The Kinetrol rotary vane design is based upon a single moving part which eliminates additional parts required to convert linear motion to rotary motion. This simple and innovative design provides a highly accurate and extremely reliable actuator for operating valves, drives and dampers, and is perfectly suited for the most demanding process control applications. For more information visit www.kinetrolusa.com or call 972-447-9443.
Kinetrol is pleased to announce the introduction of the new Model 60 Actuator which will now increase the torque capability of the Kinetrol range to 356,977 inch pounds.
An Upper Midwest water treatment plant was experiencing high failure rates, long maintenance periods, and too many repair issues with their existing pneumatic scotch-yoke cylinder valve operators.
Upon investigation, the problem boiled down to how the scotch-yoke cylinder's linear movement is converted to rotational movement. To do so requires gearing, yokes and linkage which are wear points. In medium to high cycle rate applications these wear points soon become failure points.
Kinetrol rotary vane actuators utilize a single moving part - the one-piece vane and shaft. There are no gears, yokes, or linkages and 100% of the movement is transferred to the actuator shaft. The one piece vane and shaft eliminates these wear points, and therefore eliminates the resulting failure points.
Out with the old.
In with the new.
After a planning review meeting, this particular water treatment plant clearly saw the advantages of the Kinetrol design. The argument was so strong and the case so clear, they decided to replace all (60) scotch-yoke cylinder actuated valves with Kinetrol vane actuators in one fell swoop.
The new actuators have been operating for 6 months now without problem, cycling approximately 15 times per day.
Click on the images above to see a larger view. For more information, contact Kinetrol USA by visiting https://kinetrolusa.com or by calling 972-447-9443
Industrial valves, dampers and louvers are operated either electrically or pneumatically. This post compares the three major categories of pneumatic valve actuators, namely:
All three categories provide the same basic function - converting air pressure to rotational movement intended to open, close, or position a quarter-turn valve (ball, plug, butterfly), louver or damper.
All three can be configured in either direct acting or spring return versions. Direct acting actuators use the air supply to move the actuator in both directions (open and close). Spring return actuators, as the name implies, uses springs to move the actuator back to its "resting" state. Converting from direct acting to spring return is done through simple modifications, typically just adding an external spring module, or removing the end caps from rack and pinion actuators and installing several coil springs.
Rotary Vane Actuator
Rotary Vane Actuators
Vane actuators generally provide the most space savings when comparing size-to-torque with rack and pinion and scotch yoke. They have an outstanding reputation for long life because then contain only one moving part, as opposed to rack and pinion and scotch yoke actuators that have many. They tend to withstand dirty and corrosive atmospheres better than rack and pinion and scotch yoke actuators. Vane actuators also use externally mounted, helically wound "clock springs" for their spring return mechanism.
Scotch Yoke
Scotch-yoke actuators use a pneumatic piston mechanism to transfer movement to a linear push rod, that in turn engages a pivoting lever arm to provide rotation. They come in a wide variety of sizes, but are very often used on larger valves because they are capable of producing very high torque output. Spring return units have a large return spring module mounted on the opposite end of the piston mechanism working directly against the pressurized cylinder.
Rack and Pinion
A rack & pinion pneumatic actuator uses opposing pistons with integral gears to engage a pinion gear shaft to produce rotation. Rack & pinion actuators (sometimes referred to as a lunch box because of their shape) tend to be more compact than scotch yoke, have standardized mounting patterns, and produce output torques suitable for small to medium sized valves. They almost always include standard bolting and coupling patterns to directly attach a valve, solenoid, limit switch or positioner. Rack and pinion actuators use several smaller coil springs mounted internally and provide the torque to return the valve to its starting position.
The practical difference between these three types of pneumatic actuators comes down to size, power, torque curve and ease of adding peripherals. For the best selection of valve actuator for any quarter turn valve application, you should seek the advice of a qualified valve automation specialist. By doing so your valve actuation package will be optimized for safety, longevity, and performance.
Scotch yoke mechanism image courtesy of Wikipedia. Rack and pinion mechanism image courtesy of Wikipedia.
Kinetrol vane actuators perform in the toughest applications.
Due to the use of gears, slides, pins, and yokes, rack & pinion and scotch-yoke design actuators are less reliable than Kinetrol vane actuators.
Kinetrol's design is based upon a single moving part, which eliminates additional parts required to convert linear motion to rotary motion. This simple and innovative design provides a highly accurate and extremely reliable actuator for operating valves, drives and dampers, and is perfectly suited for the most demanding process control control applications.
For more information, visit http://www.kinetrolusa.com
According to Wikipedia, elegance is "a synonym for beauty that has come to acquire the additional connotations of unusual effectiveness and simplicity." In engineering terms, "a solution may be considered elegant if it uses a non-obvious method to produce a solution which is highly effective and simple. "
When you compare the mechanics of various other pneumatic valve actuators, such as rack and pinion or scotch yoke with their internal gears, bushings and bearings, you immediately understand that simplicity is sacrificed and the design is certainly not elegant.
Actuators with gears wear.
When gears mesh, there is friction. Friction causes heat and wear, which effects the mechanical life of the actuator. Friction converts kinetic energy into thermal energy and can have dramatic consequences if left unchecked. Another important consequence of friction is wear, which may lead to performance degradation and/or damage to the internal components of a rack and pinion or scotch yoke actuator.
"Fretting wear" is caused by the repeated cyclical rubbing between two surfaces (gears in the case of scotch yoke or rack and pinion actuators) and over a period of time, will remove material from one or both surfaces.
Backlash happens when gears change direction. It is caused by the gap between the trailing face of the driving tooth and the leading face of the tooth behind it. The gap must be closed before force can be transferred in the new direction, hence the phenomena of backlash. This is also sometimes referred to as "slop".
A well designed vane actuator uses a single piece of machined steel for both the vane body and drive shafts. With this design, the shaft and vane are not affected by backlash, friction or wear.
For more information, contact:
Kinetrol USA
1085 Ohio Drive
Plano, Texas 75093
(972) 447-9443 phone
(972) 447-9720 fax sales@kinetrolusa.com
When it comes to pneumatically actuating an industrial quarter-turn valve, you basically have only three types of mechanical technologies to choose from: rack and pinion, scotch yoke and the rotary vane design. This post describes why a rotary vane design is the clear winner when it comes to efficiency and reliability.
First, let's describe how rack and pinion and scotch yoke actuators work.
A rack and pinion actuator is comprised of two opposing pistons, each with its own gear (referred to as the "rack"). The two piston racks are set against a round pinion gear. As pressure increases against one side of each piston, each rack moves linearly against the opposite sides of the pinion gear causing rotational movement. This rotational movement is used to open and close a valve. Pretty basic stuff. See the animation (provided by Wikipedia) below for a visual understanding.
Note rack and pinion gears
and how they are prone to
wear and slop.
A scotch yoke actuator relies on the scotch yoke mechanism to convert linear movement into rotary motion. In this case, a piston is coupled to the sliding yoke, which in turn moves a fixed pin on the shaft of the actuator to provide rotation. As one side of the piston is pressurized, the piston forces the yoke to move linearly, which allows a slot in the yoke to drive the pin on the actuator shaft. See the animation (from Wikipedia) below for clarification:
Scotch yoke operation. Easy to see its highly
susceptible to wear and resulting slop.
Both of these valve actuator mechanisms use several interconnected, mechanical moving parts. As a result, they are very susceptible to wear.
It All Comes Down to "A Single Moving Part"
The vane actuator has only one moving part and there is no linear-to-rotary conversion. An internal vane moves uniformly in response to inlet air pressure, without gears, slots, or levers. This is a clear advantage when you consider wear and tear, and also machine efficiency. See the video below for a visual explanation.
One moving part --------------------------- Many moving parts
No O-rings ---------------------------------- Several sets of O-rings
Dynamic Memory Seals ------------------ Static seals
No linear to rotary motion ---------------- Linear to rotary = friction/wear
Spring isolated ------------------------------ Spring exposed to atmosphere
Very accurate control ---------------------- Hysteresis = poor control
Non-pressurized shafts -------------------- Pressurized shafts
4 million operations ------------------------ 500,000 to 1 million operations
Kinetrol is pleased to announce the introduction of the new Model 60 Actuator which will now increase the torque capability of the Kinetrol range to 356,977 inch pounds.
