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Valve producers publish torques for his or her merchandise in order that actuation and mounting hardware may be properly selected. However, revealed torque values typically represent solely the seating or unseating torque for a valve at its rated strain. While these are essential values for reference, revealed valve torques do not account for precise installation and operating characteristics. In order to determine the precise operating torque for valves, it’s needed to grasp the parameters of the piping systems into which they’re installed. เครื่องมือที่ใช้วัดความดันเลือด corresponding to set up orientation, course of circulate 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 score: Val-Matic
The American Water Works Association (AWWA) publishes detailed data on calculating working 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 at present in its third version. In addition to info on butterfly valves, the current version also consists of working torque calculations for other quarter-turn valves including plug valves and ball valves. Overall, this manual identifies 10 components of torque that may 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 published in 1958 with 25, 50 and 125 psi stress lessons. In 1966 the 50 and a hundred twenty five psi stress courses had been increased to 75 and one hundred fifty psi. The 250 psi strain class was added in 2000. The 78-in. and larger butterfly valve normal, C516, was first revealed in 2010 with 25, 50, seventy five and 150 psi pressure classes with the 250 psi class added in 2014. The high-performance butterfly valve commonplace was printed in 2018 and consists of 275 and 500 psi stress lessons as properly as pushing the fluid flow velocities above class B (16 ft per second) to class C (24 ft per second) and class D (35 ft per second).
The first AWWA quarter-turn ball valve normal, C507, for 6-in. through 48-in. ball valves in one hundred fifty, 250 and 300 psi strain courses was published in 1973. In 2011, dimension vary was elevated 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 primary a AWWA quarter-turn valve normal, C517, was not printed until 2005. The 2005 dimension range was 3 in. via 72 in. with a one hundred seventy five
Example butterfly valve differential strain (top) and flow price control home windows (bottom)
pressure class for 3-in. via 12-in. sizes and a hundred and fifty psi for the 14-in. through 72-in. The later editions (2009 and 2016) have not increased the valve sizes or stress courses. The addition of the A velocity designation (8 fps) was added in the 2017 version. This valve is primarily used in wastewater service the place pressures and fluid velocities are maintained at lower 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 under growth. This commonplace will encompass the same 150, 250 and 300 psi stress classes and the same 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 elevated since the AWWA standard’s inception.
AWWA Manual M49 identifies 10 elements that affect operating torque for quarter-turn valves. These components fall into two basic classes: (1) passive or friction-based elements, and (2) lively or dynamically generated parts. Because valve producers can’t know the precise piping system parameters when publishing torque values, revealed torques are usually restricted to the five components of passive or friction-based components. These embody:
Passive torque parts:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The other 5 parts are impacted by system parameters similar to valve orientation, media and move velocity. The parts that make up energetic 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 various lively torque parts, it is attainable for the actual operating torque to exceed the valve manufacturer’s printed torque values.
Although quarter-turn valves have been used in the waterworks trade for a century, they are being exposed to larger service pressure and circulate fee service situations. Since the quarter-turn valve’s closure member is all the time situated within the flowing fluid, these higher service conditions immediately impact the valve. Operation of these valves require an actuator to rotate and/or maintain the closure member throughout the valve’s body because it reacts to all the fluid pressures and fluid move dynamic conditions.
In addition to the elevated service circumstances, the valve sizes are additionally increasing. The dynamic situations of the flowing fluid have larger impact on the bigger valve sizes. Therefore, the fluid dynamic effects become more necessary than static differential pressure and friction hundreds. Valves can be leak and hydrostatically shell examined during fabrication. However, the full fluid flow circumstances can’t be replicated earlier than web site set up.
Because of the development for increased valve sizes and increased operating situations, it is more and more important for the system designer, operator and owner of quarter-turn valves to raised perceive the impression of system and fluid dynamics have on valve choice, building and use.
The AWWA Manual of Standard Practice M 49 is devoted to the understanding of quarter-turn valves including working torque requirements, differential pressure, circulate situations, throttling, cavitation and system installation differences that directly affect the operation and successful use of quarter-turn valves in waterworks techniques.
The fourth edition of M49 is being developed to incorporate the modifications in the quarter-turn valve product requirements and put in system interactions. A new chapter might be dedicated to strategies of management valve sizing for fluid circulate, stress management and throttling in waterworks service. This methodology consists of explanations on the utilization of stress, move fee and cavitation graphical windows to supply the person a radical picture of valve performance over a spread of anticipated system working circumstances.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton began his career as a consulting engineer in 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 previously worked at Val-Matic as Director of Engineering. He has participated in requirements creating 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 additionally worked with the Electric Power Research Institute (EPRI) in the growth of their quarter-turn valve performance prediction methods for the nuclear power trade.