Bray Series 92/93 Pneumatic Rack and Pinion Actuator

Overview

The Bray Series 92/93 is a family of rack and pinion pneumatic actuators for quarter-turn valves. Series 92 is the double acting version, in which air pressure drives the valve both open and closed, while Series 93 is the spring return version, in which air drives the stroke one way and springs return the valve to its fail-safe position when air is lost. Nine body sizes, from size 48 up to size 255, give double acting output torque up to 44,130 lb-in (4,986 Nm), so the Bray Series 92/93 can automate anything from a small threaded ball valve to a large butterfly valve on a main line.

Seven Star LLC supplies the Bray Series 92/93 across the Sultanate of Oman and the GCC as a stand-alone actuator or as a complete automated valve package with solenoid valve, limit switch box or positioner. As a trusted supplier with engineering support in Muscat, we size each actuator against the real valve torque and the available air pressure on site, which avoids the two common problems of an undersized actuator that stalls and an oversized one that wastes air and money.

Operating Principle

Inside the extruded aluminum body of the Bray Series 92/93, two opposed pistons carry gear racks that mesh with a central pinion. When compressed air enters the center chamber, the pistons move apart, the racks turn the pinion and the output shaft rotates. When air enters the end chambers instead, the pistons move together and the shaft turns the other way. Because the two racks act on opposite sides of the pinion, the forces balance and the output is a pure rotation, which keeps side load off the valve stem and its bearings.

In the spring return version of the Bray Series 92/93, sets of springs sit between each piston and its end cap. Air pressure compresses the springs during the air stroke, and when the solenoid valve exhausts the air, the stored spring energy drives the valve back to its safe position without any external power. This makes the Series 93 the natural choice for fail-closed or fail-open emergency isolation. The double acting Series 92 uses air for both directions, which gives a more compact actuator for a given torque, and it is available with 90, 135 or 180 degree rotation, while the Series 93 is available with 90 degree rotation.

Engineering Design of the Bray Series 92/93

The standard Bray Series 92/93 body is extruded aluminum alloy, anodized, with die-cast aluminum end caps protected by a corrosion resistant polyester coating. For harsh or washdown environments, the body and end caps are also offered in 316 stainless steel. Pistons are die-cast aluminum, the output shaft and pinion are zinc plated carbon steel, the bearings and piston guides are acetal, fasteners are stainless steel and springs are coated spring steel. Exterior options include polyester coating, electroless nickel plating, hard anodizing and Bray Seacorr coating, and a stainless steel pinion can be specified.

Each Bray Series 92/93 actuator is fully enclosed and self-contained, with permanently lubricated bearings and guides that minimize maintenance. The bottom flange follows ISO 5211, so the Bray Series 92/93 mounts directly onto Bray valves and other ISO top flanges without external linkages, which reduces misalignment and contamination between valve and actuator. The top of the shaft and the air ports follow the NAMUR standard, allowing solenoid valves, limit switch boxes and positioners to be mounted directly with no external tubing. Travel stops at both the 0 and 90 degree positions can be adjusted from plus five to minus five degrees, and extended travel stops are available as an option.

Key Features

The following points summarize the design advantages that make the Bray Series 92/93 a common choice for on/off valve automation:

• Opposed piston rack and pinion design that produces balanced, constant torque through the full quarter-turn stroke.
• Double acting Series 92 with 90, 135 or 180 degree rotation, and spring return Series 93 with 90 degree rotation for fail-safe duty.
• Output torque up to 44,130 lb-in (4,986 Nm) across nine sizes from 48 to 255.
• Operating pressure range of 40 to 140 psi (2.8 to 10 bar) on dry compressed air or inert gas.
• Anodized extruded aluminum body with polyester coated end caps, or a full 316 stainless steel construction.
• ISO 5211 mounting for direct valve fitting and NAMUR interface for direct mounting of accessories.
• Integral porting that removes external tubing, which is costly and easily damaged in the field.
• Ingress protection IP66/IP67M per IEC 60529, with ATEX, PED and SIL 3 suitability listed by Bray.

Sizing and Accessories

Bray publishes torque tables for every size and supply pressure. As an example, a double acting size 119 Bray Series 92/93 actuator gives about 2,171 lb-in (245 Nm) at 80 psi (5.5 bar), while the size 255 gives about 29,171 lb-in (3,296 Nm) at the same pressure. Spring return sizing must check both the air stroke and the spring stroke against the valve breakaway and running torque, and it must allow for the lowest air pressure that will be available on site. Approximate 90 degree stroke times range from a quarter of a second on the smaller sizes to about 2.75 seconds on size 255, and they depend strongly on the flow capacity of the solenoid valve and air tubing.

Standard Buna-N seals in the Bray Series 92/93 cover -29 °C to +93 °C (-20 °F to +200 °F). Low temperature seals extend the range down to -40 °C, high temperature seals extend it up to +149 °C, and Bray notes that cycle life is reduced with these special seal kits. Common accessories are Bray Series 63 NAMUR solenoid valves, which mount directly on the integral porting and can be converted between 3-way and 4-way operation, a Series 05 declutchable gear operator for manual override, and limit switch boxes or positioners for position feedback and control.

Industrial Applications

In Oman and the GCC, the Bray Series 92/93 is widely used in water and wastewater treatment, desalination plants, oil and gas utilities, chemical dosing, power plant auxiliaries and bulk material handling. The spring return Series 93 is selected for emergency shutdown and fail-safe isolation where a valve must move to a safe position on loss of air or power, while the double acting Series 92 suits frequent cycling such as filter backwash, tank filling and batch process valves. The coated and stainless steel options help in coastal and industrial zones such as Sohar, Duqm and Salalah, where salt air and heat attack unprotected aluminum.

Seven Star LLC can supply the Bray Series 92/93 mounted on a Bray Series 30/31 resilient-seated butterfly valve as a ready-to-install package. For solenoid control, the actuator works with NAMUR pilot valves such as the ASCO 551 Series NAMUR pilot solenoid valve, and for throttling duty it can be combined with a positioner such as the Rotork YTC YT-1000 electro-pneumatic valve positioner. Our engineers in Muscat confirm torque, air supply, fail position and accessories before quoting, so each Bray Series 92/93 package fits the duty it is bought for.

Technical Specifications

The table below summarizes the Bray Series 92/93 pneumatic actuator according to the Bray technical sales manual and product brochure. Please confirm the exact size and options with our team before ordering.

How to Order

To order the Bray Series 92/93 pneumatic actuator for a project in Oman or the GCC, send a formal RFQ to Seven Star LLC with the valve type, size and torque, the available air pressure, the fail position and the accessories you need. Our instrumentation division in Muscat will confirm the correct actuator size and spring set, check availability and lead time, and send a complete technical offer. The technical sales manual and product brochure are available for download on this page, and our engineers are ready to support you from sizing through commissioning.