Valve producers publish torques for their merchandise so that actuation and mounting hardware may be correctly selected. However, revealed torque values often symbolize solely the seating or unseating torque for a valve at its rated pressure. While these are important values for reference, published valve torques do not account for precise set up and operating traits. In order to determine the precise working torque for valves, it is essential to understand the parameters of the piping systems into which they are installed. Factors such as installation orientation, path of flow 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 information on calculating working torques for quarter-turn valves. This info 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 currently in its third version. In addition to data on butterfly valves, the present version additionally consists of operating torque calculations for other quarter-turn valves together with plug valves and ball valves. Overall, this handbook identifies 10 parts 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. via 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 125 psi strain courses were elevated to 75 and one hundred fifty psi. The 250 psi stress class was added in 2000. The 78-in. and bigger butterfly valve standard, C516, was first published in 2010 with 25, 50, seventy five and a hundred and fifty psi pressure lessons with the 250 psi class added in 2014. The high-performance butterfly valve normal was revealed in 2018 and contains 275 and 500 psi strain classes in addition to pushing the fluid flow velocities above class B (16 ft per second) to class C (24 toes per second) and sophistication D (35 feet per second).
The first AWWA quarter-turn ball valve standard, C507, for 6-in. via 48-in. ball valves in one hundred fifty, 250 and 300 psi stress lessons was revealed in 1973. In 2011, dimension range was elevated to 6-in. through 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 till 2005. The 2005 measurement range was 3 in. through seventy two in. with a one hundred seventy five
Example butterfly valve differential stress (top) and move fee management home windows (bottom)
strain class for 3-in. via 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 increased the valve sizes or stress classes. The addition of the A velocity designation (8 fps) was added in the 2017 edition. This valve is primarily utilized in wastewater service the place pressures and fluid velocities are maintained at lower values.
The want for a rotary cone valve was recognized in 2018 and the AWWA Rotary Cone Valves, 6 Inch Through 60 Inch (150 mm via 1,500 mm), C522, is underneath development. This commonplace will encompass the same 150, 250 and 300 psi pressure courses and the identical fluid velocity designation of “D” (maximum 35 ft per second) as the present C507 ball valve standard.
In general, all of the valve sizes, circulate charges and pressures have elevated because the AWWA standard’s inception.
COMPONENTS OF OPERATING TORQUE
AWWA Manual M49 identifies 10 components that have an result on working torque for quarter-turn valves. These components fall into two common categories: (1) passive or friction-based components, and (2) active or dynamically generated components. Because valve manufacturers can’t know the precise piping system parameters when publishing torque values, printed torques are generally restricted to the five components of passive or friction-based components. These include:
Passive torque elements:
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 such as valve orientation, media and flow velocity. The components that make up energetic torque embrace:
Active torque components:
Disc weight and heart of gravity torque
Disc buoyancy torque
Fluid dynamic torque
Hydrostatic unbalance torque
When considering all these varied active torque parts, it is potential for the actual working torque to exceed the valve manufacturer’s published torque values.
WHY IS M49 MORE IMPORTANT TODAY?
Although quarter-turn valves have been used within the waterworks industry for a century, they’re being uncovered to greater service pressure and move rate service conditions. Since the quarter-turn valve’s closure member is always positioned within the flowing fluid, these greater service circumstances instantly impression the valve. Operation of these valves require an actuator to rotate and/or maintain the closure member inside the valve’s body because it reacts to all the fluid pressures and fluid move dynamic circumstances.
In addition to the increased service circumstances, the valve sizes are additionally rising. The dynamic situations of the flowing fluid have higher impact on the larger valve sizes. Therefore, the fluid dynamic effects become extra essential than static differential strain and friction masses. Valves can be leak and hydrostatically shell tested throughout fabrication. However, the complete fluid flow conditions cannot be replicated earlier than site set up.
Because of the pattern for increased valve sizes and increased operating conditions, it is more and more necessary for the system designer, operator and proprietor of quarter-turn valves to higher perceive the impression of system and fluid dynamics have on valve selection, building and use.
The AWWA Manual of Standard Practice M forty nine is dedicated to the understanding of quarter-turn valves together with working torque requirements, differential pressure, circulate circumstances, throttling, cavitation and system set up differences that immediately affect the operation and successful use of quarter-turn valves in waterworks techniques.
AWWA MANUAL OF STANDARD PRACTICE M49 4TH EDITION DEVELOPMENTS
The fourth version of M49 is being developed to include the adjustments in the quarter-turn valve product standards and put in system interactions. A new chapter will be devoted to methods of control valve sizing for fluid move, strain control and throttling in waterworks service. This methodology consists of explanations on the use of pressure, circulate price and cavitation graphical windows to supply the person an intensive picture of valve performance over a range of anticipated system working situations.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton started his profession 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 standards creating 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 lively 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.” ที่วัดแรงดัน has also labored with the Electric Power Research Institute (EPRI) within the improvement of their quarter-turn valve efficiency prediction strategies for the nuclear power trade.