IMI STI SA-1 Analog Valve Positioner, Pneumatic and EP

IMI STI SA-1 analog valve positioner, pneumatic and electro-pneumatic

The IMI STI SA-1 is an analog positioner that makes a pneumatic actuator follow a control signal. It is offered as a pneumatic version, which takes a 3-15 psi (0.2-1 bar) signal, and as an electro-pneumatic version, SA-1-EP, which takes 4-20 mA. Seven Star LLC supplies the SA-1 in Oman and the GCC as an independent supplier in Muscat, and this page sets out the verified specification to help you prepare an enquiry.

The manufacturer describes the SA-1 as heavy duty and suitable for very harsh conditions. It is used as the control element of pneumatic valve assemblies in oil and gas, refining, chemical, power and metal production, and in other plants with automated systems. It is compact enough to be fully installed on a servo-control system, and the brochure points out that it is especially suited to pump use.

SA-1 versions and how to tell them apart

The brochure does not publish a coded ordering string, so the version, housing, characterisation and any hazardous-area option must be confirmed with the exact tag data when you request a quotation.

SA-1 technical specifications

How the SA-1 positions the actuator

The SA-1 works on the balanced-forces principle. The input signal produces a force that is compared with the force of a feedback spring. The spring has a linear characteristic and is moved directly by the piston, so no external linkage, lever or cam is needed to bring the position back to the positioner. When the two forces differ, the spool shifts and routes supply air to one side of the actuator and exhausts the other, until the forces balance again at the commanded position.

In the electro-pneumatic version an I/P converter is mounted on the pneumatic positioner, which turns the 4-20 mA current into a pneumatic pilot for the same mechanism. The positioner is double acting by design, but can be used as single acting.

Stroke range and actuator compatibility of the SA-1

The brochure gives two stroke statements that need to be read carefully. The operational stroke for reverse action with the spring extended is 3-100 mm. The standard operational stroke is 2-65 mm for both direct and reverse action, with a compressed cylinder spring of a maximum diameter of 200 mm. The positioner can be fitted on single or double acting actuators, and split-range operation is among the listed features.

Special characterisation or range can be supplied, and a full stainless steel spool valve is available as an option. Related IMI STI parts in the same ranges include the SmarTrak ST controller for hydraulic systems and accessories such as the CS quick exhaust valve and CF fast commutator.

Selection and ordering checklist for the SA-1

• Signal: pneumatic 3-15 psi or electro-pneumatic 4-20 mA.
• Actuator type: single or double acting, and stroke in millimetres.
• Direct or reverse action, and the spring arrangement of the actuator.
• Hazardous area need: intrinsically safe or explosion-proof electro-pneumatic version.
• Spool valve material: standard or full stainless steel.
• Any special characterisation, range or split-range requirement.
• Ambient temperature range, with -40°C to +85°C available on request.
• Pressure gauges, listed as optional accessories.

Installation, commissioning and maintenance of the SA-1

Supply the SA-1 with clean, dry instrument air between 2.5 and 7 bar, filtered upstream, because the spool valve depends on it. Static air consumption is 1.02 Nm³/h at 400 kPa, which is useful for sizing the air header on a plant with many positioners.

Commissioning involves setting zero and span against the actuator stroke and checking linearity and hysteresis at several points. For the electro-pneumatic version, check the 4-20 mA loop and the conduit entry seal to keep the IP65 rating. Maintenance consists of regular checks of the air quality, inspection for leaks at the connections and keeping a spare unit or I/P converter for critical valves. The manufacturer issues an instruction manual for the SA-1 which should guide service work.

Typical SA-1 applications in Oman and the GCC

Analog positioners remain common on control valves and dampers in plants that value simple, rugged equipment. In Oman and the Gulf the SA-1 fits refining, petrochemical, power and process industry installations where dust, heat and humidity are routine. The aluminium housing with IP65 protection and the sandstorm and copper-free ambient options listed in the brochure address those conditions, and the lack of external feedback parts removes a common source of mechanical wear and misalignment.

Information to send with an SA-1 RFQ

• Part number SA-1 and quantity.
• Pneumatic or electro-pneumatic version.
• Actuator make, model, stroke and action.
• Hazardous area classification, if any.
• Supply pressure and ambient temperature.
• Optional gauges or special characterisation.
• Delivery location in Oman or the GCC.

Documents and quotation

The IMI STI brochure covering the SA-1 is attached on this page. It includes the specification table and dimensional drawing.

To request a quotation, send the part number, version, quantity and actuator details, and we will confirm availability and lead time.