Valve manufacturers publish torques for his or her products so that actuation and mounting hardware could be correctly selected. However, published torque values often represent only the seating or unseating torque for a valve at its rated stress. While these are essential values for reference, printed valve torques do not account for actual installation and working characteristics. In order to discover out the actual operating torque for valves, it’s essential to understand the parameters of the piping methods into which they are installed. Factors similar to installation orientation, direction of move and fluid velocity of the media all impact 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 information on calculating operating torques for quarter-turn valves. This info seems 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 information on butterfly valves, the present version also includes working torque calculations for other quarter-turn valves including plug valves and ball valves. Overall, this guide identifies 10 elements of torque that can contribute to a quarter-turn valve’s operating torque.
Example torque calculation summary graph
The first AWWA quarter-turn valve standard for 3-in. via 72-in. butterfly valves, C504, was published in 1958 with 25, 50 and a hundred twenty five psi strain classes. In 1966 the 50 and a hundred twenty five psi strain lessons have been increased to 75 and a hundred and fifty psi. The 250 psi stress class was added in 2000. The 78-in. and larger butterfly valve commonplace, C516, was first published in 2010 with 25, 50, seventy five and one hundred fifty psi pressure courses with the 250 psi class added in 2014. The high-performance butterfly valve normal was printed in 2018 and consists of 275 and 500 psi pressure courses in addition to pushing the fluid flow velocities above class B (16 ft per second) to class C (24 ft per second) and class D (35 feet per second).
The first AWWA quarter-turn ball valve standard, C507, for 6-in. through 48-in. ball valves in a hundred and fifty, 250 and 300 psi strain courses was revealed in 1973. In 2011, size vary was elevated 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 commonplace for resilient-seated cast-iron eccentric plug valves in 1991, the primary a AWWA quarter-turn valve commonplace, C517, was not printed until 2005. The 2005 size range was 3 in. by way of 72 in. with a 175
Example butterfly valve differential pressure (top) and flow fee control windows (bottom)
strain class for 3-in. via 12-in. sizes and 150 psi for the 14-in. through 72-in. The later editions (2009 and 2016) haven’t elevated 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 utilized in wastewater service the place 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 through 1,500 mm), C522, is beneath improvement. This commonplace will encompass the same 150, 250 and 300 psi stress courses and the same fluid velocity designation of “D” (maximum 35 ft per second) as the present C507 ball valve normal.
In common, all of the valve sizes, move charges and pressures have increased since the AWWA standard’s inception.
AWWA Manual M49 identifies 10 components that affect operating torque for quarter-turn valves. These components fall into two general categories: (1) passive or friction-based parts, and (2) lively or dynamically generated components. Because valve producers can not know the actual piping system parameters when publishing torque values, revealed torques are generally limited to the 5 components of passive or friction-based components. pressure gauge หน้าปัด 4 นิ้ว :
Passive torque parts:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The different 5 elements are impacted by system parameters similar to valve orientation, media and circulate velocity. The elements that make up lively torque include:
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 numerous active torque elements, it is attainable for the actual working torque to exceed the valve manufacturer’s revealed torque values.
Although quarter-turn valves have been used within the waterworks industry for a century, they’re being uncovered to larger service stress and move rate service conditions. Since the quarter-turn valve’s closure member is all the time situated within the flowing fluid, these larger service circumstances instantly impact the valve. Operation of these valves require an actuator to rotate and/or hold the closure member within the valve’s physique as it reacts to all of the fluid pressures and fluid move dynamic circumstances.
In addition to the elevated service circumstances, the valve sizes are additionally growing. The dynamic conditions of the flowing fluid have higher effect on the bigger valve sizes. Therefore, the fluid dynamic effects become extra essential than static differential strain and friction loads. Valves may be leak and hydrostatically shell tested during fabrication. However, the complete fluid circulate circumstances can’t be replicated earlier than website set up.
Because of the trend for increased valve sizes and elevated working situations, it’s more and more essential for the system designer, operator and proprietor of quarter-turn valves to better perceive the impact of system and fluid dynamics have on valve choice, construction 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, circulate conditions, throttling, cavitation and system set up differences that directly influence the operation and successful use of quarter-turn valves in waterworks methods.
The fourth edition of M49 is being developed to incorporate the modifications in the quarter-turn valve product standards and put in system interactions. A new chapter might be dedicated to methods of control valve sizing for fluid circulate, stress management and throttling in waterworks service. This methodology consists of explanations on using strain, circulate rate and cavitation graphical windows to provide the consumer a radical picture of valve efficiency over a spread of anticipated system working situations.
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About the Authors
Steve Dalton began his profession as a consulting engineer within 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 beforehand labored 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 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 both 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 methods for the nuclear power industry.