Understanding Torque for Quarter-Turn Valves

Valve producers publish torques for their merchandise in order that actuation and mounting hardware could be properly chosen. However, printed torque values often represent solely the seating or unseating torque for a valve at its rated pressure. While Bizarre are essential values for reference, revealed valve torques don’t account for precise installation and working characteristics. In order to determine the precise working torque for valves, it’s essential to grasp the parameters of the piping techniques into which they’re put in. Factors similar to set up orientation, course of move and fluid velocity of the media all impact the actual 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 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 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 also includes working torque calculations for different quarter-turn valves including plug valves and ball valves. Overall, this manual identifies 10 elements 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. via 72-in. butterfly valves, C504, was published in 1958 with 25, 50 and one hundred twenty five psi strain classes. In 1966 the 50 and one hundred twenty five psi pressure lessons were increased to seventy five and a hundred and fifty psi. The 250 psi stress class was added in 2000. The 78-in. and bigger butterfly valve standard, C516, was first printed in 2010 with 25, 50, seventy five and 150 psi stress courses with the 250 psi class added in 2014. The high-performance butterfly valve commonplace was revealed in 2018 and includes 275 and 500 psi strain courses as nicely as pushing the fluid move velocities above class B (16 toes per second) to class C (24 ft per second) and class D (35 toes per second).
The first AWWA quarter-turn ball valve standard, C507, for 6-in. via 48-in. ball valves in a hundred and fifty, 250 and 300 psi pressure courses was printed in 1973. In 2011, measurement range was elevated to 6-in. through 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 primary a AWWA quarter-turn valve standard, C517, was not printed till 2005. The 2005 measurement range was three in. via 72 in. with a 175
Example butterfly valve differential pressure (top) and circulate price control home windows (bottom)
pressure class for 3-in. via 12-in. sizes and one hundred fifty psi for the 14-in. by way of 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 within the 2017 edition. This valve is primarily utilized 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 by way of 1,500 mm), C522, is under growth. This standard will embody the identical one hundred 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, move rates and pressures have increased since the AWWA standard’s inception.
AWWA Manual M49 identifies 10 components that have an effect on operating torque for quarter-turn valves. These parts fall into two general classes: (1) passive or friction-based components, and (2) active or dynamically generated elements. Because valve manufacturers can not know the actual piping system parameters when publishing torque values, revealed 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 different five components are impacted by system parameters similar to valve orientation, media and move velocity. The parts that make up active torque include:
Active torque parts:
Disc weight and heart of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When considering all these numerous energetic 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 business for a century, they’re being exposed to larger service stress and circulate price service conditions. Since the quarter-turn valve’s closure member is all the time located in the flowing fluid, these greater service conditions directly impact 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 move dynamic situations.
In addition to the increased service situations, the valve sizes are also rising. The dynamic conditions of the flowing fluid have larger impact on the bigger valve sizes. Therefore, the fluid dynamic effects turn out to be more important than static differential stress and friction hundreds. Valves could be leak and hydrostatically shell tested during fabrication. However, the total fluid move conditions can’t be replicated earlier than web site installation.
Because of the trend for increased valve sizes and elevated operating circumstances, it is increasingly essential 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 49 is devoted to the understanding of quarter-turn valves together with operating torque requirements, differential pressure, move circumstances, throttling, cavitation and system installation differences that directly 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 within 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 control and throttling in waterworks service. This methodology consists of explanations on using strain, move rate and cavitation graphical windows to offer the person a radical picture of valve performance over a range of anticipated system operating situations.
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 growing organizations, together with AWWA, MSS, ASSE and API. Dalton holds BS and MS levels 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 energetic 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 also labored with the Electric Power Research Institute (EPRI) in the growth of their quarter-turn valve performance prediction strategies for the nuclear energy industry.

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