Valve manufacturers publish torques for their merchandise in order that actuation and mounting hardware can be correctly selected. However, revealed torque values typically symbolize only the seating or unseating torque for a valve at its rated strain. While these are important values for reference, published valve torques don’t account for actual set up and working traits. In order to discover out the actual working torque for valves, it is needed to know the parameters of the piping methods into which they are put in. Factors corresponding to installation orientation, path of flow 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: Val-Matic
The American Water Works Association (AWWA) publishes detailed info on calculating working torques for quarter-turn valves. This information 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 presently in its third version. In addition to information on butterfly valves, the present version also consists of operating torque calculations for other 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 summary graph
The first AWWA quarter-turn valve normal for 3-in. by way of 72-in. butterfly valves, C504, was printed in 1958 with 25, 50 and a hundred twenty five psi stress courses. In 1966 the 50 and 125 psi pressure courses had been elevated 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 published in 2010 with 25, 50, 75 and 150 psi pressure courses with the 250 psi class added in 2014. The high-performance butterfly valve normal was printed in 2018 and contains 275 and 500 psi pressure courses as well as pushing the fluid move 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 commonplace, C507, for 6-in. via 48-in. ball valves in one hundred fifty, 250 and 300 psi pressure courses was revealed in 1973. In 2011, dimension range was increased to 6-in. via 60-in. These valves have at all times 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 normal for resilient-seated cast-iron eccentric plug valves in 1991, the primary a AWWA quarter-turn valve standard, C517, was not printed until 2005. The 2005 size vary was three in. through seventy two in. with a one hundred seventy five
Example butterfly valve differential pressure (top) and flow fee management windows (bottom)
pressure class for 3-in. by way of 12-in. sizes and 150 psi for the 14-in. by way of 72-in. The later editions (2009 and 2016) haven’t elevated the valve sizes or strain classes. 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 decrease values.
เกจวัดความดันแก๊ส 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 growth. This normal will encompass the same one hundred fifty, 250 and 300 psi pressure classes and the same fluid velocity designation of “D” (maximum 35 toes per second) as the present C507 ball valve standard.
In general, all of the valve sizes, move rates and pressures have increased because the AWWA standard’s inception.
AWWA Manual M49 identifies 10 parts that affect working torque for quarter-turn valves. These parts fall into two common classes: (1) passive or friction-based elements, and (2) lively or dynamically generated elements. Because valve producers cannot know the actual piping system parameters when publishing torque values, published torques are generally limited to the 5 parts 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 different five parts are impacted by system parameters similar to valve orientation, media and circulate velocity. The elements that make up active torque include:
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 energetic torque components, it’s attainable for the precise operating torque to exceed the valve manufacturer’s printed torque values.
Although quarter-turn valves have been used within the waterworks industry for a century, they’re being uncovered to higher service stress and flow rate service situations. Since the quarter-turn valve’s closure member is all the time located in the flowing fluid, these greater service conditions instantly impact the valve. Operation of those valves require an actuator to rotate and/or hold the closure member throughout the valve’s body because it reacts to all of the fluid pressures and fluid circulate dynamic circumstances.
In addition to the increased service conditions, the valve sizes are additionally increasing. The dynamic situations of the flowing fluid have higher effect on the larger valve sizes. Therefore, the fluid dynamic effects turn out to be extra important than static differential strain and friction masses. Valves may be leak and hydrostatically shell examined during fabrication. However, the full fluid circulate situations cannot be replicated before web site installation.
Because of ความหมายของเครื่องวัดความดัน for increased valve sizes and elevated operating circumstances, it’s increasingly necessary for the system designer, operator and owner of quarter-turn valves to better perceive the impression of system and fluid dynamics have on valve choice, development 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 conditions, throttling, cavitation and system set up differences that immediately affect the operation and profitable use of quarter-turn valves in waterworks methods.
The fourth version of M49 is being developed to incorporate the adjustments within the quarter-turn valve product standards and installed system interactions. A new chapter might be devoted to methods of management valve sizing for fluid flow, pressure control and throttling in waterworks service. This methodology contains explanations on the use of pressure, move fee and cavitation graphical windows to provide the user an intensive picture of valve performance over a spread of anticipated system working conditions.
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About the Authors
Steve Dalton started his career as a consulting engineer within 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 beforehand worked at Val-Matic as Director of Engineering. He has participated in standards growing 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 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 worked with the Electric Power Research Institute (EPRI) within the growth of their quarter-turn valve performance prediction strategies for the nuclear power industry.