Valve manufacturers publish torques for their merchandise in order that actuation and mounting hardware could be properly selected. However, revealed torque values often represent solely the seating or unseating torque for a valve at its rated strain. While these are important values for reference, revealed valve torques don’t account for precise installation and operating traits. In order to determine the actual operating torque for valves, it’s essential to grasp the parameters of the piping systems into which they are put in. Factors such as set up orientation, direction of circulate and fluid velocity of the media all influence the precise working torque of valves.
Trunnion mounted ball valve operated by a single appearing spring return actuator. เกจวัดแรงดันpcp : Val-Matic
The American Water Works Association (AWWA) publishes detailed information on calculating operating torques for quarter-turn valves. This info 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 version. In addition to information on butterfly valves, the present version additionally contains operating torque calculations for different quarter-turn valves including plug valves and ball valves. Overall, this handbook identifies 10 components of torque that may contribute to a quarter-turn valve’s operating torque.
Example torque calculation abstract graph
AWWA QUARTER-TURN VALVE HISTORY
The first AWWA quarter-turn valve normal for 3-in. via 72-in. butterfly valves, C504, was revealed in 1958 with 25, 50 and one hundred twenty five psi strain classes. In 1966 the 50 and a hundred twenty five psi pressure lessons were elevated to seventy five and 150 psi. The 250 psi stress class was added in 2000. The 78-in. and bigger butterfly valve commonplace, C516, was first revealed 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 commonplace was printed in 2018 and includes 275 and 500 psi pressure courses in addition to pushing the fluid circulate velocities above class B (16 ft per second) to class C (24 feet 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 a hundred and fifty, 250 and 300 psi strain classes was printed in 1973. In 2011, size vary was increased to 6-in. via 60-in. These valves 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 standard, C517, was not printed till 2005. The 2005 measurement vary was three in. via 72 in. with a one hundred seventy five
Example butterfly valve differential pressure (top) and move rate control windows (bottom)
strain class for 3-in. through 12-in. sizes and one hundred fifty psi for the 14-in. via 72-in. The later editions (2009 and 2016) haven’t increased the valve sizes or stress lessons. The addition of the A velocity designation (8 fps) was added in the 2017 version. 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 by way of 1,500 mm), C522, is underneath development. This normal will embody the identical a hundred and fifty, 250 and 300 psi pressure courses and the identical fluid velocity designation of “D” (maximum 35 toes per second) as the present C507 ball valve normal.
In basic, all of the valve sizes, move rates and pressures have increased because the AWWA standard’s inception.
COMPONENTS OF OPERATING TORQUE
AWWA Manual M49 identifies 10 elements that have an result on operating torque for quarter-turn valves. These elements fall into two basic classes: (1) passive or friction-based elements, and (2) energetic or dynamically generated parts. Because valve producers can’t know the precise piping system parameters when publishing torque values, revealed torques are typically restricted 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 other five elements are impacted by system parameters such as valve orientation, media and flow velocity. The parts that make up active torque embody:
Active torque parts:
Disc weight and middle of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When contemplating all these varied active torque elements, it is potential for the precise working torque to exceed the valve manufacturer’s published torque values.
WHY IS M49 MORE IMPORTANT TODAY?
Although quarter-turn valves have been used within the waterworks business for a century, they’re being exposed to greater service strain and flow rate service conditions. Since the quarter-turn valve’s closure member is all the time located within the flowing fluid, these higher 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 physique as it reacts to all the fluid pressures and fluid circulate dynamic situations.
In addition to the increased service situations, the valve sizes are additionally increasing. The dynamic circumstances of the flowing fluid have larger impact on the bigger valve sizes. Therefore, the fluid dynamic results become extra essential than static differential pressure and friction loads. Valves may be leak and hydrostatically shell tested throughout fabrication. However, the full fluid circulate situations cannot be replicated earlier than site set up.
Because of the development for increased valve sizes and increased working conditions, it is more and more important for the system designer, operator and owner of quarter-turn valves to higher understand the influence of system and fluid dynamics have on valve choice, building and use.
The AWWA Manual of Standard Practice M forty nine is dedicated to the understanding of quarter-turn valves including operating torque requirements, differential stress, move circumstances, throttling, cavitation and system set up variations that immediately affect the operation and profitable use of quarter-turn valves in waterworks methods.
AWWA MANUAL OF STANDARD PRACTICE M49 4TH EDITION DEVELOPMENTS
The fourth edition of M49 is being developed to include the changes within the quarter-turn valve product requirements and installed system interactions. A new chapter might be devoted to methods of control valve sizing for fluid move, pressure management and throttling in waterworks service. This methodology includes explanations on the usage of strain, circulate rate and cavitation graphical windows to offer the user a thorough picture of valve performance over a variety of anticipated system operating circumstances.
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 previously labored at Val-Matic as Director of Engineering. He has participated in requirements developing organizations, together with AWWA, MSS, ASSE and API. Dalton holds BS and MS degrees 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 each 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) in the improvement of their quarter-turn valve performance prediction strategies for the nuclear energy trade.
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