Understanding Torque for Quarter-Turn Valves

Valve producers publish torques for their merchandise so that actuation and mounting hardware may be properly chosen. However, revealed torque values typically characterize only the seating or unseating torque for a valve at its rated pressure. While these are important values for reference, revealed valve torques don’t account for precise installation and operating traits. In order to discover out the precise operating torque for valves, it’s essential to understand the parameters of the piping methods into which they’re installed. Factors such as set up orientation, path of circulate and fluid velocity of the media all impact the actual operating torque of valves.
เกจ์แรงดัน mounted ball valve operated by a single appearing spring return actuator. Photo credit score: Val-Matic
The American Water Works Association (AWWA) publishes detailed data 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 currently in its third edition. In addition to info on butterfly valves, the present version additionally includes operating torque calculations for different quarter-turn valves including plug valves and ball valves. Overall, this guide identifies 10 parts of torque that may contribute to a quarter-turn valve’s working torque.
Example torque calculation summary 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 one hundred twenty five psi pressure lessons. In 1966 the 50 and a hundred twenty five psi pressure classes were increased to 75 and one hundred fifty psi. The 250 psi stress class was added in 2000. The 78-in. and bigger butterfly valve normal, C516, was first printed in 2010 with 25, 50, seventy five and one hundred fifty psi stress classes with the 250 psi class added in 2014. The high-performance butterfly valve standard was revealed in 2018 and contains 275 and 500 psi stress lessons as properly as pushing the fluid circulate velocities above class B (16 ft per second) to class C (24 ft per second) and class D (35 feet per second).
The first AWWA quarter-turn ball valve normal, C507, for 6-in. via 48-in. ball valves in 150, 250 and 300 psi strain classes was revealed in 1973. In 2011, dimension vary was elevated to 6-in. via 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 normal, C517, was not published until 2005. The 2005 size vary was 3 in. via 72 in. with a one hundred seventy five
Example butterfly valve differential stress (top) and flow price management home windows (bottom)
strain class for 3-in. by way of 12-in. sizes and 150 psi for the 14-in. via 72-in. The later editions (2009 and 2016) have not elevated the valve sizes or strain classes. The addition of the A velocity designation (8 fps) was added in the 2017 version. This valve is primarily used in wastewater service where pressures and fluid velocities are maintained at decrease 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 standard will embody the same a hundred and fifty, 250 and 300 psi stress lessons and the same fluid velocity designation of “D” (maximum 35 feet per second) as the present C507 ball valve standard.
In common, all of the valve sizes, flow charges and pressures have elevated for the reason that AWWA standard’s inception.
AWWA Manual M49 identifies 10 components that affect operating torque for quarter-turn valves. These elements fall into two general categories: (1) passive or friction-based parts, and (2) energetic or dynamically generated parts. Because valve producers cannot know the actual piping system parameters when publishing torque values, revealed torques are usually limited to the 5 components of passive or friction-based elements. These embrace:
Passive torque components:
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 such as valve orientation, media and move velocity. The components that make up active torque embrace:
Active torque elements:
Disc weight and middle of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When considering all these numerous lively torque elements, it is 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 uncovered to larger service pressure and flow fee service conditions. Since the quarter-turn valve’s closure member is always situated in 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 circumstances.
In addition to the increased service situations, the valve sizes are additionally growing. 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 essential than static differential strain and friction loads. Valves may be leak and hydrostatically shell examined during fabrication. However, the complete fluid circulate conditions cannot be replicated before web site installation.
Because of the development for increased valve sizes and increased operating conditions, it is more and more necessary for the system designer, operator and owner of quarter-turn valves to better perceive the influence of system and fluid dynamics have on valve choice, 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 stress, flow circumstances, throttling, cavitation and system installation variations that immediately influence the operation and successful use of quarter-turn valves in waterworks systems.
The fourth version of M49 is being developed to include the modifications within the quarter-turn valve product requirements and installed system interactions. A new chapter might be dedicated to strategies of control valve sizing for fluid move, stress control and throttling in waterworks service. This methodology contains explanations on using stress, flow fee and cavitation graphical windows to supply the user a radical image of valve performance over a variety of anticipated system working conditions.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton began his career as a consulting engineer in 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 worked 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 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 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 also worked with the Electric Power Research Institute (EPRI) in the growth of their quarter-turn valve performance prediction methods for the nuclear energy business.