and elevated operating circumstances, it is more and more essential for the system designer, operator and proprietor of quarter-turn valves to better understand the impact of system and fluid dynamics have on valve selection, construction and use.
The AWWA Manual of Standard Practice M 49 is devoted to the understanding of quarter-turn valves including operating torque necessities, differential strain, circulate conditions, throttling, cavitation and system set up variations that instantly influence the operation and profitable use of quarter-turn valves in waterworks systems.
The fourth version of M49 is being developed to incorporate the changes in the quarter-turn valve product standards and put in system interactions. A new chapter might be dedicated to methods of management valve sizing for fluid move, pressure management and throttling in waterworks service. This methodology consists of explanations on using strain, circulate price and cavitation graphical windows to supply the consumer a thorough picture of valve efficiency over a spread of anticipated system working circumstances.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton started his career as a consulting engineer within 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 developing organizations, including AWWA, MSS, ASSE and API. Dalton holds BS and MS degrees in Civil and Environmental Engineering together with Professional Engineering Registration.
เครื่องมือวัดความดัน has been concerned 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 more 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) in the improvement of their quarter-turn valve efficiency prediction methods for the nuclear energy business.

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