Valve manufacturers publish torques for their merchandise so that actuation and mounting hardware may be correctly chosen. However, printed torque values typically characterize solely the seating or unseating torque for a valve at its rated pressure. While these are necessary values for reference, published valve torques do not account for actual installation and operating traits. In order to determine the precise operating torque for valves, it’s essential to grasp the parameters of the piping systems into which they are installed. Factors similar to set up orientation, course of move and fluid velocity of the media all impact the precise working torque of valves.
Trunnion mounted ball valve operated by a single acting spring return actuator. Photo credit score: Val-Matic
The American Water Works Association (AWWA) publishes detailed info on calculating operating torques for quarter-turn valves. This information 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 presently in its third edition. In addition to information on butterfly valves, the present edition also contains working torque calculations for other quarter-turn valves together with plug valves and ball valves. Overall, this guide identifies 10 elements of torque that can contribute to a quarter-turn valve’s operating torque.
Example torque calculation abstract graph
The first AWWA quarter-turn valve standard for 3-in. via 72-in. butterfly valves, C504, was published in 1958 with 25, 50 and a hundred twenty five psi strain classes. In 1966 the 50 and a hundred twenty five psi strain lessons were increased to seventy five and one hundred fifty psi. The 250 psi pressure class was added in 2000. The 78-in. and larger butterfly valve normal, C516, was first printed in 2010 with 25, 50, seventy five and 150 psi strain courses with the 250 psi class added in 2014. The high-performance butterfly valve commonplace was printed in 2018 and contains 275 and 500 psi pressure lessons as well as pushing the fluid circulate velocities above class B (16 feet 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 a hundred and fifty, 250 and 300 psi pressure lessons was revealed in 1973. In 2011, size vary was increased to 6-in. by way of 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 printed till 2005. The 2005 size vary was 3 in. via 72 in. with a 175
Example butterfly valve differential pressure (top) and flow rate control windows (bottom)
stress class for 3-in. via 12-in. sizes and one hundred fifty psi for the 14-in. by way of 72-in. The later editions (2009 and 2016) haven’t increased the valve sizes or stress courses. 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 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 via 1,500 mm), C522, is beneath growth. This normal will encompass the same a hundred and fifty, 250 and 300 psi stress lessons and the same fluid velocity designation of “D” (maximum 35 ft per second) as the present C507 ball valve standard.
In common, all of the valve sizes, circulate rates and pressures have elevated because the AWWA standard’s inception.
AWWA Manual M49 identifies 10 components that affect working torque for quarter-turn valves. These elements fall into two common categories: (1) passive or friction-based elements, and (2) active or dynamically generated components. Because valve manufacturers can’t know the precise piping system parameters when publishing torque values, printed torques are typically restricted to the five parts of passive or friction-based elements. These include:
Passive torque components:
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 flow velocity. The parts that make up lively torque embody:
Active torque parts:
Disc weight and heart of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When contemplating all these varied energetic torque parts, it is attainable for the precise working torque to exceed the valve manufacturer’s published torque values.
Although quarter-turn valves have been used within the waterworks industry for a century, they are being uncovered to higher service strain and circulate rate service situations. Since the quarter-turn valve’s closure member is at all times located in the flowing fluid, these higher service conditions immediately impact 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 circulate dynamic conditions.
In addition to the elevated service conditions, the valve sizes are additionally increasing. The dynamic conditions of the flowing fluid have higher impact on the bigger valve sizes. Therefore, the fluid dynamic effects turn into extra necessary than static differential stress and friction hundreds. Valves can be leak and hydrostatically shell examined during fabrication. However, the complete fluid flow circumstances can’t be replicated before site set up.
Because of the pattern for elevated valve sizes and elevated operating circumstances, it’s more and more essential for the system designer, operator and owner of quarter-turn valves to higher perceive the influence 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 requirements, differential stress, move situations, throttling, cavitation and system installation variations that instantly affect the operation and successful use of quarter-turn valves in waterworks techniques.
The fourth version of M49 is being developed to include the adjustments in the quarter-turn valve product requirements and put in system interactions. A new chapter shall be dedicated to strategies of control valve sizing for fluid flow, strain management and throttling in waterworks service. This methodology contains explanations on using strain, flow rate and cavitation graphical home windows to offer the consumer an intensive picture of valve performance over a variety of anticipated system working situations.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton began his profession as a consulting engineer within the waterworks business in Chicago. เกจวัดแรงดันต่ำ joined Val-Matic in 2011 and was appointed president of Val-Matic in May 2021, following the retirement of John Ballun. Dalton previously worked 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 concerned in quarter-turn valve and actuator engineering and design for 50 years and has been an lively member of both 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 additionally labored with the Electric Power Research Institute (EPRI) within the growth of their quarter-turn valve performance prediction strategies for the nuclear power business.