Exploring the Superior Features of Vane Actuators in Contrast to Rack & Pinion and Scotch-Yoke Designs

Pneumatic actuators are vital components in many industrial processes, enabling the automation of valve and damper operations. The three most commonly used types of pneumatic actuators are vane, rack and pinion, and scotch yoke. This post provides an analysis of the technical design differences between these actuators, focusing on the advantages of Kinetrol vane actuators. We will also discuss why Kinetrol vane actuators last longer in industrial valve and damper applications, and how they provide a lower cost of ownership than other types of pneumatic actuators.

Design Differences Between Vane Actuators, Rack and Pinion Actuators, and Scotch Yoke Actuators

Kinetrol Pneumatic Vane Actuators

Kinetrol pneumatic vane actuators utilize a simple yet effective design consisting of a central shaft connected to a flat vane inside a semi-cylindrical housing. When pressurized air is applied to the housing, the vane rotates the central shaft, creating a rotary motion that operates the valve or damper.

Pneumatic Rack and Pinion Actuators

Pneumatic rack and pinion actuators consist of a piston connected to a rack, which engages with a pinion gear on the output shaft. As the piston moves linearly, the rack converts this motion into rotation through the pinion gear, driving the output shaft.

Scotch Yoke Actuators

Scotch yoke actuators employ a slotted yoke mechanism that translates linear motion from a piston into rotary motion. The piston rod has a pin that engages with the yoke, which in turn is connected to the output shaft. As the piston moves, the pin slides within the yoke slot, causing the yoke to rotate the output shaft.

Advantages of Kinetrol Pneumatic Vane Actuators

Simplicity and Compactness

Kinetrol vane actuators boast a simple design with fewer moving parts compared to rack and pinion or scotch yoke actuators. This simplicity results in a more compact and lightweight unit, which requires less space and is easier to install and maintain.

High Torque-to-Size Ratio

Kinetrol vane actuators have an exceptional torque-to-size ratio, providing more torque per unit size compared to other actuators. This enables Kinetrol actuators to deliver powerful performance even in space-constrained applications.

Less Friction and Wear

The design of Kinetrol vane actuators minimizes contact between moving parts, resulting in reduced friction and wear. This leads to a longer service life and lower maintenance requirements.

Smooth, Precise Control

Kinetrol actuators provide smooth and precise control of the valve or damper position, with minimal backlash or hysteresis. This ensures accurate and consistent process control, essential for maintaining product quality and efficient operations.

Longer Life in Industrial Valve and Damper Applications and Lower Cost of Ownership

Kinetrol vane actuators last significantly longer in industrial valve and damper applications due to their design, which minimizes friction and wear. Their simple construction and fewer moving parts result in reduced likelihood of component failure and increased resistance to harsh operating conditions. This translates into fewer breakdowns, less downtime, and lower maintenance costs.

The cost advantages of Kinetrol pneumatic vane actuators stem from their durability, ease of maintenance, and lower energy consumption. With fewer components to replace, lower maintenance requirements, and longer service.

For more information, contact:
Kinetrol USA
https://kinetrolusa.com
972-447-9443

New Product: Kinetrol Model 60 Rotary Vane Actuator

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.

Kinetrol Model 60 Feature and Options

• Double-Acting and Spring-Return options
• 2” Air ports as standard
• Standard working temperature range: -40°F
• to +176°F
• Angle of travel adjustable 80 to 100 degrees
• Displaced volume: 6284 in³
• Weight (less coupling): 998.7 pounds
• Coupling weight: 48.5 pounds
• VLS / ULS / XLS Limit Switch Box options
• AP Positioner options
• ATEX Category 2 approved

Kinetrol Model 60 Materials of Construction

• Casing: Sand cast aluminum alloy
• Vane & Output shaft: SG Iron, zinc plated
• Shaft bushes: PTFE coated bronze
• Seals: Molded polyurethane
• Seal expenders: Stainless spring steel
• Coupling: Weldable mild steel, zinc plated

For more information, contact Kinetrol USA by calling 972-447-9443 or visit their web site at https://kinetrolusa.com.

Upper Midwest Water Treatment Plant says "Out with the old, in with the new!"

Before project.

Project begins.

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

Pneumatic Valve and Damper Actuators: A Design Comparison

Industrial valves, dampers and louvers are operated either electrically or pneumatically. This post compares the three major categories of  pneumatic valve actuators, namely:

1. Rotary vane
2. Scotch-yoke
3. Rack & pinion

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.

Why Vane Actuators Outlast and Outperform Rack & Pinion and Scotch Yoke Designs

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

Elegantly Engineered Pneumatic Valve Actuators. A Simple, Single Moving Part

One moving part. Simple. Elegant.

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

Why the Rotary Vane Actuator Design is Superior to Rack and Pinion & Scotch Yoke Designs

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.

Vane = Simple, reliable design --------- Piston = Complicated, less reliable

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