Valve manufacturers publish torques for their products in order that actuation and mounting hardware can be correctly selected. However, published torque values often characterize solely the seating or unseating torque for a valve at its rated pressure. While these are essential values for reference, printed valve torques don’t account for precise set up and operating traits. In order to determine the actual operating torque for valves, it is needed to grasp the parameters of the piping systems into which they’re installed. Factors corresponding to installation orientation, course of flow and fluid velocity of the media all impact the precise operating torque of valves.
Trunnion mounted ball valve operated by a single appearing spring return actuator. Photo credit score: Val-Matic
The American Water Works Association (AWWA) publishes detailed info 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 published in pressure gauge ออก หลัง with torque calculations for butterfly valves, AWWA M49 is currently in its third edition. In addition to info on butterfly valves, the current version also contains working torque calculations for other quarter-turn valves including plug valves and ball valves. Overall, this manual identifies 10 components of torque that can contribute to a quarter-turn valve’s operating torque.
Example torque calculation abstract graph
AWWA QUARTER-TURN VALVE HISTORY
The first AWWA quarter-turn valve normal for 3-in. through 72-in. butterfly valves, C504, was printed in 1958 with 25, 50 and a hundred twenty five psi strain courses. In 1966 the 50 and one hundred twenty five psi strain lessons were elevated to 75 and 150 psi. The 250 psi pressure class was added in 2000. The 78-in. and larger butterfly valve standard, C516, was first published in 2010 with 25, 50, 75 and 150 psi pressure lessons with the 250 psi class added in 2014. The high-performance butterfly valve standard was revealed in 2018 and consists of 275 and 500 psi pressure courses in addition to pushing the fluid flow velocities above class B (16 feet per second) to class C (24 feet per second) and class D (35 toes 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 classes was published in 1973. In 2011, dimension range was increased to 6-in. through 60-in. These valves have all the time 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 standard for resilient-seated cast-iron eccentric plug valves in 1991, the primary a AWWA quarter-turn valve commonplace, C517, was not published until 2005. The 2005 dimension range was three in. via 72 in. with a one hundred seventy five
Example butterfly valve differential strain (top) and circulate fee management home windows (bottom)
pressure class for 3-in. via 12-in. sizes and a hundred and fifty psi for the 14-in. through 72-in. The later editions (2009 and 2016) have not elevated 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 where pressures and fluid velocities are maintained at decrease 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 growth. This standard will encompass the identical a hundred and fifty, 250 and 300 psi strain lessons and the identical fluid velocity designation of “D” (maximum 35 feet per second) as the present C507 ball valve normal.
In basic, all of the valve sizes, flow charges and pressures have elevated for the reason that AWWA standard’s inception.
COMPONENTS OF OPERATING TORQUE
AWWA Manual M49 identifies 10 elements that have an effect on operating torque for quarter-turn valves. These elements fall into two common categories: (1) passive or friction-based elements, and (2) lively or dynamically generated components. Because valve producers cannot know the precise piping system parameters when publishing torque values, published torques are typically restricted to the 5 parts of passive or friction-based parts. These embrace:
Passive torque parts:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The other five parts are impacted by system parameters corresponding to valve orientation, media and move velocity. The parts that make up active torque include:
Active torque elements:
Disc weight and middle of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When contemplating all these varied lively torque parts, it’s attainable for the actual working torque to exceed the valve manufacturer’s printed torque values.
WHY IS M49 MORE IMPORTANT TODAY?
Although quarter-turn valves have been used in the waterworks industry for a century, they’re being exposed to higher service stress and flow fee service circumstances. Since the quarter-turn valve’s closure member is always situated in the flowing fluid, these greater service circumstances immediately impact the valve. Operation of those valves require an actuator to rotate and/or maintain the closure member inside the valve’s physique as it reacts to all of the fluid pressures and fluid move dynamic conditions.
In addition to the increased service circumstances, the valve sizes are additionally increasing. The dynamic circumstances of the flowing fluid have greater impact on the bigger valve sizes. Therefore, the fluid dynamic effects turn into more important than static differential pressure and friction loads. Valves may be leak and hydrostatically shell tested during fabrication. However, the complete fluid flow situations can’t be replicated earlier than site set up.
Because of the trend for increased valve sizes and increased working conditions, it’s more and more essential for the system designer, operator and proprietor of quarter-turn valves to higher understand the influence of system and fluid dynamics have on valve selection, development 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 strain, circulate conditions, throttling, cavitation and system installation variations that instantly 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 incorporate the changes in the quarter-turn valve product requirements and put in system interactions. A new chapter shall be dedicated to methods of management valve sizing for fluid circulate, pressure management and throttling in waterworks service. This methodology contains explanations on the use of stress, flow rate and cavitation graphical windows to provide the person an intensive picture of valve efficiency over a spread of anticipated system operating circumstances.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton began his profession as a consulting engineer in 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 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 active 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.” 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 energy business.
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