Understanding Torque for Quarter-Turn Valves

Valve manufacturers publish torques for his or her products in order that actuation and mounting hardware can be correctly chosen. However, published torque values typically symbolize solely the seating or unseating torque for a valve at its rated pressure. While these are important values for reference, printed valve torques do not account for precise installation and operating characteristics. In order to discover out the precise working torque for valves, it’s needed to grasp the parameters of the piping methods into which they’re put in. Factors such as set up orientation, direction of circulate and fluid velocity of the media all impression the actual operating 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 info on calculating operating 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 at present in its third edition. In addition to info on butterfly valves, the current edition additionally consists of working torque calculations for other quarter-turn valves including plug valves and ball valves. Overall, this guide 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 standard for 3-in. through 72-in. butterfly valves, C504, was printed in 1958 with 25, 50 and one hundred twenty five psi stress classes. In 1966 the 50 and 125 psi strain courses were elevated to seventy five and a hundred and fifty psi. The 250 psi strain class was added in 2000. The 78-in. and larger butterfly valve normal, C516, was first published in 2010 with 25, 50, 75 and one hundred fifty psi pressure lessons with the 250 psi class added in 2014. The high-performance butterfly valve normal was printed in 2018 and consists of 275 and 500 psi pressure lessons as properly as pushing the fluid flow velocities above class B (16 feet 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. through 48-in. ball valves in 150, 250 and 300 psi stress classes was printed in 1973. In 2011, dimension range was increased to 6-in. by way of 60-in. These valves have at all times 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 standard, C517, was not printed till 2005. The 2005 size vary was 3 in. through seventy two in. with a 175
Example butterfly valve differential stress (top) and flow rate control windows (bottom)
stress class for 3-in. through 12-in. sizes and one hundred fifty psi for the 14-in. through 72-in. The later editions (2009 and 2016) have not increased the valve sizes or pressure 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 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 via 1,500 mm), C522, is under development. This commonplace will embody the identical one hundred fifty, 250 and 300 psi pressure courses and the same fluid velocity designation of “D” (maximum 35 ft per second) as the current C507 ball valve commonplace.
In general, all of the valve sizes, circulate rates and pressures have increased for the explanation that AWWA standard’s inception.
AWWA Manual M49 identifies 10 parts that have an effect on operating torque for quarter-turn valves. These components fall into two basic classes: (1) passive or friction-based components, and (2) active or dynamically generated parts. Because valve manufacturers cannot know the precise piping system parameters when publishing torque values, published torques are generally restricted to the 5 parts of passive or friction-based components. These embrace:
Passive torque elements:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The other five components are impacted by system parameters corresponding to valve orientation, media and circulate velocity. The parts that make up lively torque embrace:
Active torque components:
Disc weight and middle of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When considering all these varied energetic torque elements, it is potential for the precise working torque to exceed the valve manufacturer’s published torque values.
Although quarter-turn valves have been used in the waterworks industry for a century, they’re being exposed to higher service pressure and move price service conditions. Since the quarter-turn valve’s closure member is at all times situated within the flowing fluid, these greater service circumstances immediately impact the valve. Operation of these valves require an actuator to rotate and/or maintain the closure member throughout the valve’s physique because it reacts to all the fluid pressures and fluid flow dynamic situations.
In addition to the elevated service conditions, the valve sizes are additionally growing. The dynamic situations of the flowing fluid have higher impact on the larger valve sizes. Therefore, the fluid dynamic effects become extra important than static differential pressure and friction masses. Valves can be leak and hydrostatically shell tested during fabrication. However, the complete fluid flow situations can’t be replicated earlier than web site installation.
Because of the pattern for increased valve sizes and elevated operating conditions, it’s increasingly necessary for the system designer, operator and owner of quarter-turn valves to higher understand the influence of system and fluid dynamics have on valve choice, development and use.
The AWWA Manual of Standard Practice M 49 is dedicated to the understanding of quarter-turn valves together with working torque necessities, differential pressure, circulate conditions, throttling, cavitation and system set up variations that directly influence the operation and profitable use of quarter-turn valves in waterworks systems.
The fourth edition of M49 is being developed to incorporate the adjustments within the quarter-turn valve product standards and put in system interactions. A new chapter shall be dedicated to methods of management valve sizing for fluid flow, strain management and throttling in waterworks service. This methodology contains explanations on using stress, move fee and cavitation graphical windows to supply the consumer an intensive picture of valve performance over a range 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 industry in Chicago. ส่วนประกอบpressuregauge joined Val-Matic in 2011 and was appointed president of Val-Matic in May 2021, following the retirement of John Ballun. Dalton beforehand labored at Val-Matic as Director of Engineering. He has participated in requirements growing organizations, including AWWA, MSS, ASSE and API. Dalton holds BS and MS levels 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 energetic 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 additionally worked with the Electric Power Research Institute (EPRI) in the development of their quarter-turn valve performance prediction strategies for the nuclear power business.

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