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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, printed torque values typically symbolize only 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 precise set up and working traits. In order to find out the actual working torque for valves, it is essential to grasp the parameters of the piping methods into which they are put in. Factors such as installation orientation, course of move and fluid velocity of the media all influence the actual 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 data on calculating operating torques for quarter-turn valves. This data 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 at present in its third edition. In addition to information on butterfly valves, the present edition also includes working torque calculations for different quarter-turn valves together with plug valves and ball valves. Overall, this handbook identifies 10 components of torque that may 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. through 72-in. butterfly valves, C504, was revealed in 1958 with 25, 50 and one hundred twenty five psi strain classes. In 1966 the 50 and one hundred twenty five psi pressure courses have been increased to seventy five and a hundred and fifty psi. The 250 psi stress class was added in 2000. The 78-in. and larger butterfly valve standard, C516, was first printed in 2010 with 25, 50, 75 and one hundred fifty psi stress courses 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 stress courses as nicely as pushing the fluid circulate velocities above class B (16 feet per second) to class C (24 toes per second) and class D (35 ft per second).
The first AWWA quarter-turn ball valve standard, C507, for 6-in. through 48-in. ball valves in one hundred fifty, 250 and 300 psi pressure courses was revealed in 1973. In 2011, measurement range was elevated to 6-in. through 60-in. These valves have always 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 standard, C517, was not revealed till 2005. The 2005 dimension range was 3 in. through seventy two in. with a 175

Example butterfly valve differential pressure (top) and move rate control windows (bottom)

pressure class for 3-in. by way of 12-in. sizes and one hundred fifty psi for the 14-in. through 72-in. digital pressure gauge (2009 and 2016) haven’t increased the valve sizes or strain courses. The addition of the A velocity designation (8 fps) was added within the 2017 edition. This valve is primarily utilized 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 same 150, 250 and 300 psi strain classes and the same fluid velocity designation of “D” (maximum 35 toes per second) as the present C507 ball valve commonplace.
In basic, all of the valve sizes, circulate charges and pressures have elevated for the explanation that AWWA standard’s inception.
COMPONENTS OF OPERATING TORQUE

AWWA Manual M49 identifies 10 parts that have an result on operating torque for quarter-turn valves. These elements fall into two basic categories: (1) passive or friction-based parts, and (2) lively or dynamically generated components. Because valve producers cannot know the actual piping system parameters when publishing torque values, printed torques are usually limited to the five elements of passive or friction-based parts. 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 elements are impacted by system parameters similar to valve orientation, media and flow velocity. The parts that make up active torque embody:
Active torque parts:
Disc weight and center of gravity torque

Disc buoyancy torque

Eccentricity torque

Fluid dynamic torque

Hydrostatic unbalance torque

When considering all these varied energetic torque elements, it is potential for the actual operating torque to exceed the valve manufacturer’s revealed torque values.
WHY IS M49 MORE IMPORTANT TODAY?

Although quarter-turn valves have been used in the waterworks business for a century, they are being exposed to larger service strain and circulate rate service circumstances. Since the quarter-turn valve’s closure member is always positioned in the flowing fluid, these greater service circumstances instantly impression the valve. Operation of these valves require an actuator to rotate and/or hold the closure member within the valve’s body because it reacts to all of the fluid pressures and fluid flow dynamic conditions.
In addition to the increased service situations, the valve sizes are also rising. The dynamic circumstances of the flowing fluid have larger impact on the larger valve sizes. Therefore, the fluid dynamic effects become extra important than static differential strain and friction masses. Valves could be leak and hydrostatically shell examined throughout fabrication. However, the full fluid flow situations cannot be replicated earlier than website set up.
Because of the trend for increased valve sizes and increased operating situations, it’s increasingly important for the system designer, operator and owner of quarter-turn valves to higher perceive the impression of system and fluid dynamics have on valve choice, construction and use.
The AWWA Manual of Standard Practice M 49 is dedicated to the understanding of quarter-turn valves together with working torque necessities, differential strain, move circumstances, throttling, cavitation and system set up differences that immediately influence 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 installed system interactions. A new chapter might be dedicated to methods of control valve sizing for fluid move, pressure control and throttling in waterworks service. This methodology includes explanations on the use of strain, circulate fee and cavitation graphical home windows to supply the person a thorough picture of valve performance over a spread of anticipated system operating situations.
Read: New Technologies Solve Severe Cavitation Problems

About the Authors

Steve Dalton began 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 beforehand labored at Val-Matic as Director of Engineering. He has participated in standards creating organizations, including 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 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 development of their quarter-turn valve efficiency prediction methods for the nuclear power trade.
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