Valve producers publish torques for his or her products in order that actuation and mounting hardware can be correctly selected. However, revealed torque values often characterize only the seating or unseating torque for a valve at its rated pressure. While these are necessary values for reference, revealed valve torques do not account for precise installation and working traits. In order to find out the precise operating torque for valves, it’s essential to understand the parameters of the piping techniques into which they’re installed. เกจวัดแรงดันดิจิตอลราคา as installation orientation, direction of flow and fluid velocity of the media all influence the actual working torque of valves.
Trunnion 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 working torques for quarter-turn valves. This information 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 at present in its third edition. In addition to data on butterfly valves, the current edition also consists of operating 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.
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AWWA QUARTER-TURN VALVE HISTORY
The first AWWA quarter-turn valve standard for 3-in. through 72-in. butterfly valves, C504, was revealed in 1958 with 25, 50 and one hundred twenty five psi pressure lessons. In 1966 the 50 and one 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 printed in 2010 with 25, 50, 75 and a hundred and fifty psi pressure lessons with the 250 psi class added in 2014. The high-performance butterfly valve standard was revealed in 2018 and consists of 275 and 500 psi pressure lessons in addition to pushing the fluid circulate velocities above class B (16 feet per second) to class C (24 feet per second) and sophistication 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 a hundred and fifty, 250 and 300 psi pressure classes was revealed in 1973. In 2011, measurement range was increased to 6-in. through 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 standard 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 measurement range was three in. by way of seventy two in. with a one hundred seventy five
Example butterfly valve differential pressure (top) and flow fee control home windows (bottom)
strain class for 3-in. through 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 lessons. The addition of the A velocity designation (8 fps) was added in the 2017 version. This valve is primarily utilized in wastewater service where 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 standard will embody the identical a hundred and fifty, 250 and 300 psi pressure courses and the same fluid velocity designation of “D” (maximum 35 ft per second) as the current C507 ball valve commonplace.
In basic, all the valve sizes, flow rates and pressures have increased for the reason that AWWA standard’s inception.
COMPONENTS OF OPERATING TORQUE
AWWA Manual M49 identifies 10 elements that affect working torque for quarter-turn valves. These parts fall into two basic categories: (1) passive or friction-based components, and (2) energetic or dynamically generated components. Because valve manufacturers can not know the actual piping system parameters when publishing torque values, revealed torques are generally limited to the five elements of passive or friction-based components. These embrace:
Passive torque elements:
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 corresponding to valve orientation, media and circulate velocity. The elements that make up active torque embrace:
Active torque elements:
Disc weight and center of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When considering all these numerous active torque components, it’s attainable for the precise operating torque to exceed the valve manufacturer’s printed torque values.
WHY IS M49 MORE IMPORTANT TODAY?
Although quarter-turn valves have been used in the waterworks business for a century, they are being exposed to greater service strain and move price service conditions. Since the quarter-turn valve’s closure member is all the time located within the flowing fluid, these larger service situations directly impression the valve. Operation of those valves require an actuator to rotate and/or maintain the closure member within the valve’s body as it reacts to all the fluid pressures and fluid circulate dynamic conditions.
In addition to the elevated service situations, the valve sizes are also growing. The dynamic situations of the flowing fluid have larger impact on the bigger valve sizes. Therefore, the fluid dynamic effects become extra essential than static differential stress and friction loads. Valves can be leak and hydrostatically shell examined throughout fabrication. However, the full fluid flow circumstances can’t be replicated before web site set up.
Because of the pattern for increased valve sizes and increased operating situations, it is more and more important for the system designer, operator and proprietor of quarter-turn valves to better understand the impact of system and fluid dynamics have on valve selection, construction and use.
The AWWA Manual of Standard Practice M forty nine is dedicated to the understanding of quarter-turn valves together with working torque necessities, differential strain, move conditions, throttling, cavitation and system set up variations that immediately influence the operation and profitable use of quarter-turn valves in waterworks systems.
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 standards and put in system interactions. A new chapter shall be devoted to methods of management valve sizing for fluid circulate, pressure control and throttling in waterworks service. This methodology contains explanations on the use of stress, move rate and cavitation graphical home windows to provide the person a thorough image of valve performance over a spread of anticipated system working situations.
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 worked at Val-Matic as Director of Engineering. He has participated in standards developing organizations, including 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 concerned in quarter-turn valve and actuator engineering and design for 50 years and has been an energetic member of each 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 labored with the Electric Power Research Institute (EPRI) in the development of their quarter-turn valve efficiency prediction strategies for the nuclear power industry.
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