Valve producers publish torques for his or her merchandise in order that actuation and mounting hardware can be properly selected. However, revealed torque values usually symbolize solely the seating or unseating torque for a valve at its rated strain. While these are important values for reference, published valve torques do not account for actual installation and working characteristics. In order to find out the precise working torque for valves, it’s necessary to understand the parameters of the piping methods into which they’re installed. Factors similar to set up orientation, path of flow and fluid velocity of the media all influence the actual operating 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 info on calculating operating torques for quarter-turn valves. This information appears in AWWA Manual M49 Quarter-Turn Valves: Head Loss, Torque, and Cavitation Analysis. Originally revealed in 2001 with torque calculations for butterfly valves, AWWA M49 is currently in its third edition. In addition to information on butterfly valves, the present version also contains operating 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 abstract 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 a hundred twenty five psi pressure courses. In 1966 the 50 and a hundred twenty five psi strain courses were increased to seventy five and 150 psi. The 250 psi strain class was added in 2000. The 78-in. and larger butterfly valve standard, C516, was first printed in 2010 with 25, 50, 75 and one hundred fifty psi strain lessons with the 250 psi class added in 2014. The high-performance butterfly valve normal was revealed in 2018 and includes 275 and 500 psi strain courses as properly as pushing the fluid move velocities above class B (16 toes per second) to class C (24 ft per second) and sophistication D (35 feet per second).
The first AWWA quarter-turn ball valve standard, C507, for 6-in. via 48-in. ball valves in a hundred and fifty, 250 and 300 psi strain courses was printed in 1973. In 2011, size vary was increased to 6-in. by way of 60-in. These valves have always 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 commonplace, C517, was not published till 2005. The 2005 size range was 3 in. by way of seventy two in. with a 175
Example butterfly valve differential strain (top) and move price management home windows (bottom)
pressure class for 3-in. by way of 12-in. sizes and 150 psi for the 14-in. through 72-in. The later editions (2009 and 2016) have not elevated the valve sizes or stress classes. The addition of the A velocity designation (8 fps) was added in the 2017 edition. 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 acknowledged in 2018 and the AWWA Rotary Cone Valves, 6 Inch Through 60 Inch (150 mm via 1,500 mm), C522, is beneath development. This standard will encompass the same 150, 250 and 300 psi strain lessons and the identical fluid velocity designation of “D” (maximum 35 feet per second) as the current C507 ball valve standard.
In common, all the valve sizes, flow rates and pressures have elevated since the AWWA standard’s inception.
AWWA Manual M49 identifies 10 parts that have an result on working torque for quarter-turn valves. These elements fall into two general classes: (1) passive or friction-based elements, and (2) lively or dynamically generated parts. Because valve manufacturers can not know the actual piping system parameters when publishing torque values, revealed torques are generally limited to the five 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 five parts are impacted by system parameters such as valve orientation, media and flow velocity. The parts 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 contemplating all these numerous lively torque elements, it is attainable for the precise working torque to exceed the valve manufacturer’s printed torque values.
Although quarter-turn valves have been used in the waterworks business for a century, they are being uncovered to larger service stress and circulate fee service circumstances. Since the quarter-turn valve’s closure member is at all times situated within the flowing fluid, these greater service conditions directly impression the valve. Operation of these valves require an actuator to rotate and/or maintain the closure member within the valve’s physique as it reacts to all of the fluid pressures and fluid flow dynamic circumstances.
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 larger valve sizes. Therefore, the fluid dynamic results turn out to be extra essential than static differential pressure and friction loads. Valves may be leak and hydrostatically shell examined during fabrication. However, the full fluid flow circumstances cannot be replicated before website set up.
Because of the trend for elevated valve sizes and increased working conditions, it’s increasingly necessary for the system designer, operator and proprietor of quarter-turn valves to raised understand 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 including working torque requirements, differential strain, move circumstances, throttling, cavitation and system set up differences that instantly affect the operation and profitable use of quarter-turn valves in waterworks systems.
The fourth edition of M49 is being developed to include the changes 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 flow, strain control and throttling in waterworks service. This methodology includes explanations on the use of stress, flow fee and cavitation graphical windows to provide the person a thorough image of valve performance over a spread of anticipated system working situations.
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About the Authors
Steve Dalton started his profession as a consulting engineer within the waterworks business 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 worked 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 concerned 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. เกจปรับแรงดันแก๊ส 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 labored with the Electric Power Research Institute (EPRI) in the growth of their quarter-turn valve performance prediction strategies for the nuclear energy trade.