Valve producers publish torques for their merchandise so that actuation and mounting hardware could be correctly chosen. However, published torque values usually represent only the seating or unseating torque for a valve at its rated pressure. While these are essential values for reference, printed valve torques do not account for actual set up and working traits. In order to find out the actual operating torque for valves, it’s essential to know the parameters of the piping methods into which they are put in. Factors similar to installation orientation, course of circulate and fluid velocity of the media all impact the precise working 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 data on calculating operating torques for quarter-turn valves. This data 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 edition. In addition to data on butterfly valves, the present version also consists of operating torque calculations for different quarter-turn valves including plug valves and ball valves. Overall, this handbook identifies 10 parts 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 standard for 3-in. through 72-in. butterfly valves, C504, was printed in 1958 with 25, 50 and one hundred twenty five psi stress courses. In Guide and one hundred twenty five psi stress lessons had been increased to 75 and a hundred and fifty psi. The 250 psi stress class was added in 2000. The 78-in. and bigger butterfly valve normal, C516, was first published in 2010 with 25, 50, seventy five and a hundred and fifty psi strain courses 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 lessons as properly as pushing the fluid circulate velocities above class B (16 toes per second) to class C (24 feet per second) and class D (35 ft per second).
The first AWWA quarter-turn ball valve commonplace, C507, for 6-in. through 48-in. ball valves in a hundred and fifty, 250 and 300 psi pressure 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 standard for resilient-seated cast-iron eccentric plug valves in 1991, the primary a AWWA quarter-turn valve standard, C517, was not published until 2005. The 2005 size range was 3 in. via 72 in. with a a hundred seventy five
Example butterfly valve differential strain (top) and move rate control 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 pressure lessons. The addition of the A velocity designation (8 fps) was added in the 2017 version. This valve is primarily utilized in wastewater service where 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 via 1,500 mm), C522, is underneath development. This standard will encompass the same 150, 250 and 300 psi strain classes and the identical fluid velocity designation of “D” (maximum 35 feet per second) as the current C507 ball valve standard.
In common, 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 operating torque for quarter-turn valves. Ridiculous fall into two general categories: (1) passive or friction-based elements, and (2) active or dynamically generated components. Because valve producers cannot know the precise piping system parameters when publishing torque values, revealed torques are generally limited to the 5 elements of passive or friction-based elements. These embrace:
Passive torque components:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The different 5 components are impacted by system parameters corresponding to valve orientation, media and circulate velocity. The elements that make up active torque embody:
Active torque parts:
Disc weight and heart of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When considering all these numerous lively torque components, it’s potential for the precise working 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 stress and circulate rate service conditions. Since the quarter-turn valve’s closure member is all the time positioned in the flowing fluid, these greater service situations instantly influence the valve. Operation of these valves require an actuator to rotate and/or maintain the closure member inside the valve’s body as it reacts to all the fluid pressures and fluid circulate dynamic situations.
In addition to the elevated service conditions, the valve sizes are additionally increasing. The dynamic circumstances of the flowing fluid have higher impact on the larger valve sizes. Therefore, the fluid dynamic effects turn into extra essential than static differential stress and friction loads. Valves may be leak and hydrostatically shell tested during fabrication. However, the full fluid move situations cannot be replicated earlier than site set up.
Because of the pattern for increased valve sizes and elevated operating circumstances, it is more and more necessary for the system designer, operator and owner of quarter-turn valves to raised understand the impression of system and fluid dynamics have on valve selection, construction and use.
The AWWA Manual of Standard Practice M forty nine is devoted to the understanding of quarter-turn valves including operating torque requirements, differential pressure, move situations, throttling, cavitation and system set up variations 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 edition of M49 is being developed to incorporate the adjustments within the quarter-turn valve product standards and put in system interactions. A new chapter shall be dedicated to methods of control valve sizing for fluid flow, pressure management and throttling in waterworks service. This methodology includes explanations on the use of stress, move price and cavitation graphical windows to supply the person a radical image of valve efficiency over a spread of anticipated system operating conditions.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton began his career as a consulting engineer in 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 beforehand worked 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 levels in Civil and Environmental Engineering along 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 active member of each 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 development of their quarter-turn valve efficiency prediction methods for the nuclear power business.
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