Understanding Torque for Quarter-Turn Valves

Valve producers publish torques for their products in order that actuation and mounting hardware may be properly selected. However, published torque values typically represent only the seating or unseating torque for a valve at its rated stress. While these are essential values for reference, printed valve torques do not account for actual installation and working traits. In order to determine the actual operating torque for valves, it’s necessary to grasp the parameters of the piping systems into which they are installed. Factors such as set up orientation, path of circulate and fluid velocity of the media all impression the actual working 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 working torques for quarter-turn valves. This info 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 edition. In addition to data on butterfly valves, the present edition also consists of working torque calculations for different quarter-turn valves including plug valves and ball valves. Overall, this manual identifies 10 components of torque that may 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 lessons. In 1966 the 50 and a hundred twenty five psi pressure lessons had been increased to seventy five and 150 psi. The 250 psi strain class was added in 2000. The 78-in. and larger butterfly valve normal, C516, was first revealed in 2010 with 25, 50, 75 and a hundred and fifty psi pressure courses with the 250 psi class added in 2014. The high-performance butterfly valve standard was published in 2018 and includes 275 and 500 psi strain lessons as properly as pushing the fluid flow velocities above class B (16 feet per second) to class C (24 toes per second) and class D (35 toes per second).
The first AWWA quarter-turn ball valve normal, C507, for 6-in. by way of 48-in. ball valves in one hundred fifty, 250 and 300 psi strain classes was published in 1973. In 2011, dimension vary 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 standard for resilient-seated cast-iron eccentric plug valves in 1991, the first a AWWA quarter-turn valve commonplace, C517, was not revealed until 2005. The 2005 size vary was three in. via seventy two in. with a a hundred seventy five
Example butterfly valve differential strain (top) and flow price control home windows (bottom)
stress class for 3-in. through 12-in. sizes and 150 psi for the 14-in. by way of 72-in. The later editions (2009 and 2016) have not increased the valve sizes or strain courses. The addition of the A velocity designation (8 fps) was added within the 2017 version. This valve is primarily used in wastewater service where pressures and fluid velocities are maintained at lower values.
The want for a rotary cone valve was recognized in 2018 and the AWWA Rotary Cone Valves, 6 Inch Through 60 Inch (150 mm via 1,500 mm), C522, is underneath growth. This commonplace will encompass the identical a hundred and fifty, 250 and 300 psi strain courses and the identical fluid velocity designation of “D” (maximum 35 toes per second) as the current C507 ball valve normal.
In basic, all the valve sizes, flow rates and pressures have elevated because the AWWA standard’s inception.
AWWA Manual M49 identifies 10 elements that affect working torque for quarter-turn valves. These components fall into two basic categories: (1) passive or friction-based elements, and (2) active or dynamically generated components. Because valve producers can not know the actual piping system parameters when publishing torque values, printed torques are usually limited to the 5 elements of passive or friction-based components. These include:
Passive torque parts:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The different five elements are impacted by system parameters corresponding to valve orientation, media and flow velocity. The parts that make up energetic torque embody:
Active torque components:
Disc weight and heart of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When contemplating all these numerous energetic torque components, it’s possible for the precise working torque to exceed the valve manufacturer’s revealed torque values.
Although quarter-turn valves have been used within the waterworks industry for a century, they’re being exposed to larger service stress and move rate service conditions. Since the quarter-turn valve’s closure member is always located within the flowing fluid, these greater service conditions directly impact the valve. Operation of those valves require an actuator to rotate and/or hold the closure member throughout the valve’s body as it reacts to all of the fluid pressures and fluid circulate dynamic conditions.
In addition to the elevated service circumstances, the valve sizes are additionally increasing. The dynamic situations of the flowing fluid have greater impact on the larger valve sizes. Therefore, the fluid dynamic effects turn out to be extra important than static differential pressure and friction loads. Valves may be leak and hydrostatically shell tested during fabrication. However, the total fluid circulate conditions can’t be replicated earlier than site installation.
Because of the pattern for elevated valve sizes and elevated operating circumstances, it’s more and more necessary for the system designer, operator and proprietor of quarter-turn valves to higher perceive 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 working torque requirements, differential stress, move circumstances, throttling, cavitation and system installation differences that directly affect the operation and profitable use of quarter-turn valves in waterworks techniques.
AWWA MANUAL OF STANDARD PRACTICE M49 4TH EDITION เกวัดแรงดัน of M49 is being developed to include the adjustments within the quarter-turn valve product requirements and installed system interactions. A new chapter will be devoted to strategies of control valve sizing for fluid circulate, pressure management and throttling in waterworks service. This methodology consists of explanations on the use of stress, circulate price and cavitation graphical home windows to provide the person a thorough image of valve efficiency over a range of anticipated system operating situations.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton started his profession as a consulting engineer within 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 labored at Val-Matic as Director of Engineering. He has participated in standards growing organizations, including AWWA, MSS, ASSE and API. Dalton holds BS and MS degrees in Civil and Environmental Engineering along 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) within the development of their quarter-turn valve performance prediction methods for the nuclear energy trade.

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