SAMSON Type 4763 Electropneumatic Positioner
Overview
The SAMSON Type 4763 is a single-acting electropneumatic positioner for attachment to pneumatic linear control valves. It receives an electric reference variable from a controller or DCS, typically 4 to 20 mA, compares it with the actual valve travel and delivers the signal pressure that drives the actuator to the matching position. SAMSON describes the design as compact, low maintenance, insusceptible to mechanical vibration and usable in any mounting position, which explains why the SAMSON Type 4763 has been installed for decades on globe valves in refineries, chemical plants, power stations and utility systems. Its sister model, the Type 4765, is the purely pneumatic version for a 0.2 to 1 bar input, and a Type 4765 can be upgraded to a Type 4763 by adding the i/p converter module.
SAMSON now lists the SAMSON Type 4763 as a discontinued product, but a large installed base remains in service across the Gulf. Seven Star LLC supplies the SAMSON Type 4763 and its documentation to maintenance and reliability teams in Muscat, across the Sultanate of Oman and the GCC, helping plants keep existing valve assemblies running and plan migration to current SAMSON positioners. We provide engineering support in Muscat for identification, ordering and replacement.
Operating Principle
The SAMSON Type 4763 uses a flapper-nozzle system that works on the force-balance principle. The incoming current is first converted into a proportional pneumatic signal by the built-in i/p converter module (Type 6109 or Type 6112). This pressure acts on a measuring element, while the valve travel is fed back through a lever and range spring. When the force from the reference variable and the force from the travel feedback are not in balance, the flapper moves relative to the nozzle, the pneumatic amplifier changes the signal pressure pst, and the actuator stem moves until balance is restored. The result is a fixed, linear assignment of valve position x to reference variable w.
The direction of action is selected by turning the nozzle assembly through 180 degrees, giving increasing/increasing (direct action) or increasing/decreasing (reverse action) behaviour. Because the fail-safe action of the actuator (stem extends or stem retracts) and the direction of action determine which side the positioner is attached on, the data sheet shows four basic mounting arrangements. The SAMSON Type 4763 is suitable for normal operation and for split-range operation, where two valves share one controller output, each using 0 to 50% or 50 to 100% of the signal span for travels up to 50 mm.
Engineering Design of the SAMSON Type 4763
The SAMSON Type 4763 housing is die-cast aluminium, chromated and plastic coated, with external parts in stainless steel, and weighs approximately 1.2 kg. The degree of protection is IP 54, or IP 65 when venting through the optional check valve 1790-7408. A version with two pressure gauges allows supply air and signal pressure to be monitored at the valve. Attachment follows IEC 60534-6 and the NAMUR recommendation, so the positioner fits valves with cast yokes such as SAMSON Series 240 as well as rod-type yokes, using the mounting parts specified for each actuator.
Travel is matched with a lever and one of three range springs: spring 1 for 15 mm, spring 2 for 30 mm (or 15 mm split range) and spring 3 for 60 mm (or 30 mm split range). With the lever extension the SAMSON Type 4763 covers rated travels from 7.5 mm up to 90 mm. Pneumatic connections are G 1/4, 1/4-18 NPT or Rc 1/4, and the electrical connection uses a G 1/2 or M20 x 1.5 cable gland in plastic, metal or nickel-plated brass. The proportional band and the air output capacity are both adjustable, so the positioner can be tuned for small fast actuators or large slow ones.
Key Features
Key features of the SAMSON Type 4763 listed in SAMSON data sheet T 8359 are:
- Electric reference variable of 4 to 20 mA, 0 to 20 mA or 1 to 5 mA, with split-range capability.
- Rated travel from 7.5 to 60 mm, extended to 90 mm with the lever extension.
- Force-balance flapper-nozzle design that is insusceptible to mechanical vibration.
- Reversible direction of action by turning the nozzle assembly through 180 degrees.
- Adjustable proportional band and adjustable air output capacity.
- Low air consumption, from 0.19 mn³/h at 1.4 bar supply to 0.5 mn³/h at 6 bar.
- Intrinsically safe Ex ia IIC T6 version (Type 4763-1) and Ex nA version (Type 4763-8).
- Optional pressure gauges for supply air and signal pressure in a stainless steel gauge housing.
Industrial Applications
The SAMSON Type 4763 is typically mounted on SAMSON Type 3241 and Type 3251 globe valves with Type 3271 or Type 3277 actuators, and on other linear valves with NAMUR attachment. Typical duties include temperature control on heat exchangers, steam pressure reduction, level control on separators and tanks, feedwater and condensate control in boiler houses, and flow control in chemical dosing and water treatment. Its simple mechanical design and tolerance of vibration make the SAMSON Type 4763 popular on skids, pump discharge lines and older control loops where an analog 4 to 20 mA signal is still the standard.
In Oman and the GCC the SAMSON Type 4763 is found in oil and gas processing facilities, refineries, petrochemical plants in Sohar, power and desalination plants and district cooling stations. When one of these positioners fails, the quickest route is often a like-for-like replacement with the same article code, lever and spring, so the valve can be returned to service without new mounting parts or recalibration of the loop. Seven Star LLC supplies the SAMSON Type 4763 for these replacement needs, and can also advise on current SAMSON positioners where a migration is preferred.
Technical Specifications
The SAMSON Type 4763 technical data below are taken from SAMSON data sheet T 8359 EN (edition March 2018).
| Parameter | Specification |
|---|---|
| Model | SAMSON Type 4763 electropneumatic positioner, single-acting |
| Versions | 4763-0 without Ex protection; 4763-1 Ex ia (ATEX, EAC); 4763-3 Ex ia (CSA, FM); 4763-8 Ex nA |
| Reference variable | 4 to 20 mA (Ex, Ri = 250 ohm); 4 to 20 mA or 0 to 20 mA (Ri = 200 ohm); 1 to 5 mA (Ri = 880 ohm) |
| Travel range | 7.5 to 60 mm; 7.5 to 90 mm with lever extension |
| Supply air | 1.4 to 6 bar (20 to 90 psi); air quality to ISO 8573-1 classes 4/3/3 |
| Signal pressure | Max. 0 to 6.0 bar (0 to 90 psi) |
| Characteristic | Linear; deviation to terminal point method 1.5% or better |
| Hysteresis / sensitivity | Below 0.5% / below 0.1% |
| Proportional band Xp | 1 to 3.0% (spring 1), 1 to 2.0% (spring 2), 1 to 1.5% (spring 3) at 1.4 bar supply |
| Air output | 3.0 mn³/h at 1.4 bar; 8.5 mn³/h at 6 bar |
| Transit time (Type 3271, stem extends) | 240 cm²: 1.8 s or less; 350 cm²: 2.5 s or less; 700 cm²: 10 s or less |
| Ambient temperature | Type 6109 converter: −20 to +70 °C; Type 6112 converter: −20 to +80 °C (down to −45 °C special version) |
| Explosion protection | II 2G Ex ia IIC T6 Gb (PTB 02 ATEX 2078); II 3G Ex nA ic IIC T6 Gc (PTB 03 ATEX 2183 X) |
| Degree of protection | IP 54; IP 65 with check valve venting |
| Materials / weight | Die-cast aluminium, chromated and plastic coated; stainless steel external parts; approx. 1.2 kg |
How to Order
To order a SAMSON Type 4763, send Seven Star LLC the full article code from the nameplate, or the input signal, explosion protection, travel and actuator type, and we will prepare a formal quotation. The SAMSON data sheet T 8359 is available as a download on this page. Seven Star LLC supplies SAMSON control valve equipment in Oman and the GCC with engineering support in Muscat. Related products include the Samson 3730-3 Electropneumatic Smart Positioner, the SAMSON Type 3725 Electropneumatic Positioner and the SAMSON Type 3271 Pneumatic Diaphragm Actuator.
- Datasheet SAMSON Type 4763 / Type 4765 Positioner Data Sheet T 8359 EN (manufacturer) Download
Samson valve, actuator and positioner types
Samson builds a control valve from modules. The Type 3241 globe valve is the general-service body of Series 240, and the Type 3251 is the Series 250 body for higher pressure ratings. Either one is combined with a Type 3271 pneumatic diaphragm actuator or a Type 3277, whose yoke allows the positioner to be attached directly with a concealed travel linkage. The positioners listed are the Type 3725 and the Type 3730 family: the 3730-1 as the basic electropneumatic version, sold in its current generation as TROVIS 3730-1, and the 3730-3 with HART communication and valve diagnostics. Samson also makes PROFIBUS PA and FOUNDATION fieldbus variants in the same family, plus self-operated pressure and temperature regulators.Where Samson valves are used
Samson control valves throttle steam, gas and liquids in chemical and petrochemical units, refineries, gas processing, power stations, water and desalination plants, and food production. Many reach site as part of a skid or package, so the plant instrument team often meets them first when a positioner or actuator needs replacing. We supply these items to end users and contractors throughout the GCC.Ordering Samson parts: what we need
Every Samson device has a nameplate with the type, a configuration ID (Var-ID) and a serial number. A photo of that plate is the surest route to an exact match. Without it, please send:- Valve: type, DN or NPS, pressure rating, body and trim material, Kvs or Cv, plug and seat style, packing and bonnet type
- Actuator: type, effective area in cm², bench range, fail action and travel
- Positioner: full type code including Ex protection, communication and options such as limit switches or position transmitter
Browse Samson products by category: Control Valves, Valve Positioner, Valve Actuator.
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