Valve manufacturers publish torques for his or her merchandise in order that actuation and mounting hardware may be correctly selected. However, published torque values usually symbolize solely the seating or unseating torque for a valve at its rated pressure. While these are essential values for reference, published valve torques do not account for actual installation and working characteristics. In order to find out the actual operating torque for valves, it’s necessary to know the parameters of the piping systems into which they are installed. Factors similar to set up orientation, direction of flow and fluid velocity of the media all influence the precise operating torque of valves.
Trunnion mounted ball valve operated by a single performing spring return actuator. Photo credit score: Val-Matic
The American Water Works Association (AWWA) publishes detailed info 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 published in 2001 with torque calculations for butterfly valves, AWWA M49 is currently in its third version. In addition to information on butterfly valves, the current edition also contains working torque calculations for other quarter-turn valves together with plug valves and ball valves. Overall, this manual identifies 10 elements of torque that can 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 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 classes. In 1966 the 50 and 125 psi pressure courses have been increased to 75 and 150 psi. The 250 psi strain class was added in 2000. The 78-in. and larger butterfly valve commonplace, C516, was first revealed in 2010 with 25, 50, 75 and one hundred fifty psi strain lessons with the 250 psi class added in 2014. The high-performance butterfly valve commonplace was published in 2018 and consists of 275 and 500 psi stress courses in addition to pushing the fluid circulate velocities above class B (16 toes per second) to class C (24 ft per second) and sophistication D (35 ft per second).
The first AWWA quarter-turn ball valve standard, C507, for 6-in. via 48-in. ball valves in a hundred and fifty, 250 and 300 psi pressure courses was revealed in 1973. In 2011, size range was increased to 6-in. by way of 60-in. These valves have at all times been designed for 35 ft per second (fps) most 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 published till 2005. The 2005 dimension vary was 3 in. through seventy two in. with a a hundred seventy five
Example butterfly valve differential stress (top) and move price control windows (bottom)
pressure class for 3-in. through 12-in. sizes and a hundred and fifty psi for the 14-in. via 72-in. The later editions (2009 and 2016) have not increased the valve sizes or pressure classes. The addition of the A velocity designation (8 fps) was added within the 2017 version. This valve is primarily used 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 through 1,500 mm), C522, is beneath improvement. This normal will encompass the same a hundred and fifty, 250 and 300 psi stress classes and the same fluid velocity designation of “D” (maximum 35 toes per second) as the present C507 ball valve normal.
In เกจวัดแรงดูด , all the valve sizes, flow charges and pressures have elevated 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 parts fall into two general classes: (1) passive or friction-based parts, and (2) lively or dynamically generated components. Because valve manufacturers can not know the actual piping system parameters when publishing torque values, printed torques are usually limited to the five elements of passive or friction-based elements. These embrace:
Passive torque elements:
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 such as valve orientation, media and move velocity. The parts that make up lively torque embody:
Active torque parts:
Disc weight and middle of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When considering all these varied active torque parts, it’s attainable for the precise operating 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 uncovered to greater service pressure and flow price service conditions. Since the quarter-turn valve’s closure member is at all times located within the flowing fluid, these higher service circumstances immediately influence the valve. Operation of these valves require an actuator to rotate and/or hold the closure member inside the valve’s physique because it reacts to all the fluid pressures and fluid circulate dynamic situations.
In addition to the elevated service circumstances, the valve sizes are additionally increasing. The dynamic conditions of the flowing fluid have higher effect on the larger valve sizes. Therefore, the fluid dynamic effects become more necessary than static differential strain and friction masses. Valves can be leak and hydrostatically shell tested during fabrication. However, the total fluid move circumstances cannot be replicated before web site set up.
Because of the pattern for increased valve sizes and elevated working circumstances, it is increasingly essential for the system designer, operator and owner of quarter-turn valves to raised perceive the influence of system and fluid dynamics have on valve selection, construction and use.
The AWWA Manual of Standard Practice M 49 is dedicated to the understanding of quarter-turn valves including operating torque requirements, differential pressure, flow circumstances, throttling, cavitation and system set up differences that immediately affect the operation and successful use of quarter-turn valves in waterworks systems.
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 put in system interactions. A new chapter shall be dedicated to methods of control valve sizing for fluid move, pressure control and throttling in waterworks service. This methodology contains explanations on using strain, move fee and cavitation graphical home windows to supply the user a radical picture of valve efficiency over a variety of anticipated system operating situations.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton started 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 labored 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 levels 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 both 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 worked with the Electric Power Research Institute (EPRI) within the improvement of their quarter-turn valve performance prediction methods for the nuclear power trade.
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