Understanding Torque for Quarter-Turn Valves

Valve manufacturers publish torques for their products in order that actuation and mounting hardware may be properly selected. However, printed torque values often characterize solely the seating or unseating torque for a valve at its rated pressure. While these are necessary values for reference, published valve torques don’t account for precise installation and working characteristics. In order to find out the actual operating torque for valves, it is essential to know the parameters of the piping methods into which they’re installed. Factors corresponding to installation orientation, course of flow and fluid velocity of the media all impression the actual operating torque of valves.
Trunnion mounted ball valve operated by a single performing spring return actuator. Photo credit score: Val-Matic
The American Water Works Association (AWWA) publishes detailed information 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 printed in 2001 with torque calculations for butterfly valves, AWWA M49 is presently in its third edition. In addition to info on butterfly valves, the present edition additionally includes working torque calculations for other quarter-turn valves together with plug valves and ball valves. Overall, this guide identifies 10 parts of torque that can contribute to a quarter-turn valve’s operating torque.
Example torque calculation summary graph
The first AWWA quarter-turn valve commonplace for 3-in. through 72-in. butterfly valves, C504, was revealed in 1958 with 25, 50 and one hundred twenty five psi pressure classes. In 1966 the 50 and a hundred twenty five psi pressure courses were increased to 75 and 150 psi. The 250 psi stress class was added in 2000. The 78-in. and larger butterfly valve normal, C516, was first published in 2010 with 25, 50, seventy five and a hundred and fifty psi strain courses with the 250 psi class added in 2014. The high-performance butterfly valve normal was published in 2018 and includes 275 and 500 psi stress courses in addition to pushing the fluid circulate velocities above class B (16 toes per second) to class C (24 toes per second) and sophistication D (35 toes per second).
The first AWWA quarter-turn ball valve commonplace, C507, for 6-in. through 48-in. ball valves in 150, 250 and 300 psi stress lessons was published in 1973. In 2011, dimension range was increased to 6-in. through 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 standard for resilient-seated cast-iron eccentric plug valves in 1991, the primary a AWWA quarter-turn valve normal, C517, was not revealed till 2005. The 2005 measurement range was 3 in. via seventy two in. with a one hundred seventy five
Example butterfly valve differential strain (top) and move rate control home windows (bottom)
pressure class for 3-in. through 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 elevated the valve sizes or strain courses. The addition of the A velocity designation (8 fps) was added within the 2017 edition. This valve is primarily utilized in wastewater service the place pressures and fluid velocities are maintained at decrease 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 under growth. This commonplace will embody the identical a hundred and fifty, 250 and 300 psi stress classes and the identical fluid velocity designation of “D” (maximum 35 feet per second) as the present C507 ball valve normal.
In basic, all of the valve sizes, circulate charges and pressures have increased because the 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 common categories: (1) passive or friction-based parts, and (2) active or dynamically generated parts. Because valve manufacturers can’t know the actual piping system parameters when publishing torque values, printed torques are usually limited to the five parts 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 5 parts are impacted by system parameters similar to valve orientation, media and move velocity. The elements that make up lively torque embody:
Active torque components:
Disc weight and center of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When contemplating all these numerous energetic torque parts, it’s potential 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’re being exposed to higher service stress and circulate rate service situations. Since the quarter-turn valve’s closure member is always located within the flowing fluid, these larger service circumstances immediately influence the valve. Operation of those valves require an actuator to rotate and/or maintain the closure member within the valve’s body because it reacts to all of the fluid pressures and fluid circulate dynamic conditions.
In addition to the increased service conditions, the valve sizes are also increasing. The dynamic conditions of the flowing fluid have greater effect on the larger valve sizes. Therefore, the fluid dynamic results turn into more necessary than static differential strain and friction hundreds. Valves can be leak and hydrostatically shell examined during fabrication. However, the complete fluid circulate circumstances can’t be replicated before web site set up.
Because of the pattern for elevated valve sizes and elevated operating circumstances, it is increasingly essential for the system designer, operator and owner of quarter-turn valves to higher understand the impact of system and fluid dynamics have on valve selection, construction and use.
The AWWA Manual of Standard Practice M 49 is dedicated to the understanding of quarter-turn valves including operating torque requirements, differential stress, move situations, throttling, cavitation and system set up variations that directly influence the operation and successful use of quarter-turn valves in waterworks systems.
The fourth version of M49 is being developed to incorporate the modifications within the quarter-turn valve product requirements and installed system interactions. A new chapter shall be dedicated to methods of control valve sizing for fluid circulate, stress control and throttling in waterworks service. This methodology contains explanations on the use of pressure, circulate fee and cavitation graphical windows to offer the consumer an intensive image of valve performance over a range of anticipated system operating 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 beforehand labored 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 degrees in Civil and Environmental Engineering along 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 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.” pressure gauge weksler ราคา has additionally labored with the Electric Power Research Institute (EPRI) in the development of their quarter-turn valve performance prediction methods for the nuclear energy trade.

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