Bettis CBA300 Series Pneumatic Scotch Yoke Actuator

Overview

The Bettis CBA300 is a compact pneumatic scotch yoke actuator from Emerson for automating quarter-turn ball, butterfly and plug valves in the small and medium torque range. It takes the scotch yoke principle that Bettis is known for on very large valves and packages it in a lightweight ductile iron body that fits tight piping layouts, skid-mounted process units and valve stations where weight and envelope matter. Emerson positions the series as economical and low-maintenance, with double-acting and spring-return versions and a broad set of overrides and trims.

Seven Star LLC supplies the Bettis CBA300 to refineries, gas plants, utilities and fabrication yards in Oman and across the GCC. As a trusted supplier offering engineering support in Muscat, we size the actuator against the valve’s breakaway and running torque, select the spring set for the site air pressure, and coordinate the solenoid valve, limit switch box and mounting kit for each tag.

Operating Principle

Inside the Bettis CBA300, compressed air acts on a piston that moves a guide block and yoke pin along the slot of a yoke fixed to the torque shaft. The changing lever arm of the scotch yoke produces a torque curve that peaks at both ends of the 90 degree stroke, matching the high breakout and seating torque of quarter-turn valves while the lower mid-stroke output suits the reduced running torque. Double-acting units are powered in both directions, while spring-return units use air to drive the stroke and compress the spring, which then returns the valve to its fail-safe position on loss of air.

Emerson highlights that both double-acting and single-acting versions have no moving parts on the outside apart from the position indicator, which makes the actuator safer around personnel and practically maintenance free. Spring-return Bettis CBA300 models can be configured for fail clockwise or fail counterclockwise action, so a single actuator design covers both fail-closed and fail-open valves.

Engineering Design of the Bettis CBA300

The housing and piston of the Bettis CBA300 are ductile iron, giving more strength per kilogram and good corrosion resistance; the pressure vessel quality housing is approved for use under ASME and the Pressure Equipment Directive 2014/68/EU. The power cylinder interior can be coated with Xylan fluoropolymer for lower friction, abrasion resistance and higher efficiency. Springs are high strength carbon steel, shot peened and protected by Tactyl 50, a pliable self-healing coating. Each piston runs on three field replaceable bearings, and the torque shaft has PTFE-coated upper and lower bearings.

Environmental sealing is a core part of the design. The Bettis CBA300 is independently certified to IEC 60529 IP66 and IP67M, with a quad sealed torque shaft, two independent seals on the lower shaft, an outer seal over the large bearing area and a double-lip bidirectional seal at the top. There are no gaskets: the unit is fully O-ring sealed. The top interface is compatible with NAMUR and TopWorx mounting for close-coupled accessories, and integral bidirectional travel stops adjust from 80 to 100 degrees of total travel.

Key Features

The following points summarise why the Bettis CBA300 is chosen for general and critical on-off valve automation.

• Double-acting models deliver guaranteed minimum torque outputs of 835 to 2,333 Nm (7,388 to 20,337 lb-in).
• Spring-return models provide spring ending torques of 286 to 1,182 Nm (2,532 to 10,457 lb-in) for fail-safe service.
• Pneumatic operating pressure ranges from 3 to 10 bar (40 to 150 psig).
• IP66 and IP67M certification with full O-ring sealing protects against water ingress and corrosion.
• Three temperature trims cover standard, high temperature and special low temperature service.
• A blowout-proof jackscrew override, jackscrew with handwheel or M11 hydraulic override can reposition the valve at full rated torque after loss of air.
• FMEDA reporting through exida supports SIL suitability, and a FIELDVUE controller enables partial stroke testing.
• Emerson provides a five-year warranty on materials and workmanship.

Industrial Applications

Typical duties for the Bettis CBA300 include on-off and emergency shutdown ball valves on process units, tank farm isolation valves, fuel gas and utility air lines, and automated butterfly valves on cooling water and fire water systems. In upstream oil and gas facilities it is used on wellhead manifolds, separator inlet and outlet valves and chemical injection skids, where a compact fail-safe actuator is preferred over a much larger unit. The closed loop instrument system recommended by Emerson for high humidity, salt air and corrosive dust conditions is especially relevant to coastal plants.

The Bettis CBA300 also serves petrochemical, chemical, power generation and pulp and paper plants that standardise on scotch yoke technology across their small valve population. Seven Star LLC supports these users in Muscat, Sohar, Salalah and the wider GCC as a trusted supplier, providing complete Bettis CBA300 packages with Fisher or TopWorx accessories and ASCO solenoid valves where the project specification calls for them.

Technical Specifications

The key Bettis CBA300 data published by Emerson is listed below; refer to the CBA300 torque tables for model-specific values.

How to Order

For a quotation on the Bettis CBA300, send Seven Star LLC the valve make, size, torque values, available air pressure and required fail position. Our instrumentation team in Muscat confirms the model and spring set against Emerson torque data and prepares the full actuated valve package, with lead time confirmed at quotation. The CBA300 brochure can be downloaded from this page, and you may also want to review the Fisher FIELDVUE DVC6200 digital valve controller, the ASCO 8210 Series solenoid valve and the Biffi ALGAS spring-return actuator. Contact us for technically checked Bettis supply in Oman and the GCC.