IMI STI BW Ultra High Capacity Booster

IMI STI BW ultra high capacity booster: what it is

The IMI STI BW is a pneumatic volume booster built for actuators that need a very large air flow to stroke quickly. It sits between the positioner (or a solenoid and pilot signal) and the actuator, takes a small pilot signal and reproduces it as a high-flow output. The BW is distinguished by carrying two separate regulation screws in one body: one sets how strongly the booster amplifies on the supply side, the other sets the amplification on the exhaust side.

Model name BW is the complete designation; the brochure does not publish a further ordering code for it, so the choices you make are the housing material, the operating-temperature version and the connection arrangement described below. Seven Star LLC, an independent supplier in Muscat, quotes the BW for Oman and the GCC against your duty details.

BW technical specifications

How the BW booster works

A volume booster is a pilot-operated relay. The small signal from a positioner moves an internal element, and that movement opens a large supply port to the actuator or a large exhaust port from it, so the actuator receives or releases air at a flow rate far above what a positioner spool can handle. On the BW the moving element is a metal piston rather than a rubber diaphragm, which removes a wear item and a source of drift in hot or dusty service.

The two regulation screws are what make this booster flexible. Raising the supply setting makes the actuator fill faster; raising the exhaust setting makes it vent faster. Because they are independent, you can speed up the opening stroke without making the closing stroke violent, or the reverse. The brochure notes that the regulation screw cannot be ejected by internal air pressure and can be locked once tuned, which matters on a plant where a setting must survive vibration and routine maintenance.

Where the BW fits in the actuator system

Typical use is on large single or double acting pneumatic actuators driving big ball, butterfly or damper-type final elements, where stroking time with only the positioner would be too slow. The BW is mounted by its machined connection faces with sealing o-rings, so the pipe nipples and fittings that normally join a booster to an actuator are not needed. That shortens the dimensions and removes several leak points.

Within the same IMI STI accessory range the BW is complemented by other volume boosters and by the SC/V linear actuator and SHP positioner families that appear in the manufacturer related-products list. If your application needs a smaller flow or a different footprint, discuss the alternatives with us before finalising the model.

Selection and ordering checklist for BW

• Actuator volume and required full-stroke time, so the Cv of 16 inlet and 20 outlet can be judged against the demand.
• Supply pressure within the 2.5 to 7 bar operating window; the design pressure of 10 bar is a limit, not a working point.
• Aluminium (5 kg) or stainless steel 316 (12.5 kg), depending on corrosion exposure and the support available on the actuator.
• Ambient temperature version: -20 to 70, -40 to 70 or -20 to 85 °C.
• Single or double acting actuator, and whether one or two boosters are needed.
• Whether the exhaust should run through the dedicated protection system model SL or an open manifold exhaust.
• Hazardous area marking, if the valve is in a classified zone; the manufacturer page lists ATEX and IECEx, so confirm the marking on the exact unit.

Installation, tuning and maintenance of the BW

Mount the BW on the matching manifold face with the supplied sealing o-rings seated and the bolts tightened evenly. Connect the pilot signal to the 1/2″ NPT port and supply air to the feeding connection. Use dry, clean instrument air; contaminated air is the most common reason a booster sticks or leaks.

For commissioning, start with both regulation screws at a conservative setting, stroke the valve with the positioner and measure travel time in each direction. Increase the supply screw until the opening time meets the process requirement, then adjust the exhaust screw for the closing time. Stop increasing when the valve starts to overshoot or the positioner begins to hunt, because too much amplification can destabilise the loop. Lock both screws when the result is right and record the final turns for the next technician.

Routine maintenance is mainly keeping the air supply filtered, checking the exhaust path for blockage by dust or insects, and verifying that the screws remain locked. If the process has desert dust, the model SL exhaust protection is worth considering.

Typical applications in Oman and the GCC

Large pneumatic actuators are common on oil and gas isolation and control valves, on power station dampers and on desalination plant butterfly valves, and all of them are exposed to heat and fine dust. The brochure describes the BW as suitable for standard, offshore, sandstorm and copper-free ambient conditions and for low and high ambient temperature, which suits coastal Omani sites with salt-laden air as well as inland desert installations.

Seven Star LLC supplies the BW in Oman and the GCC for refineries, gas processing, petrochemical units and utilities that need a quicker actuator response without replacing the actuator itself.

BW at a glance: what you gain

Information to send with your BW enquiry

• Actuator make, type, size and swept volume, single or double acting.
• Required full-stroke time in each direction.
• Available instrument air pressure and air quality.
• Ambient temperature range and site conditions (offshore, desert, coastal).
• Housing material and hazardous area requirement.
• Quantity and delivery location.

Documents and quotation

A manufacturer brochure for the BW is attached on this page. It carries the technical table and benefits summarised above; the dimensional drawing and instruction manual should be checked before installation.

Send the part number BW with your actuator data and Seven Star LLC will prepare a quotation for Oman and the GCC.