Flowserve Automax RG Scotch Yoke Pneumatic Actuator

Flowserve Automax RG heavy-duty scotch yoke pneumatic actuator

The Flowserve Automax RG Series is a modular, heavy-duty scotch yoke actuator for quarter-turn valve and damper automation. It is built in double acting and spring return versions, with pneumatic, gas and hydraulic variants, and delivers up to 248,000 Nm of torque. The scotch yoke mechanism converts straight piston movement into rotation, which gives the high breakaway torque that large ball, plug and butterfly valves demand. Seven Star LLC, an independent supplier in Muscat, quotes Automax RG actuators and spares in Oman and the GCC.

RG is a series rather than a single part number. Each actuator is configured through a model code that defines body size, cylinder size, action, spring module, yoke pattern, seal material, manual override, coating and options. This page explains the code so that you can specify the unit correctly.

RG series technical specifications

The whole Automax range spans torques from 2.8 to 248,600 Nm, with the RG covering the heavy end of that span.

How the RG scotch yoke mechanism works

Inside an RG, pressure in the cylinder pushes a piston and rod. The rod drives a slider block that runs in the slot of a yoke, and the yoke rotates the output shaft through 90 degrees. Because the geometry gives very high torque at the start and end of travel, where a valve needs the most force to unseat or tightly seat, the scotch yoke suits ball, plug and large butterfly valves, and is why the design is common on large valves.

Quality details matter in service. The cylinder walls are heavy and honed, then hard chrome plated, and the piston carries dynamic quad seals and guide bands that wipe the wall while supporting the piston. A steel guide bar carries the transverse load, PTFE-lined bronze rod bearings support the piston rod, and induction-hardened, chrome-plated yoke pins run in aluminum bronze slider blocks to limit contact stress. Bidirectional travel stops allow open and closed positions to be set precisely.

In spring return models, a pull-to-compress spring module with concentric nested springs sits at one end. The spring provides the fail-safe stroke when air is lost, and its torque stays consistent over the cycle life. The pull rod is oversized and chrome plated.

Where the RG fits: modules, overrides and related actuators

The RG is built from three modules: pressure, torque and spring. This modular design lets one torque module accept pneumatic or hydraulic pressure modules, and lets a double acting unit be converted to spring return. Override options include direct drive jackscrew, bevel gear jackscrew and hydraulic override, and the spring module is designed so that jackscrews or hydraulic overrides can be fitted in the field. A dual cylinder (DD) double acting version is also available.

Smaller quarter-turn duties normally go to other Automax actuator ranges, while the RG is selected when the torque requirement or the need for a robust fail-safe solution is high. Control accessories include NAMUR solenoid valves, limit switch boxes, positioners and lockout modules, which attach to the standard mounting pads.

RG model code and selection checklist

The brochure defines the RG model code in order: series (body size 1 to 8), cylinder size, action, spring module (0 to 8), torque pattern, sealing and temperature, manual override, material or coating, and options. A typical code reads RG 5 22 SR 6 C N D GE TC. The main fields are:

• Action: DA double acting single cylinder, DD double acting dual cylinder, SR spring return fail clockwise, SO spring return fail counterclockwise.
• Yoke: S symmetrical or C canted.
• Seal and temperature: N nitrile, -29 to 82 °C (-20 to 180 °F); H high temperature Viton, -18 to 149 °C (0 to 300 °F); L low temperature, -48 to 82 °C (-55 to 180 °F).
• Manual override: none, G sandwich declutch gearbox, J jackscrew, D bevel gear jackscrew, H hydraulic.
• Coating: GE grey epoxy (standard), PO primer only, WE white epoxy, SP special.
• Options: none, external stopper for clockwise, counterclockwise or both directions, or a special code.

Beyond the code, size the unit with the valve breakaway, running and seating torques plus a safety margin, and the minimum supply pressure that will actually be available at the actuator.

RG installation, commissioning and maintenance

Mount the RG on the valve using the ISO or NAMUR bracket and coupling the project requires, with the actuator and valve in the same position, and align the output so that no side load acts on the stem. Check the supply pressure and filter quality, since clean, dry air extends seal life. Set the travel stops with the valve at fully open and fully closed, then record stroke times and confirm the fail position by cutting the supply to a spring return unit.

Maintenance covers periodic lubrication as defined by the manufacturer, visual inspection of the external retention rods that give visible confirmation of rod integrity, and replacement of seals at overhaul. Keep spare seal kits, guide bands and bearings for critical valves, and note the full model code when ordering. Because overrides and spring modules can be retrofitted in the field, a plant can adapt units as requirements change.

Typical RG applications in Oman and the GCC

The RG is suited to large isolation and emergency shutdown valves on pipelines, tank farms, gas processing and refinery units, as well as large dampers and process valves in power and desalination plants. With a marine-grade epoxy paint system suitable for chemical, coastal and offshore sites, the actuator copes with salt-laden coastal air common in Gulf locations.

Heat, dust and humidity affect the whole control chain, so specify the sealing and temperature code carefully and protect the pneumatic supply with suitable filtration and drying. Where SIL-rated loops or hazardous areas are involved, state this at enquiry so that the correct certification documents can be requested.

RG body size and dimension summary

These are selected actuator dimensions from the brochure; other dimensions, cylinder sizes from 5 to 40 inch and weights depend on the configuration, so request a certified drawing for installation design.

Information to send with an RG RFQ

Send the valve type and size, valve torque data, supply pressure, required action and fail direction, ambient temperature range, mounting standard, accessories, hazardous area and SIL requirements, and the project specification. For a replacement, add the full model code from the nameplate and the serial number, or photos if the plate is unreadable.

Documents and quotation

The Automax RG Series brochure is attached on this page. It includes the feature description, dimensions and the model code explained above.

Seven Star LLC is an independent supplier in Muscat serving Oman and the GCC. Send your RG requirement and we will reply with a quotation.