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.
Besides pneumatic valve actuation, Kinetrol vane actuators are used widely on controlling industrial and commercial louvers and dampers.
The video below gives you a short visual demo of a louver being opened, closed and positioned with a Kinetrol vane actuator and electro-pneumatic positioner.
Louvers and dampers are used to stop or regulate the flow of air inside a duct, chimney, air handler, or other air handling equipment.
Offshore oil rigs present some special challenges to pneumatic actuator manufacturers. First, the corrosive marine environment takes a harsh toll on the internal and external parts of a typical actuator. Rack and pinion actuators are particularly susceptible.
Because rotary vane actuators, (such as Kinetrol) or their spring units, don't "breathe" ambient air, they have great immunity to internal corrosion. Also, a very durable, epoxy enamel finish and stainless steel hardware provide maximum external protection.
Ideal for corrosive, marine installation.
Another challenge for offshore use is the very limited space available. Facilitation of large scotch yoke actuators, is quite difficult. Actuators such as Kinetrol's compact vane design with integral direct-mount limit switch make it a perfect choice in applications where space is at a premium. In these cramped and below grating installations you want the long maintenance-free life that you can install with confidence for years of service.
Click on images for larger view.
Low maintenance is important
in hard to get to places
Here is an easy-access, online vane actuator catalog from Kinetrol that includes pneumatic actuators, spring return units, positioners, indicators, limit switches, solenoid valves, and other valve actuation equipment.
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
The following video demonstrates the Kinetrol Model 20, double acting, pneumatic vane actuator as it closes a large butterfly valve.
The Model 20 actuator is capable of delivering 89,000 inch pounds of torque at 80 PSI. The unit you see below is equipped with a dual coil, 4-way solenoid valve to control air flow to either side of the actuator, as well as control the opening / closing time. The actuator below also is equipped with a Kinetrol Universal Limit Switch with visual indication and internal electrical contacts.
The EL positioner controls airflow to an actuator and moves it to a position determined by a 4-20mA signal and using a unique low power proportional servo valve.
The microprocessor in the loop-powered 4- 20mA position circuit reads the signal via one channel of a 12-bit A-D converter, reads the position voltage from the feedback potentiometer via the second channel of the
A-D converter, and compares the two. If it detects a position which is different from that required by the signal, it changes the output to the servo valve, in order to drive the actuator in the direction required to reach the correct position. As the actuator moves, the feedback potentiometer voltage changes and the microprocessor continually calculates the adjustments required for the servo valve in order to guide the actuator accurately into position. The microprocessor is programmed with a sophisticated but compact algorithm which allows this critical dynamic valve adjustment to be made correctly. This in turn gives optimal results with any actuator/load combination - slow or fast, low or high friction, low or high inertia. All can be optimized by tuning the PGAIN and DAMP push buttons via the positioner circuit push buttons.
