Bray Series 98 Pneumatic Scotch Yoke Actuator, up to 100,000 Nm

Modular scotch yoke actuator for large and high-torque valves

The Bray Series 98 is a modular pneumatic scotch yoke actuator designed for quarter-turn valves that need high torque from a compact unit. A pressure module (pneumatic or hydraulic), a torque module with a symmetrical or canted yoke and, for fail-safe duty, a spring module are combined to match the valve, and Bray quotes a torque output range of 230 to 100,000 Nm (2,038 to 885,100 lb-in) in the datasheet, with spring-end torque from 310 to 50,307 Nm.

In a scotch yoke the piston and springs drive a rotating yoke through a slot and sliding blocks, which gives a torque curve that starts high, dips towards mid-stroke and rises again at the end. That shape matches the break-out and seating demands of many ball, plug and butterfly valves. The canted-yoke option shifts the curve for valves whose seat-break and end-position torques differ.

Technical specifications

Source: Bray datasheet SDS-1057 and the Series 98 brochure. The brochure prints a lower torque limit of 310 Nm; the datasheet value is used here.

Construction details that matter in service

The torque module is a single-piece cast housing with integral travel stops, replaceable self-lubricating PTFE bearings with metal backing and a guided drive that supports side loads, with a relief vent that prevents ingress and over-pressurisation. Pressure modules use corrosion-protected external tie rods, a honed and hard chrome plated cylinder barrel, quad ring and U-cup seals and dual wear bands. Spring modules are fully enclosed and welded for safety, with guided and centred springs, no metal-to-metal contact and Tectyl-coated springs.

Module alignment is held by precision machined centering rings, so the actuator can be reconfigured in the field. For emergency shutdown service Bray lists fast action (under one second), manual and automatic release options and a certified SIL 3 capability per IEC 61508, plus a partial stroke device that allows ESD valve verification without interrupting the process.

Accessories and selection

The Series 98 pairs with Bray accessories that mount directly on the shaft-driven NAMUR interface: the Series 5A to 5C valve status monitors, Series 54 proximity sensors and Series 6A positioner. A hydraulic damper gives cushioning at the end of high-speed strokes to protect the valve seat and piping. Torque is sized from the valve manufacturer’s break-out torque, supply pressure and safety factor, so please send the valve model, size, differential pressure, fail direction and available air supply.

How the Bray Series 98 works

Air pressure moves a piston in the pressure module. The piston pushes a sliding block through the slot of a yoke, and the yoke turns the valve shaft through a quarter turn. In a spring return unit the springs drive the yoke back when the air is removed.

Where the Series 98 is used

• Large ball valves
• Plug valves
• Butterfly valves
• High-torque on and off duty
• Fail-safe valve duty

Selection checklist for the Series 98

• Valve torque at break-out and seating
• Double acting or spring return
• Symmetrical or canted yoke
• Supply pressure
• Air, gas or hydraulic supply
• Ambient temperature
• Override option
• Mounting base size

Installation, commissioning and maintenance notes for the Series 98

Fit the actuator on the valve with the ISO 5211 base. Connect clean, dry air. Set the travel stops at both ends. Cycle the valve and check the stroke time. Grease and inspect the unit at regular intervals.

Requesting a quotation for the Bray Series 98

Please send the valve torque, the supply pressure and the fail action. Seven Star LLC serves industrial customers in Oman and the GCC and replies with a quotation based on the information provided.

Series 98 actuator type

The Series 98 is a modular pneumatic scotch yoke actuator.

Series 98 modules

It combines a pressure module, a torque module and a spring module.

Series 98 torque range

The torque output is 230 to 100,000 Nm.

Series 98 spring torque

Spring-end torque runs from 310 to 50,307 Nm.

Series 98 supply pressure

The supply pressure is 40 to 150 psi.

Series 98 media

Media include dry compressed air, inert gas and natural gas.

Series 98 standard temperature

The standard range is minus 29 to plus 93 degrees C.

Series 98 high temperature

The high range goes up to 149 degrees C.

Series 98 low temperature

The low range goes down to minus 46 degrees C.

Series 98 mounting base

The base follows ISO 5211 with two drilling patterns.

Series 98 accessory mounting

Accessories mount to NAMUR and VDI/VDE shaft-driven patterns.

Series 98 yoke options

The yoke is symmetrical or canted.

Series 98 override options

Overrides include jackscrew and hydraulic types.

Series 98 coating

The standard coating is epoxy and polyurethane.

Actuator records for the Series 98

Record the valve tag, the stroke time and the lubrication dates.

Choosing the right Series 98 yoke

Choose the yoke from the torque curve of the valve.

Documents and quotation

The Bray datasheet is attached; the page also lists a product brochure, installation and operation manual, safety manual and technical sales manual.

See the wider range of valve actuators on our catalogue, or send the model name and order number for a quotation.