Understanding Torque for Quarter-Turn Valves

Valve manufacturers publish torques for their products in order that actuation and mounting hardware could be properly chosen. However, revealed torque values typically characterize only the seating or unseating torque for a valve at its rated pressure. While these are necessary values for reference, revealed valve torques don’t account for actual installation and working characteristics. In order to discover out the actual operating torque for valves, it is essential to know the parameters of the piping methods into which they are put in. Factors such as set up orientation, direction of flow and fluid velocity of the media all impact the actual 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 information on calculating working torques for quarter-turn valves. This information appears 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 pressure gauge ลม to info on butterfly valves, the present version additionally includes operating torque calculations for different quarter-turn valves together with plug valves and ball valves. Overall, this handbook identifies 10 elements of torque that may contribute to a quarter-turn valve’s operating torque.
Example torque calculation abstract graph
The first AWWA quarter-turn valve standard for 3-in. by way of 72-in. butterfly valves, C504, was printed in 1958 with 25, 50 and a hundred twenty five psi strain lessons. In 1966 the 50 and one hundred twenty five psi stress courses had been elevated to seventy five and 150 psi. The 250 psi stress class was added in 2000. The 78-in. and bigger butterfly valve commonplace, C516, was first printed in 2010 with 25, 50, 75 and one hundred fifty psi pressure courses with the 250 psi class added in 2014. The high-performance butterfly valve standard was printed in 2018 and contains 275 and 500 psi strain courses in addition to pushing the fluid circulate velocities above class B (16 feet per second) to class C (24 ft per second) and sophistication D (35 ft per second).
The first AWWA quarter-turn ball valve commonplace, C507, for 6-in. by way of 48-in. ball valves in one hundred fifty, 250 and 300 psi pressure courses was published 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) 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 first a AWWA quarter-turn valve commonplace, C517, was not revealed till 2005. The 2005 size range was three in. through seventy two in. with a 175
Example butterfly valve differential strain (top) and move fee management home windows (bottom)
strain class for 3-in. by way of 12-in. sizes and a hundred and fifty psi for the 14-in. through 72-in. The later editions (2009 and 2016) have not increased the valve sizes or pressure courses. The addition of the A velocity designation (8 fps) was added within the 2017 edition. 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 by way of 1,500 mm), C522, is beneath improvement. This standard will encompass the identical 150, 250 and 300 psi stress classes and the same fluid velocity designation of “D” (maximum 35 toes per second) as the current C507 ball valve standard.
In common, all the valve sizes, move rates and pressures have elevated because the AWWA standard’s inception.
AWWA Manual M49 identifies 10 elements that affect working torque for quarter-turn valves. These elements fall into two basic classes: (1) passive or friction-based components, and (2) active or dynamically generated components. Because valve producers cannot know the actual piping system parameters when publishing torque values, revealed torques are usually limited to the five parts of passive or friction-based parts. These embody:
Passive torque elements:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The other five elements are impacted by system parameters such as valve orientation, media and circulate velocity. The parts that make up energetic torque include:
Active torque components:
Disc weight and center of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When contemplating all these varied lively torque parts, it’s possible for the actual operating torque to exceed the valve manufacturer’s printed torque values.
Although quarter-turn valves have been used in the waterworks industry for a century, they’re being uncovered to higher service pressure and circulate price service conditions. Since the quarter-turn valve’s closure member is all the time situated in the flowing fluid, these higher service situations directly influence the valve. Operation of those valves require an actuator to rotate and/or hold the closure member within the valve’s physique as it reacts to all the fluid pressures and fluid move dynamic situations.
In addition to the elevated service circumstances, the valve sizes are also rising. The dynamic conditions of the flowing fluid have greater effect on the bigger valve sizes. Therefore, the fluid dynamic effects turn into more important than static differential strain and friction hundreds. Valves could be leak and hydrostatically shell tested during fabrication. However, the full fluid flow situations can’t be replicated earlier than website installation.
Because of the development for elevated valve sizes and increased working situations, it’s increasingly essential for the system designer, operator and owner of quarter-turn valves to raised understand the impression of system and fluid dynamics have on valve choice, development 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 strain, circulate situations, throttling, cavitation and system installation variations that instantly affect the operation and profitable use of quarter-turn valves in waterworks techniques.
The fourth edition of M49 is being developed to include the adjustments in the quarter-turn valve product requirements and installed system interactions. A new chapter shall be dedicated to methods of control 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 offer the consumer a radical image of valve efficiency over a variety of anticipated system working conditions.
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 worked at Val-Matic as Director of Engineering. He has participated in standards creating organizations, together with AWWA, MSS, ASSE and API. Dalton holds BS and MS degrees in Civil and Environmental Engineering along 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 additionally labored with the Electric Power Research Institute (EPRI) in the improvement of their quarter-turn valve efficiency prediction strategies for the nuclear energy trade.