Samson TROVIS 3793 Smart Valve Positioner with HART

Samson TROVIS 3793 smart positioner with HART

The Samson Type 3793, sold as the TROVIS 3793 electropneumatic positioner, is a smart valve positioner for pneumatic control valves. It compares a 4 to 20 mA set point from the control system with the real valve position and adjusts the air to the actuator until the two agree. It works on single-acting and double-acting actuators, on both linear (stroke) and part-turn (rotary) valves, and carries HART communication, a plain-text display and the EXPERTplus valve diagnostics. Seven Star LLC supplies TROVIS 3793 positioners in Oman and the GCC as an independent supplier in Muscat, and this page sets out how the 3793 is configured and what to confirm before ordering.

The ordering code of the positioner starts with TROVIS 3793 followed by a string of positions that describe explosion protection, housing, communication and options. The 3793 is therefore a platform, and the same base number covers many certified variants. The sections below explain the choices.

3793 positioner technical specifications

How the TROVIS 3793 positions a control valve

A non-contact travel sensor reads the position of the valve stem or rotation of the shaft, and the microcontroller applies a PID algorithm to the difference between this measured position and the 4 to 20 mA set point. If there is a deviation, the pneumatic module vents or fills the actuator through an i/p converter with a downstream spool valve, moving the valve towards the set point. The output can drive one chamber for a single-acting actuator or both chambers for a double-acting actuator, depending on the installed pneumatic modules.

Four initialisation modes let the positioner be commissioned automatically; the substitution mode even permits start-up while the plant is running, without moving the valve. Air capacity can be adjusted in software, and a tight-closing function can be set so that the valve is driven fully shut or open at the ends of the range. Pressure sensors monitor supply and signal pressure, and a temperature sensor and operating hours counter are integrated. Status messages follow NAMUR NE 107, which classifies faults as failure, function check, out of specification or maintenance request.

3793 positioner modules and options

The positioner is built from plug-in modules. Up to two pneumatic modules and two option modules can be fitted, and they arrive installed and connected from the factory. Pneumatic modules are identified by article codes: P3799-0000 is a dummy module that seals the slot when only one pneumatic module is installed; P3799-0001 provides Output 138 and Output 238 for single- or double-acting use; P3799-0002 is Output 138 single-acting; P3799-0003 is Output 238 single-acting; and P3799-0004 is Output 138 with fail-in-place function. The 0000 to 0003 modules carry SIL approval according to IEC 61508.

Option modules (Z3799 codes) add functions such as software limit contacts with NAMUR or PLC outputs, inductive limit contacts, mechanical limit contacts, an analog position transmitter, external position sensors, binary inputs, forced venting, binary output and an analog input. Some are only available on hardware version HV 02.00.xx with firmware FV 01.01.xx, so always quote the hardware and firmware version when you are matching a spare.

3793 mounting on linear and rotary actuators

3793 selection and ordering checklist

• Actuator type: linear or rotary, single-acting or double-acting, and fail-safe action (stem extends or retracts).
• Actuator make and size, and the mounting standard: direct, NAMUR, VDI/VDE 3847 or VDI/VDE 3845.
• Required stroke or angle, and whether the 170° rotary range is needed on request.
• Hazardous area certification: ATEX, IECEx, FM, CCoE, NEPSI or EAC-Ex, with the zone and temperature class needed.
• Housing material: die-cast aluminium or stainless steel for corrosive or marine atmospheres.
• Pneumatic module combination and the air capacity needed for stroking speed.
• Option modules: limit contacts, position transmitter, binary inputs, forced venting, analog input.
• Minimum ambient temperature, including whether metal cable glands and the low-temperature version are needed.
• Hardware and firmware version, if matching an installed positioner.

Explosion protection for the TROVIS 3793

The data sheet lists a wide set of certificates for the 3793, including ATEX intrinsically safe Ex ia for zone 1 and Ex tb dust protection, ATEX Ex nA for zone 2, IECEx, FM intrinsically safe and non-incendive approvals for the US and Canada, and national certificates for China (CCC Ex and NEPSI), India (CCoE) and the Eurasian EAC-Ex and ECAS-Ex schemes. Which of these applies depends on the positioner variant, indicated in the ordering code and on the nameplate, and some certificates apply only to certain hardware and firmware versions. For Oman and GCC projects, ATEX and IECEx are the usual references, but please confirm with your consultant, and send us the certificate and temperature class you need so that the correct variant is matched.

Installation, commissioning and care of the 3793

Fit the correct bracket for the actuator, adjust the lever or coupling wheel to the travel or angle, connect clean, dry instrument air within the stated quality and pressure, and wire the 4 to 20 mA loop. With the air connected, start the automatic initialisation, which determines the end positions and tunes the control loop to the actuator. After initialisation, the positioner enters closed-loop operation immediately. Check travel against the set point at 0, 50 and 100 per cent, and review the diagnostic status on the display.

Maintenance is simple because the module concept allows pneumatic modules and option modules to be exchanged on site. Keep air filters and regulators clean, since particles and oil are the main cause of positioner trouble, and use the EXPERTplus diagnostics to watch for rising friction, leakage and changed travel times before the valve fails. TROVIS-VIEW software can read the configuration over the serial interface, and HART lets a handheld communicator or asset-management system access all parameters. After replacing a unit, record the firmware and hardware version, and re-initialise it on the valve it serves.

Typical 3793 applications in Oman and the GCC

The 3793 serves control valves and on-off valves in oil and gas, gas processing, refining, petrochemical, power and water plants. HART diagnostics and the NE 107 status let a maintenance team see the health of each valve from the control room, which is particularly useful on remote or unmanned sites. The low-temperature versions and metal glands matter less in the Gulf than in cold climates, but the high-temperature limit of +85°C ambient, the IP66 housing and the stainless steel version suit hot, dusty and salt-laden coastal areas. The SIL-capable pneumatic modules and forced venting option allow the positioner to be used on safety-related valves, within the limits given in the manufacturer’s safety documentation.

3793 versus other Samson positioners

Samson offers several positioner families that are sometimes confused with the 3793. This page deals only with the 3793, a HART smart positioner with a modular pneumatic and option design. If your project specifies a different Samson positioner, send us the type number and we will tell you whether we can quote it. Where a legacy positioner is to be replaced, state the actuator, the mounting and the air supply so that bracket and module needs can be matched.

Information to send with your 3793 RFQ

• Complete code or nameplate data from the installed positioner, including hardware and firmware version.
• Valve and actuator make, size, travel or angle and fail-safe direction.
• Hazardous area certificate and temperature class needed.
• Pneumatic module and option module requirements.
• Quantity and delivery location in Oman or the GCC.

Documents and quotation

A datasheet is attached on this page: the Samson data sheet T 8493 EN for the TROVIS 3793 smart positioner, edition February 2026. It lists the technical data, certificates, modules and dimensions.

Seven Star LLC is an independent supplier in Muscat and quotes TROVIS 3793 positioners and modules against the code or duty you send. Reply with the information above and we will confirm availability and lead time.