Valve manufacturers publish torques for their merchandise in order that actuation and mounting hardware could be properly chosen. However, printed torque values often represent only the seating or unseating torque for a valve at its rated strain. While these are necessary values for reference, revealed valve torques don’t account for actual set up and operating traits. In order to discover out the actual operating torque for valves, it’s needed to grasp the parameters of the piping techniques into which they’re installed. Factors similar to installation orientation, course of circulate and fluid velocity of the media all influence the actual 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 data on calculating working torques for quarter-turn valves. This info seems in AWWA Manual M49 Quarter-Turn Valves: Head Loss, Torque, and Cavitation Analysis. Originally printed in 2001 with torque calculations for butterfly valves, AWWA M49 is at present in its third edition. In addition to info on butterfly valves, the present edition additionally consists of operating torque calculations for other quarter-turn valves including plug valves and ball valves. Overall, this manual identifies 10 elements of torque that may contribute to a quarter-turn valve’s working torque.
Example torque calculation abstract graph
AWWA QUARTER-TURN VALVE HISTORY
The first AWWA quarter-turn valve standard for 3-in. by way of 72-in. butterfly valves, C504, was printed in 1958 with 25, 50 and one hundred twenty five psi strain courses. In 1966 the 50 and one hundred twenty five psi stress classes have been elevated to seventy five and one hundred fifty psi. The 250 psi stress class was added in 2000. The 78-in. and bigger butterfly valve normal, C516, was first published in 2010 with 25, 50, 75 and 150 psi stress classes with the 250 psi class added in 2014. The high-performance butterfly valve normal was revealed in 2018 and includes 275 and 500 psi stress courses as properly as pushing the fluid flow velocities above class B (16 feet per second) to class C (24 toes per second) and class D (35 ft per second).
The first AWWA quarter-turn ball valve commonplace, C507, for 6-in. through 48-in. ball valves in a hundred and fifty, 250 and 300 psi pressure lessons was revealed in 1973. In 2011, size vary was increased to 6-in. by way of 60-in. These valves have at all times been designed for 35 ft per second (fps) maximum fluid velocity. เกจวัดแรงดันไฟฟ้า 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 first a AWWA quarter-turn valve standard, C517, was not revealed till 2005. The 2005 dimension vary was three in. via seventy two in. with a a hundred seventy five
Example butterfly valve differential strain (top) and flow rate control windows (bottom)
strain class for 3-in. by way of 12-in. sizes and one hundred fifty psi for the 14-in. by way of 72-in. The later editions (2009 and 2016) have not elevated the valve sizes or pressure courses. The addition of the A velocity designation (8 fps) was added within 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 acknowledged in 2018 and the AWWA Rotary Cone Valves, 6 Inch Through 60 Inch (150 mm via 1,500 mm), C522, is under development. This standard will embody the identical 150, 250 and 300 psi stress courses and the same fluid velocity designation of “D” (maximum 35 feet per second) as the present C507 ball valve normal.
In basic, all of the valve sizes, circulate rates and pressures have increased for the explanation that AWWA standard’s inception.
COMPONENTS OF OPERATING TORQUE
AWWA Manual M49 identifies 10 components that affect working torque for quarter-turn valves. These components fall into two basic classes: (1) passive or friction-based parts, and (2) active or dynamically generated elements. Because valve manufacturers cannot know the actual piping system parameters when publishing torque values, printed torques are typically restricted to the 5 parts of passive or friction-based parts. These include:
Passive torque components:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The different five components are impacted by system parameters corresponding to valve orientation, media and move velocity. The elements that make up energetic torque embrace:
Active torque components:
Disc weight and heart of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When contemplating all these varied lively torque components, it’s possible 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 in the waterworks business for a century, they’re being exposed to larger service stress and circulate rate service situations. Since the quarter-turn valve’s closure member is always situated within the flowing fluid, these larger service circumstances 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 move dynamic situations.
In addition to the elevated service circumstances, the valve sizes are additionally growing. The dynamic circumstances of the flowing fluid have greater effect on the larger valve sizes. Therefore, the fluid dynamic effects become more necessary than static differential strain and friction hundreds. Valves could be leak and hydrostatically shell examined during fabrication. However, the total fluid flow circumstances cannot be replicated earlier than site set up.
Because of the development for elevated valve sizes and elevated operating circumstances, it is increasingly essential 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, building and use.
The AWWA Manual of Standard Practice M 49 is devoted to the understanding of quarter-turn valves including operating torque necessities, differential pressure, flow conditions, throttling, cavitation and system installation variations that directly affect the operation and profitable use of quarter-turn valves in waterworks methods.
AWWA MANUAL OF STANDARD PRACTICE M49 4TH EDITION DEVELOPMENTS
The fourth version of M49 is being developed to incorporate the adjustments within the quarter-turn valve product requirements and installed system interactions. A new chapter shall be devoted to methods of control valve sizing for fluid move, pressure control and throttling in waterworks service. This methodology includes explanations on the use of strain, flow rate and cavitation graphical windows to offer the person an intensive picture of valve efficiency over a spread of anticipated system operating situations.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton began his career as a consulting engineer within the waterworks trade 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 growing 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 involved in quarter-turn valve and actuator engineering and design for 50 years and has been an active 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 labored with the Electric Power Research Institute (EPRI) within the development of their quarter-turn valve performance prediction methods for the nuclear energy industry.
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