IMI STI CO 3-Way Pneumatic Operating Valve, 1/4 to 2 in.

IMI STI CO 3-way pneumatic operating valve for trip and shutdown

The IMI STI CO is a pilot-operated 3-way pneumatic valve designed for high-flow duties. It is used to connect an actuator to supply or to exhaust under the command of a small pilot device, typically a solenoid valve or a pneumatic pressure switch, in safety, trip or shutdown arrangements. Seven Star LLC supplies the CO in Oman and the GCC as an independent supplier in Muscat, and this page summarises the verified data to help you prepare an enquiry.

The CO comes in five sizes, 1/4", 1/2", 1", 1 1/2" and 2", so the same operating principle can serve small positioner-sized actuators and large cylinders. More than one CO can be run as synchronous units from one pilot when the required flow is higher than a single valve gives.

CO sizes and what changes between them

CO is a model name; the size and material define the configuration. The brochure values are compared below.

Weights are given in the brochure per size and material, and the dimensional drawings show each version, so ask us for the figures for your size. Materials are anodised aluminium or stainless steel 316 for most sizes, and painted aluminium (RAL 7001) is listed for the largest sizes.

CO technical specifications

How the CO 3-way valve works

A 3-way valve has three connections: supply, the actuator port and exhaust. In the CO, the pilot pressure moves the internal element to select which of the two paths is open to the actuator. Without pilot, the actuator is vented; with pilot, the actuator is connected to supply, or the reverse depending on the arrangement. Because the pilot only needs to move the internal element, a small solenoid valve can command a large CO, and the manufacturer notes that switching stays very fast even when the pilot is a low-CV solenoid.

Using several CO units in parallel as synchronous units gives extra flow capacity. Combined with a solenoid valve, a pressure switch or both, this is how the safety, trip or shutdown functions mentioned in the brochure are built.

Manifold mounting and the wider IMI STI accessory range

The CO uses the same machined manifold face with an o-ring seal as other IMI STI accessories. Fittings and nipples are therefore not needed, which saves assembly time, reduces the number of items in stock and shortens the installed dimensions. In practice this means a CO, a CF fast commutator and a CS quick exhaust valve can be arranged on a common manifold without improvised piping.

Where the application needs only venting, the CS two-way quick exhaust valve is the simpler part. Where fast switching of two chambers on a double-acting actuator is needed, the CF is intended. The CO is the general-purpose, high-flow 3-way element in this set.

Selection and ordering checklist for the CO

• Size, chosen from the required CV and the actuator volume and stroke time.
• Material: aluminium or stainless steel 316 according to atmosphere and corrosion exposure.
• Ambient temperature band, one of the three standard ranges or a special request.
• Port type: threaded or manifold mounting, noting the larger sizes list manifold options.
• Pilot source: solenoid valve, pressure switch or both, and the pilot pressure available.
• Single or double acting actuator, and how many CO units operate together.
• Supply pressure within 2.5 to 7 bar.
• Ambient condition: standard, offshore, sandstorm or copper-free.

Installation, commissioning and maintenance of the CO

Mount the valve on its manifold face with new o-rings or connect to NPT ports with suitable thread sealant. Keep the pilot line short and clean, and check that the exhaust port is not obstructed. When several units work in parallel, connect their pilot ports to a common pilot so they switch together.

At commissioning, trip the system from its real source and check that the actuator reaches its safe position within the required time. Repeat on a schedule defined by your safety procedures. Typical faults are leakage at the manifold faces, contamination from poor air quality and slow switching caused by restricted pilot lines. The manufacturer issues an instruction manual for the CO, which should be used for service steps and spare parts.

Typical CO applications in Oman and the GCC

3-way pneumatic operating valves are used on shutdown and isolation valves in oil and gas production, gas processing and refining, on boiler and turbine services in power plants, and on critical on/off actuators in petrochemical and desalination plants. In the Gulf, the material choice matters because of salt, humidity and dust, and the temperature options matter because of summer ambient extremes. The brochure lists suitability for standard, offshore, sandstorm and copper-free conditions.

Information to send with a CO RFQ

• Part number CO and quantity.
• Size and housing material.
• Port style and pilot arrangement.
• Actuator type, volume and required stroke time.
• Supply pressure and ambient temperature range.
• Hazardous area or SIL requirements for the loop.
• Delivery location in Oman or the GCC.

Documents and quotation

The IMI STI brochure for the CO is attached on this page. It includes the size table and the dimensional drawings for each size.

To request a quotation, send the part number, size, material and quantity, and we will confirm availability and lead time.