Understanding Torque for Quarter-Turn Valves

Valve producers publish torques for their merchandise in order that actuation and mounting hardware may be correctly selected. However, revealed torque values often symbolize only the seating or unseating torque for a valve at its rated strain. While these are important values for reference, published valve torques don’t account for actual set up and working characteristics. In order to find out the precise operating torque for valves, it’s essential to grasp the parameters of the piping methods into which they’re put in. Factors such as set up orientation, path of flow and fluid velocity of the media all influence 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 operating torques for quarter-turn valves. This information 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 currently in its third version. In addition to information on butterfly valves, the current edition additionally 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 abstract graph
The first AWWA quarter-turn valve normal for 3-in. through 72-in. butterfly valves, C504, was published in 1958 with 25, 50 and a hundred twenty five psi stress courses. In 1966 the 50 and one hundred twenty five psi strain courses 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 normal, C516, was first printed in 2010 with 25, 50, 75 and a hundred and fifty psi pressure classes 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 courses in addition to pushing the fluid circulate velocities above class B (16 toes per second) to class C (24 feet 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 one hundred fifty, 250 and 300 psi strain courses was printed in 1973. In 2011, size range was elevated to 6-in. via 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 commonplace for resilient-seated cast-iron eccentric plug valves in 1991, the first a AWWA quarter-turn valve normal, C517, was not printed until 2005. The 2005 size vary was 3 in. via 72 in. with a one hundred seventy five
Example butterfly valve differential strain (top) and circulate rate 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) have not increased the valve sizes or stress courses. The addition of the A velocity designation (8 fps) was added in the 2017 version. 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 recognized in 2018 and the AWWA Rotary Cone Valves, 6 Inch Through 60 Inch (150 mm by way of 1,500 mm), C522, is beneath development. This commonplace will embody the same 150, 250 and 300 psi stress lessons and the identical fluid velocity designation of “D” (maximum 35 toes per second) as the present C507 ball valve normal.
In common, all the valve sizes, flow charges and pressures have elevated for the rationale that AWWA standard’s inception.
AWWA Manual M49 identifies 10 elements that affect working torque for quarter-turn valves. These elements fall into two common classes: (1) passive or friction-based parts, and (2) lively or dynamically generated parts. Because valve producers can’t know the precise piping system parameters when publishing torque values, published torques are usually restricted to the five elements of passive or friction-based components. These include:
Passive torque elements:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The other five elements are impacted by system parameters corresponding to valve orientation, media and flow velocity. The components that make up lively 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 various lively torque elements, it’s attainable for the actual operating 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 are being exposed to larger service strain and circulate rate service situations. Since the quarter-turn valve’s closure member is at all times located within the flowing fluid, these larger service situations immediately impact the valve. Operation of those valves require an actuator to rotate and/or maintain the closure member within the valve’s physique as it reacts to all the fluid pressures and fluid circulate dynamic conditions.
In addition to the elevated service conditions, the valve sizes are additionally increasing. The dynamic circumstances of the flowing fluid have higher effect on the bigger valve sizes. Therefore, the fluid dynamic effects turn out to be more necessary than static differential stress and friction loads. เกจวัดแรงกด could be leak and hydrostatically shell tested throughout fabrication. However, the total fluid flow circumstances cannot be replicated earlier than website installation.
Because of the pattern for elevated valve sizes and elevated operating conditions, it’s more and more necessary for the system designer, operator and owner of quarter-turn valves to higher understand the impression of system and fluid dynamics have on valve choice, construction and use.
The AWWA Manual of Standard Practice M 49 is devoted to the understanding of quarter-turn valves together with operating torque necessities, differential strain, move situations, throttling, cavitation and system installation differences that instantly affect the operation and successful use of quarter-turn valves in waterworks systems.
The fourth edition of M49 is being developed to incorporate the modifications in the quarter-turn valve product requirements and installed system interactions. A new chapter shall be dedicated to methods of control valve sizing for fluid move, strain control and throttling in waterworks service. This methodology contains explanations on the utilization of stress, circulate fee and cavitation graphical home windows to supply the consumer a thorough image of valve efficiency over a range of anticipated system working conditions.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton began his career as a consulting engineer within 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 requirements creating 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 improvement of their quarter-turn valve efficiency prediction strategies for the nuclear energy business.

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