Valve producers publish torques for their merchandise in order that actuation and mounting hardware can be correctly chosen. However, published torque values often symbolize solely the seating or unseating torque for a valve at its rated pressure. While these are essential values for reference, published valve torques don’t account for precise set up and operating characteristics. In order to determine the precise operating torque for valves, it is necessary to understand the parameters of the piping methods into which they are put in. Factors corresponding to set up orientation, direction of circulate and fluid velocity of the media all impression the precise operating torque of valves.
Trunnion mounted ball valve operated by a single performing 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 info seems in AWWA Manual M49 Quarter-Turn Valves: Head Loss, Torque, and Cavitation Analysis. Originally published in 2001 with torque calculations for butterfly valves, AWWA M49 is at present in its third version. In addition to information on butterfly valves, the present version additionally includes operating torque calculations for different quarter-turn valves including plug valves and ball valves. Overall, this guide identifies 10 elements 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 commonplace for 3-in. through 72-in. butterfly valves, C504, was printed in 1958 with 25, 50 and 125 psi stress classes. In 1966 the 50 and one hundred twenty five psi strain courses had been elevated to seventy five and a hundred and fifty psi. The 250 psi strain class was added in 2000. The 78-in. and bigger butterfly valve normal, C516, was first printed in 2010 with 25, 50, 75 and a hundred and fifty psi pressure classes with the 250 psi class added in 2014. The high-performance butterfly valve commonplace was printed in 2018 and consists of 275 and 500 psi stress lessons as properly as pushing the fluid flow velocities above class B (16 toes per second) to class C (24 ft per second) and sophistication D (35 feet per second).
The first AWWA quarter-turn ball valve commonplace, C507, for 6-in. by way of 48-in. ball valves in a hundred and fifty, 250 and 300 psi pressure courses was printed in 1973. In 2011, size vary was elevated 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 normal for resilient-seated cast-iron eccentric plug valves in 1991, the primary a AWWA quarter-turn valve commonplace, C517, was not revealed till 2005. The 2005 measurement vary was 3 in. by way of 72 in. with a 175
Example butterfly valve differential stress (top) and flow price control home windows (bottom)
strain class for 3-in. through 12-in. sizes and one hundred fifty psi for the 14-in. via 72-in. The later editions (2009 and 2016) have not 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 used in wastewater service where pressures and fluid velocities are maintained at lower 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 through 1,500 mm), C522, is underneath improvement. This normal will embody the identical 150, 250 and 300 psi stress courses and the same 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 rates and pressures have increased since the AWWA standard’s inception.
COMPONENTS OF OPERATING TORQUE
AWWA Manual M49 identifies 10 parts that affect operating torque for quarter-turn valves. These components fall into two basic classes: (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, published torques are generally limited to the five parts of passive or friction-based parts. These include:
Passive torque elements:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The other 5 elements are impacted by system parameters corresponding to valve orientation, media and circulate velocity. The elements that make up energetic torque embrace:
Active torque elements:
Disc weight and heart of gravity torque
Disc buoyancy torque
Fluid dynamic torque
Hydrostatic unbalance torque
When considering all these numerous lively torque parts, it’s attainable for the actual 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 trade for a century, they are being uncovered to larger service stress and circulate fee service situations. Since the quarter-turn valve’s closure member is all the time positioned within the flowing fluid, these greater service situations immediately impact the valve. Operation of those valves require an actuator to rotate and/or hold the closure member within the valve’s body as it reacts to all the fluid pressures and fluid flow dynamic circumstances.
In addition to the increased service situations, the valve sizes are also growing. The dynamic situations of the flowing fluid have larger effect on the bigger valve sizes. Therefore, the fluid dynamic effects turn out to be extra essential than static differential strain and friction hundreds. Valves can be leak and hydrostatically shell examined throughout fabrication. However, the full fluid flow circumstances cannot be replicated before web site installation.
Because of the pattern for increased valve sizes and elevated working circumstances, it’s increasingly essential for the system designer, operator and proprietor 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 necessities, differential stress, circulate circumstances, throttling, cavitation and system installation differences that directly influence the operation and profitable 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 include the changes in the quarter-turn valve product requirements and installed system interactions. เกจวัดแรงดันลมขนาดเล็ก will be dedicated to methods of control valve sizing for fluid move, pressure control and throttling in waterworks service. This methodology contains explanations on the use of pressure, flow fee and cavitation graphical windows to offer the consumer an intensive image of valve performance over a spread of anticipated system working situations.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton began his profession 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 previously labored at Val-Matic as Director of Engineering. He has participated in standards growing 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 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 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) in the development of their quarter-turn valve performance prediction methods for the nuclear energy industry.
fittingthai.com & radiusglobal.co.th Shop power by Odoo ERP