Understanding Torque for Quarter-Turn Valves

Valve producers publish torques for his or her merchandise in order that actuation and mounting hardware can be correctly chosen. However, published torque values usually characterize solely the seating or unseating torque for a valve at its rated stress. While these are important values for reference, printed valve torques do not account for actual set up and working traits. In order to discover out the actual working torque for valves, it is necessary to understand the parameters of the piping techniques into which they’re put in. Factors similar to installation orientation, path of circulate and fluid velocity of the media all impact the precise working torque of valves.
Trunnion mounted ball valve operated by a single acting spring return actuator. Photo credit score: Val-Matic
The American Water Works Association (AWWA) publishes detailed data on calculating working torques for quarter-turn valves. This data 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 presently in its third version. In addition to data on butterfly valves, the present version additionally contains working torque calculations for different quarter-turn valves including plug valves and ball valves. Overall, this manual 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 standard for 3-in. through 72-in. butterfly valves, C504, was revealed in 1958 with 25, 50 and a hundred twenty five psi stress courses. In 1966 the 50 and 125 psi pressure lessons have been elevated to 75 and a hundred and fifty psi. The 250 psi stress class was added in 2000. The 78-in. and larger butterfly valve standard, C516, was first published in 2010 with 25, 50, seventy five and 150 psi pressure lessons with the 250 psi class added in 2014. The high-performance butterfly valve commonplace was published in 2018 and consists of 275 and 500 psi pressure classes as nicely as pushing the fluid circulate 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 commonplace, C507, for 6-in. through 48-in. ball valves in a hundred and fifty, 250 and 300 psi stress lessons was revealed in 1973. In 2011, measurement 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 standard for resilient-seated cast-iron eccentric plug valves in 1991, the primary a AWWA quarter-turn valve standard, C517, was not printed until 2005. The 2005 measurement vary was 3 in. via 72 in. with a a hundred seventy five
Example butterfly valve differential pressure (top) and move price management home windows (bottom)
stress 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) haven’t elevated the valve sizes or stress lessons. The addition of the A velocity designation (8 fps) was added within the 2017 edition. This valve is primarily used in wastewater service the place 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 under growth. This standard will encompass the same a hundred and fifty, 250 and 300 psi stress courses and the same fluid velocity designation of “D” (maximum 35 feet per second) as the current C507 ball valve standard.
In general, all of the valve sizes, flow charges and pressures have increased because the AWWA standard’s inception.
AWWA Manual M49 identifies 10 elements that affect working torque for quarter-turn valves. These parts fall into two general categories: (1) passive or friction-based parts, and (2) lively or dynamically generated parts. Because valve manufacturers can not know the actual piping system parameters when publishing torque values, printed torques are typically restricted to the 5 elements of passive or friction-based parts. These embrace:
Passive torque parts:
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 similar to valve orientation, media and move velocity. The components that make up lively torque embody:
Active torque elements:
Disc weight and center of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When contemplating all these varied active torque elements, it’s potential for the actual working torque to exceed the valve manufacturer’s published torque values.
Although quarter-turn valves have been used in the waterworks trade for a century, they are being uncovered to higher service stress and flow fee service circumstances. Since the quarter-turn valve’s closure member is all the time located in the flowing fluid, these higher service circumstances instantly impression the valve. Operation of these valves require an actuator to rotate and/or hold the closure member throughout the valve’s body as it reacts to all the fluid pressures and fluid move dynamic conditions.
In addition to the elevated service conditions, the valve sizes are additionally growing. The dynamic circumstances of the flowing fluid have greater impact on the bigger valve sizes. Therefore, the fluid dynamic effects become extra important than static differential stress and friction masses. Valves could be leak and hydrostatically shell examined throughout fabrication. However, the complete fluid circulate situations cannot be replicated before website set up.
Because of the trend for increased valve sizes and increased operating situations, it is more and more essential for the system designer, operator and proprietor of quarter-turn valves to higher understand the influence of system and fluid dynamics have on valve selection, building and use.
The AWWA Manual of Standard Practice M forty nine is dedicated to the understanding of quarter-turn valves including operating torque requirements, differential stress, flow situations, throttling, cavitation and system set up differences that instantly affect the operation and profitable use of quarter-turn valves in waterworks methods.
The fourth edition of M49 is being developed to include the changes within the quarter-turn valve product requirements and installed system interactions. A new chapter might be dedicated to methods of management valve sizing for fluid flow, stress management and throttling in waterworks service. This methodology contains explanations on using strain, flow price and cavitation graphical windows to offer the consumer an intensive picture of valve efficiency over a variety of anticipated system operating circumstances.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton began his profession as a consulting engineer in 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 previously worked at Val-Matic as Director of Engineering. เครื่องมือที่ใช้วัดความดันคือ has participated in requirements creating organizations, together with AWWA, MSS, ASSE and API. Dalton holds BS and MS degrees in Civil and Environmental Engineering together 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 lively 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 also worked with the Electric Power Research Institute (EPRI) in the growth of their quarter-turn valve efficiency prediction strategies for the nuclear power business.

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