Understanding Torque for Quarter-Turn Valves

Valve producers publish torques for his or her merchandise so that actuation and mounting hardware can be correctly chosen. However, published torque values typically symbolize solely the seating or unseating torque for a valve at its rated strain. While these are important values for reference, revealed valve torques don’t account for actual installation and working traits. In order to determine the actual operating torque for valves, it is needed to know the parameters of the piping systems into which they’re installed. Factors corresponding to set up orientation, path of circulate and fluid velocity of the media all impact the precise working torque of valves.
Trunnion mounted ball valve operated by a single appearing spring return actuator. Photo credit: Val-Matic

The American Water Works Association (AWWA) publishes detailed information on calculating working 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 version. In addition to data on butterfly valves, the current edition also consists of working torque calculations for other quarter-turn valves together with plug valves and ball valves. Overall, this guide identifies 10 components of torque that may contribute to a quarter-turn valve’s operating torque.
Example torque calculation abstract graph


The first AWWA quarter-turn valve commonplace for 3-in. via 72-in. butterfly valves, C504, was printed in 1958 with 25, 50 and one hundred twenty five psi stress courses. In 1966 the 50 and one hundred twenty five psi strain courses had been elevated to 75 and one hundred fifty psi. The 250 psi stress class was added in 2000. The 78-in. and larger butterfly valve normal, C516, was first printed 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 normal was revealed in 2018 and contains 275 and 500 psi strain classes as nicely as pushing the fluid move velocities above class B (16 ft per second) to class C (24 feet per second) and sophistication D (35 toes 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 strain courses was printed in 1973. In 2011, dimension range was elevated to 6-in. via 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 normal for resilient-seated cast-iron eccentric plug valves in 1991, the primary a AWWA quarter-turn valve normal, C517, was not revealed until 2005. The 2005 measurement vary was three in. via 72 in. with a 175

Example butterfly valve differential strain (top) and move rate management home windows (bottom)

pressure class for 3-in. through 12-in. sizes and 150 psi for the 14-in. via 72-in. The later editions (2009 and 2016) haven’t increased the valve sizes or strain classes. The addition of the A velocity designation (8 fps) was added in the 2017 version. This valve is primarily used in wastewater service where pressures and fluid velocities are maintained at lower values.
The need 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 commonplace 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 commonplace.
In general, all of the valve sizes, circulate rates and pressures have increased since the AWWA standard’s inception.

AWWA Manual M49 identifies 10 parts that affect operating torque for quarter-turn valves. These parts fall into two basic classes: (1) passive or friction-based elements, and (2) energetic or dynamically generated parts. Because valve manufacturers cannot know the actual piping system parameters when publishing torque values, published torques are usually limited to the five parts of passive or friction-based components. These embody:
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 move velocity. The elements that make up lively torque include:
Active torque elements:
Disc weight and center of gravity torque

Disc buoyancy torque

Eccentricity torque

Fluid dynamic torque

Hydrostatic unbalance torque

When considering all these numerous energetic torque elements, it’s potential for the precise working torque to exceed the valve manufacturer’s revealed torque values.

Although quarter-turn valves have been used within the waterworks industry for a century, they are being uncovered to greater service pressure and flow rate service circumstances. Since the quarter-turn valve’s closure member is at all times situated within the flowing fluid, these greater service conditions instantly impression the valve. Operation of these valves require an actuator to rotate and/or maintain the closure member inside the valve’s physique as it reacts to all the fluid pressures and fluid move dynamic circumstances.
In addition to the increased service circumstances, the valve sizes are additionally growing. The dynamic circumstances of the flowing fluid have greater impact on the larger valve sizes. Therefore, the fluid dynamic effects become more necessary than static differential pressure and friction loads. Valves could be leak and hydrostatically shell tested throughout fabrication. However, the total fluid circulate circumstances can’t be replicated before site installation.
Because of the trend for elevated valve sizes and increased operating conditions, it’s more and more important for the system designer, operator and owner of quarter-turn valves to raised understand the influence of system and fluid dynamics have on valve choice, building and use.
The AWWA Manual of Standard Practice M forty nine is dedicated to the understanding of quarter-turn valves including working torque necessities, differential pressure, circulate situations, throttling, cavitation and system installation variations that immediately affect the operation and profitable use of quarter-turn valves in waterworks methods.

The fourth version of M49 is being developed to include the modifications within the quarter-turn valve product requirements and put in system interactions. A new chapter might be dedicated to strategies of control valve sizing for fluid move, strain management and throttling in waterworks service. This methodology contains explanations on using strain, move rate and cavitation graphical home windows to provide the user an intensive image of valve performance over a variety of anticipated system operating conditions.
Read: New Technologies Solve Severe Cavitation Problems

About the Authors

Steve Dalton started his career as a consulting engineer within 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 beforehand worked at Val-Matic as Director of Engineering. He has participated in standards creating organizations, together with AWWA, MSS, ASSE and API. pressure gauge วัด แรง ดัน น้ำ 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.” 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 energy business.

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