Understanding Torque for Quarter-Turn Valves

Valve producers publish torques for their products in order that actuation and mounting hardware can be properly chosen. However, revealed torque values usually represent solely the seating or unseating torque for a valve at its rated pressure. While these are necessary values for reference, revealed valve torques don’t account for actual set up and working traits. In order to determine the actual working torque for valves, it’s necessary to grasp the parameters of the piping techniques into which they’re installed. Factors similar to set up orientation, path of circulate and fluid velocity of the media all impact the actual operating torque of valves.
Trunnion mounted ball valve operated by a single acting spring return actuator. เกจวัดแรงดันออกซิเจนราคา : Val-Matic
The American Water Works Association (AWWA) publishes detailed data on calculating working torques for quarter-turn valves. This data 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 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 handbook 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 normal for 3-in. by way of 72-in. butterfly valves, C504, was revealed in 1958 with 25, 50 and 125 psi stress courses. In 1966 the 50 and one hundred twenty five psi stress lessons were increased to seventy five and one hundred fifty psi. The 250 psi stress class was added in 2000. The 78-in. and larger butterfly valve commonplace, C516, was first printed in 2010 with 25, 50, 75 and a hundred and fifty psi stress classes with the 250 psi class added in 2014. The high-performance butterfly valve standard was published in 2018 and contains 275 and 500 psi stress classes as properly as pushing the fluid move velocities above class B (16 ft per second) to class C (24 toes per second) and sophistication D (35 feet per second).
The first AWWA quarter-turn ball valve normal, C507, for 6-in. via 48-in. ball valves in 150, 250 and 300 psi stress lessons was printed in 1973. In 2011, dimension vary was increased to 6-in. through 60-in. These valves have all the time 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 normal for resilient-seated cast-iron eccentric plug valves in 1991, the first a AWWA quarter-turn valve normal, C517, was not published till 2005. The 2005 dimension vary was 3 in. by way of 72 in. with a 175
Example butterfly valve differential strain (top) and move fee control windows (bottom)
pressure class for 3-in. by way of 12-in. sizes and a hundred and fifty psi for the 14-in. via 72-in. The later editions (2009 and 2016) haven’t increased the valve sizes or stress lessons. The addition of the A velocity designation (8 fps) was added in 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 through 1,500 mm), C522, is underneath growth. This standard will embody the same one hundred fifty, 250 and 300 psi strain lessons and the identical fluid velocity designation of “D” (maximum 35 ft per second) as the current C507 ball valve normal.
In common, 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 effect on working torque for quarter-turn valves. These components fall into two basic classes: (1) passive or friction-based components, and (2) active or dynamically generated components. Because valve producers can’t know the precise piping system parameters when publishing torque values, revealed torques are generally limited to the five elements of passive or friction-based elements. These embrace:
Passive torque components:
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 such as valve orientation, media and flow velocity. The elements that make up active torque embody:
Active torque parts:
Disc weight and center of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When contemplating all these varied lively torque components, it’s attainable for the actual operating torque to exceed the valve manufacturer’s revealed torque values.
Although quarter-turn valves have been used within the waterworks business for a century, they are being exposed to greater service strain and move fee service conditions. Since the quarter-turn valve’s closure member is at all times situated in the flowing fluid, these greater service situations immediately influence the valve. Operation of these valves require an actuator to rotate and/or maintain the closure member inside the valve’s body as it reacts to all of the fluid pressures and fluid move dynamic situations.
In addition to the elevated service conditions, the valve sizes are also increasing. The dynamic situations of the flowing fluid have greater effect on the larger valve sizes. Therefore, the fluid dynamic effects turn out to be more essential than static differential stress and friction loads. Valves can be leak and hydrostatically shell tested throughout fabrication. However, the full fluid flow situations can’t be replicated earlier than website set up.
Because of the pattern for elevated valve sizes and elevated working circumstances, it’s more and more important for the system designer, operator and owner of quarter-turn valves to higher perceive 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 requirements, differential stress, circulate circumstances, throttling, cavitation and system installation variations that instantly affect the operation and profitable use of quarter-turn valves in waterworks systems.
The fourth edition of M49 is being developed to include the adjustments in the quarter-turn valve product requirements and put in system interactions. A new chapter might be devoted to methods of management valve sizing for fluid move, stress control and throttling in waterworks service. This methodology contains explanations on using pressure, flow rate and cavitation graphical home windows to offer the user a radical image of valve performance over a variety of anticipated system working conditions.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton started his career as a consulting engineer in 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, 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 involved 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 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 additionally worked with the Electric Power Research Institute (EPRI) in the improvement of their quarter-turn valve performance prediction methods for the nuclear power trade.

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