Understanding Torque for Quarter-Turn Valves

Valve producers publish torques for their merchandise in order that actuation and mounting hardware can be correctly selected. However, revealed torque values usually represent solely the seating or unseating torque for a valve at its rated stress. While these are essential values for reference, published valve torques do not account for precise installation and operating traits. In order to determine the precise working torque for valves, it’s necessary to know the parameters of the piping techniques into which they’re installed. Factors corresponding to set up orientation, path of circulate and fluid velocity of the media all influence the precise 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 data on calculating working torques for quarter-turn valves. เกจวัดแรงดัน4บาร์ 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 at present in its third edition. In addition to information on butterfly valves, the present version also includes working torque calculations for other 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 operating torque.
Example torque calculation summary graph
The first AWWA quarter-turn valve commonplace for 3-in. by way of 72-in. butterfly valves, C504, was printed in 1958 with 25, 50 and one hundred twenty five psi pressure classes. In 1966 the 50 and one hundred twenty five psi pressure classes were increased to seventy five and a hundred and fifty psi. The 250 psi stress class was added in 2000. The 78-in. and larger butterfly valve standard, C516, was first published in 2010 with 25, 50, seventy five and a hundred and fifty psi pressure courses with the 250 psi class added in 2014. The high-performance butterfly valve commonplace was published in 2018 and contains 275 and 500 psi stress lessons in addition to pushing the fluid circulate velocities above class B (16 ft per second) to class C (24 toes per second) and sophistication D (35 toes per second).
The first AWWA quarter-turn ball valve standard, C507, for 6-in. via 48-in. ball valves in one hundred fifty, 250 and 300 psi strain classes was printed in 1973. In 2011, size range was elevated to 6-in. by way of 60-in. These valves have at all times 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 primary a AWWA quarter-turn valve normal, C517, was not printed till 2005. The 2005 size vary was 3 in. by way of seventy two in. with a one hundred seventy five
Example butterfly valve differential stress (top) and circulate fee control windows (bottom)
stress class for 3-in. via 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 stress lessons. The addition of the A velocity designation (8 fps) was added in the 2017 edition. This valve is primarily utilized in wastewater service where pressures and fluid velocities are maintained at decrease 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 through 1,500 mm), C522, is underneath development. This standard will embody the identical a hundred and fifty, 250 and 300 psi strain lessons and the identical fluid velocity designation of “D” (maximum 35 ft per second) as the present C507 ball valve commonplace.
In general, all of the valve sizes, flow charges and pressures have elevated for the reason that AWWA standard’s inception.
AWWA Manual M49 identifies 10 elements that have an result on working torque for quarter-turn valves. These parts fall into two common categories: (1) passive or friction-based parts, and (2) energetic or dynamically generated components. Because valve manufacturers can’t know the precise piping system parameters when publishing torque values, revealed torques are usually limited to the 5 parts of passive or friction-based parts. These include:
Passive torque parts:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The other 5 components are impacted by system parameters similar to valve orientation, media and move velocity. The elements that make up active torque embrace:
Active torque elements:
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 components, it is potential for the actual working torque to exceed the valve manufacturer’s revealed torque values.
Although quarter-turn valves have been used within the waterworks business for a century, they’re being exposed to larger service pressure and circulate fee service circumstances. Since the quarter-turn valve’s closure member is always positioned in the flowing fluid, these greater service situations immediately influence the valve. Operation of these valves require an actuator to rotate and/or maintain the closure member throughout the valve’s body as it reacts to all of the fluid pressures and fluid circulate dynamic situations.
In addition to the increased service conditions, the valve sizes are also growing. The dynamic situations of the flowing fluid have higher effect on the larger valve sizes. Therefore, the fluid dynamic results become extra essential than static differential strain and friction hundreds. Valves can be leak and hydrostatically shell examined during fabrication. However, the complete fluid move conditions cannot be replicated earlier than website set up.
Because of the development for increased valve sizes and elevated working conditions, it is more and more important for the system designer, operator and proprietor of quarter-turn valves to better understand the influence of system and fluid dynamics have on valve selection, building 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, flow situations, throttling, cavitation and system installation differences that immediately influence the operation and profitable use of quarter-turn valves in waterworks methods.
The fourth version of M49 is being developed to incorporate the adjustments in the quarter-turn valve product standards and put in system interactions. A new chapter might be devoted to methods of management valve sizing for fluid circulate, strain control and throttling in waterworks service. This methodology consists of explanations on the use of strain, flow price and cavitation graphical home windows to offer the consumer a radical image of valve performance over a spread of anticipated system working conditions.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton started his career 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 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 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 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 also worked with the Electric Power Research Institute (EPRI) within the growth of their quarter-turn valve performance prediction methods for the nuclear power industry.

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