Valve manufacturers publish torques for their products so that actuation and mounting hardware could be properly selected. However, printed torque values typically characterize only the seating or unseating torque for a valve at its rated stress. While these are necessary values for reference, published valve torques do not account for precise installation and working traits. In order to discover out the actual operating torque for valves, it is necessary to understand the parameters of the piping systems into which they are put in. Factors such as set up orientation, direction of flow and fluid velocity of the media all impact the precise working torque of valves.
Trunnion mounted ball valve operated by a single performing spring return actuator. Photo credit: Val-Matic
The American Water Works Association (AWWA) publishes detailed information on calculating working torques for quarter-turn valves. This data appears 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 presently in its third edition. In addition to info on butterfly valves, the current version also includes working torque calculations for different quarter-turn valves together with plug valves and ball valves. Overall, this guide identifies 10 elements of torque that may contribute to a quarter-turn valve’s operating torque.
Example torque calculation summary graph
The first AWWA quarter-turn valve normal for 3-in. via 72-in. butterfly valves, C504, was revealed in 1958 with 25, 50 and a hundred twenty five psi pressure classes. In 1966 the 50 and one hundred twenty five psi stress courses had been elevated to seventy five and 150 psi. The 250 psi strain class was added in 2000. The 78-in. and larger butterfly valve normal, C516, was first printed 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 commonplace was published in 2018 and includes 275 and 500 psi strain classes in addition to pushing the fluid move velocities above class B (16 toes per second) to class C (24 feet per second) and class D (35 ft per second).
The first AWWA quarter-turn ball valve standard, C507, for 6-in. by way of 48-in. ball valves in one hundred fifty, 250 and 300 psi pressure lessons was revealed in 1973. In 2011, measurement range was elevated to 6-in. through 60-in. เกจวัดแรงดันอาร์กอน have all the time 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 normal for resilient-seated cast-iron eccentric plug valves in 1991, the first a AWWA quarter-turn valve commonplace, C517, was not printed till 2005. The 2005 measurement vary was 3 in. by way of seventy two in. with a a hundred seventy five
Example butterfly valve differential strain (top) and circulate fee control home windows (bottom)
strain class for 3-in. by way of 12-in. sizes and a hundred and fifty psi for the 14-in. through 72-in. The later editions (2009 and 2016) have not elevated the valve sizes or pressure classes. The addition of the A velocity designation (8 fps) was added within the 2017 edition. This valve is primarily utilized in wastewater service where pressures and fluid velocities are maintained at decrease values.
The want for a rotary cone valve was recognized in 2018 and the AWWA Rotary Cone Valves, 6 Inch Through 60 Inch (150 mm via 1,500 mm), C522, is underneath growth. This normal will encompass the same 150, 250 and 300 psi pressure courses and the identical fluid velocity designation of “D” (maximum 35 ft per second) as the current C507 ball valve commonplace.
In basic, all of the valve sizes, circulate rates and pressures have increased for the reason that AWWA standard’s inception.
AWWA Manual M49 identifies 10 parts that have an result on operating torque for quarter-turn valves. These parts fall into two general classes: (1) passive or friction-based components, and (2) energetic or dynamically generated elements. Because valve manufacturers cannot know the actual piping system parameters when publishing torque values, printed torques are generally limited to the 5 components of passive or friction-based components. These embrace:
Passive torque components:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The different 5 parts are impacted by system parameters similar to valve orientation, media and circulate velocity. The elements that make up active torque include:
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 actual working torque to exceed the valve manufacturer’s revealed 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 move price service circumstances. Since the quarter-turn valve’s closure member is at all times situated within the flowing fluid, these higher service situations directly influence the valve. Operation of those valves require an actuator to rotate and/or hold the closure member within the valve’s body because it reacts to all the fluid pressures and fluid flow dynamic situations.
In addition to the increased service circumstances, the valve sizes are also growing. The dynamic conditions of the flowing fluid have higher effect on the bigger valve sizes. Therefore, the fluid dynamic effects turn out to be extra important than static differential stress and friction hundreds. Valves could be leak and hydrostatically shell tested throughout fabrication. However, the total fluid circulate situations cannot be replicated earlier than web site installation.
Because of the development for elevated valve sizes and elevated operating situations, it’s more and more necessary for the system designer, operator and proprietor of quarter-turn valves to higher understand the impression of system and fluid dynamics have on valve selection, construction and use.
The AWWA Manual of Standard Practice M 49 is devoted to the understanding of quarter-turn valves including working torque necessities, differential pressure, move situations, throttling, cavitation and system installation variations that directly affect the operation and successful use of quarter-turn valves in waterworks techniques.
The fourth version of M49 is being developed to incorporate the modifications within the quarter-turn valve product standards and put in system interactions. A new chapter will be dedicated to methods of management valve sizing for fluid flow, stress control and throttling in waterworks service. This methodology includes explanations on using strain, flow price and cavitation graphical windows to provide the user a radical picture of valve efficiency over a variety of anticipated system working circumstances.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton began his profession 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 beforehand labored at Val-Matic as Director of Engineering. He has participated in standards creating organizations, together with AWWA, MSS, ASSE and API. Dalton holds BS and MS levels in Civil and Environmental Engineering together 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 lively 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 additionally labored with the Electric Power Research Institute (EPRI) in the growth of their quarter-turn valve performance prediction strategies for the nuclear energy business.