Pneumatic Scotch Yoke Actuators

Pneumatic Scotch Yoke Actuators

Bettis Pneumatic Scotch Yoke Actuators offer safe and reliable torque to automate valves for a wide range of critical applications. 

The Bettis Difference

The Bettis Difference

Project overruns and maintenance costs can be draining on your operation. Bettis Scotch Yoke Modular Actuators are designed to: Provide efficiency and safety.

Keep projects on track with the immediate availability of interchangeable modules.

Deliver better cost of ownership with reduced corrosion and an industry-leading 5 Year warranty.

Lower capital cost with more efficient utilization of space in project design. Improve occupational safety during operation and service, no risk of accidental spring launch. 

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What is a Scotch Yoke Actuator?

HOW IT WORKS

Scotch yoke actuators are mechanical devices used to automatically open and close valves or dampers.

The scotch yoke is a mechanism that converts linear motion of a bar sliding back and forth into a rotational motion. 

The sliding bar is directly coupled to a piston and to a yoke with a slot that engages a sliding block.

When a force is applied to the piston, the sliding block moves in the yoke slot, causing the yoke to rotate. 

Common Scotch Yoke Applications

Scotch Yoke actuators are for automation and operation of quarter-turn valves like Butterfly, Ball and Plug valves as used in various industries like refining, pipeline, offshore, chemical, pharmaceutical, water processing, etc.

The actuators are available in two constructions: Spring Return and Double Acting. Mechanical Spring Return is for fail-safe applications and can be assembled for “Fail-Close” or “Fail-Open” safety function.

Scotch Yoke actuators are available for a wide range of advanced applications. Most well know are the temperature related trim kits that allow High Temperature or Low Temperature operation. Other applications are related special operating media, or fast operating speeds. For many of these advanced applications, dedicated control accessories are available

Torque Advantages

Scotch yoke actuators are characterized by high torque at the beginning and end of each operation. this increases safety, especially in applications where a valve remains stationary for long periods of time. When compared to rack and pinion, a scotch yoke using the same cylinder bore and equal air supply pressure develops a higher torque.

The yoke can either be symmetric or canted, symmetric produces high torque at the beginning and end of the stroke, while canted produces higher break open torque. Using a canted yoke can reduce actuator size, weight, and cost when valve has appropriate torque requirements.

Typical Scotch Yoke Controls

Utilizing vast experience in the industry, Emerson's expert engineers designed a modular control system that eliminates the need to source components from individual suppliers and manage documentation. The Emerson Bettis™ VOS-PAC is a turnkey valve operating system (VOS) package with an actuator and fully integrated controls that allows large scale fixed installations to access faster commissioning, with the assurance of quality.

The integrated pneumatic actuation package includes air filter regulators, relief valves, solenoid valves, limit switches, positioners, as well as the piping and engineering as a single solution.

Origin

The term scotch yoke comes from two words which were used together in a specific way.

Scotch - a chock to prevent rolling or slipping. noun used in 1639, in this meaning.

Yoke- a clamp or similar piece that embraces two parts to hold or unite them in position, used around 900.

Scotch yoke : a slotted crosshead used (as in a donkey engine or steam fire engine) in place of a connecting rod, first used around 1911 as the two words put together.

Modular Solutions

HOW IT WORKS

Change is Power Module, Drive Module and Spring Module constant and Bettis Scotch Yoke G Series actuators in the industry that can provide the flexibility needed for ever changing challenges. G Series modules can be assembled for various valve requirements with three main modules, power, drive, and spring.


Modules are installed and removed easily with a simple plug and play, bolt on approach. No special tools or exhaustive training is required. No other actuator has this level of interchangeable functionality. 

Immediate Availability

In Stock

With modular components, your specific requirements can be met with 24-hour availability of parts.

Available Experts

172 global distributors allow for access to experts in your area with the equipment you need.

Global Support

Over 1,500 authorized service technicians provides access to expertise when you need it.

Project Efficiency

The majority of projects have cost and time overruns due to change orders, often last minute. With Bettis Scotch Yoke Modular actuators, power and spring modules are easily interchangeable to allow adjustments in the field, eliminating the need for re-engineering and rebuilding of a full actuator. What could take weeks to re-engineer and build can be adjusted immediately, keeping projects on track.

Easy Maintenance

When repair or maintenance is required for an actuator in the field, the traditional method is to find the correct repair kit in the inventory and disassemble the unit in the field.

With Bettis Scotch Yoke Modular actuators in stock, a simple field swap could be accomplished very quickly by even the most un-skilled worker. After the new module is put in service, the old module can be brought back to inventory and be maintained, repaired and ready for future use. No other actuators allow the user to repair and change the equipment with this kind of inventory modularity.

Longer Cycle Life

Actuators with external tie bars can suffer from premature corrosion problems due to inadequate “paint” coverage between tie bars, bolts, and cylinder walls.

Bettis Scotch Yoke Modular actuators have no external tie bars, eliminating tie bar failure due to external factors such as corrosion or impact. G-Series actuators incorporate protective internal and external coatings, assuring the actuator’s reliable operation in the harshest of environments. Construction features allow the G-Series actuators to meet IP67M specifications and corrocsion as confirmed by Salt Spray Testing per ASTM B117 criteria

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Longer Life Cycle

Compact Solution

The Bettis G-Series Scotch Yoke Modular actuator design has the spring inward of piston for a pull motion, instead of having the spring push the piston rod.'

More efficient use of space and less weight for the Same Torque

  • 20-30% Weight Reduction
  • 20-30%% Space Savings

The inward spring design allows for the actuator’s center of gravity to be closer to the valve shaft, reducing side load and improving valve life. With the G-Series design, weight and space are reduced around 20% to comparable torque of other similar actuators. Due to the more balanced operation, cycle life can be improved up to 40%. Extending the life of equipment and improving up time

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High Efficiency

Increased Safety

Bettis Scotch Yoke Modular actuators provide the highest safety for spring return actuation.

With  it's unique design, the G-Series has no pressure on the end cap and the Tension-Lok (TM) prevents spring launch.

Tension-Lok positively locks the spring module in place while under load and in pre-compression,

avoiding the possibility of the compressed spring launching out of the spring can and causing injury.

The only way to release the spring is by following the correct disassembly procedure, after tension is relieved and the spring is decompressed.

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Tenison-Lok nut
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