Valve producers publish torques for his or her merchandise so that actuation and mounting hardware could be properly selected. However, revealed torque values often characterize only the seating or unseating torque for a valve at its rated pressure. While these are important values for reference, printed valve torques do not account for precise set up and operating characteristics. In order to determine the actual working torque for valves, it’s needed to understand the parameters of the piping techniques into which they are installed. Factors similar to set up orientation, path of move and fluid velocity of the media all influence 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 info on calculating operating torques for quarter-turn valves. This information appears 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 currently in its third version. In addition to info on butterfly valves, the current version additionally consists of working torque calculations for different quarter-turn valves together with plug valves and ball valves. Overall, this guide identifies 10 components of torque that can contribute to a quarter-turn valve’s operating torque.
Example torque calculation summary graph
The first AWWA quarter-turn valve commonplace for 3-in. by way of 72-in. butterfly valves, C504, was published in 1958 with 25, 50 and 125 psi pressure classes. In 1966 the 50 and one hundred twenty five psi stress courses were elevated to seventy five and a hundred and fifty psi. The 250 psi strain class was added in 2000. The 78-in. and larger butterfly valve commonplace, C516, was first revealed in 2010 with 25, 50, 75 and a hundred and fifty psi strain classes with the 250 psi class added in 2014. The high-performance butterfly valve standard was revealed in 2018 and includes 275 and 500 psi stress courses in addition to pushing the fluid flow velocities above class B (16 toes per second) to class C (24 feet per second) and sophistication D (35 feet per second).
The first AWWA quarter-turn ball valve commonplace, C507, for 6-in. via 48-in. ball valves in one hundred fifty, 250 and 300 psi pressure courses was published in 1973. In 2011, measurement vary was elevated to 6-in. through 60-in. These valves have all the time 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 commonplace for resilient-seated cast-iron eccentric plug valves in 1991, the first a AWWA quarter-turn valve standard, C517, was not revealed until 2005. The 2005 dimension vary was 3 in. via 72 in. with a one hundred seventy five
Example butterfly valve differential stress (top) and flow price management home windows (bottom)
stress class for 3-in. via 12-in. sizes and 150 psi for the 14-in. by way of 72-in. The later editions (2009 and 2016) haven’t increased the valve sizes or stress lessons. The addition of the A velocity designation (8 fps) was added within the 2017 version. This valve is primarily used in wastewater service where pressures and fluid velocities are maintained at lower 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 through 1,500 mm), C522, is underneath improvement. This commonplace will embody the same 150, 250 and 300 psi stress lessons and the identical fluid velocity designation of “D” (maximum 35 ft per second) as the present C507 ball valve standard.
In เกจวัดแรงดันอาร์กอน , all of the valve sizes, circulate rates and pressures have elevated because the AWWA standard’s inception.
AWWA Manual M49 identifies 10 elements that have an result on working torque for quarter-turn valves. These elements fall into two basic categories: (1) passive or friction-based components, and (2) active or dynamically generated elements. Because valve producers can’t know the actual piping system parameters when publishing torque values, published torques are typically restricted to the 5 parts of passive or friction-based parts. These embrace:
Passive torque elements:
Seating friction torque
Packing friction torque
Hub seal friction torque
Bearing friction torque
Thrust bearing friction torque
The different five elements are impacted by system parameters corresponding to valve orientation, media and flow velocity. The elements that make up energetic torque embody:
Active torque parts:
Disc weight and middle of gravity torque
Disc buoyancy torque
Eccentricity torque
Fluid dynamic torque
Hydrostatic unbalance torque
When contemplating all these varied lively torque elements, it is potential for the precise operating torque to exceed the valve manufacturer’s published torque values.
Although quarter-turn valves have been used within the waterworks business for a century, they are being exposed to greater service stress and flow rate service conditions. Since the quarter-turn valve’s closure member is all the time located in the flowing fluid, these higher service conditions immediately impression the valve. Operation of those valves require an actuator to rotate and/or maintain the closure member throughout the valve’s body because it reacts to all the fluid pressures and fluid circulate dynamic circumstances.
In addition to the increased service conditions, the valve sizes are additionally increasing. The dynamic circumstances of the flowing fluid have greater impact on the bigger valve sizes. Therefore, the fluid dynamic results turn out to be extra necessary than static differential strain and friction loads. Valves may be leak and hydrostatically shell tested during fabrication. However, the complete fluid move circumstances cannot be replicated earlier than website installation.
Because of the pattern for increased valve sizes and elevated operating conditions, it’s increasingly necessary for the system designer, operator and owner of quarter-turn valves to better understand the impact of system and fluid dynamics have on valve selection, development 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 conditions, throttling, cavitation and system set up differences that directly affect the operation and profitable use of quarter-turn valves in waterworks methods.
The fourth version 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 management valve sizing for fluid circulate, stress control and throttling in waterworks service. This methodology consists of explanations on using strain, move fee and cavitation graphical home windows to supply the person a thorough image of valve efficiency over a variety of anticipated system working situations.
Read: New Technologies Solve Severe Cavitation Problems
About the Authors
Steve Dalton started his profession as a consulting engineer in 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 labored at Val-Matic as Director of Engineering. He has participated in requirements growing organizations, including AWWA, MSS, ASSE and API. Dalton holds BS and MS levels 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 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 labored with the Electric Power Research Institute (EPRI) in the growth of their quarter-turn valve efficiency prediction strategies for the nuclear power trade.