SAMSON Type 3767 Electropneumatic Positioner
Overview
The SAMSON Type 3767 is an electropneumatic positioner that converts a 0/4 to 20 mA or 1 to 5 mA control signal into an exact valve position on pneumatic control valves. Unlike simpler single-acting units, it can serve single-acting actuators and, with a reversing amplifier, double-acting actuators that need two opposed signal pressures. It handles linear valves with rated travels from 7.5 to 120 mm and rotary valves with opening angles up to 90 degrees, which makes the SAMSON Type 3767 one of the most versatile analog positioners in the SAMSON range. The companion Type 3766 is the pneumatic version for a 0.2 to 1 bar input.
Seven Star LLC supplies the SAMSON Type 3767 with mounting kits, limit contacts and solenoid valve options to engineering contractors, valve workshops and plant maintenance teams in Muscat, the wider Sultanate of Oman and the GCC. We provide engineering support in Muscat for selecting the correct version code, lever and range spring for each valve.
Operating Principle
The SAMSON Type 3767 works on the force-balance principle. The incoming current is converted by the built-in i/p converter into a proportional pressure pe, which acts on a measuring diaphragm made of fluorosilicone. At the same time, the valve travel is transferred through a pin to the pick-up lever and sets the force of the range spring. If the control signal or the valve position changes, the diaphragm lever (flapper plate) moves relative to one of two nozzles, depending on the selected direction of action. This changes the pressure upstream of a booster, and the booster delivers signal pressure pst through a volume restriction to the actuator until the forces are in balance again.
Two adjustable restrictions are used to optimise the loop: the Xp restriction sets the proportional band between 0.5 and 2.5%, and the volume restriction adapts air delivery to the actuator size. A pressure regulator feeds the nozzle system, so the influence of supply pressure is negligibly small, at 1% or less between 1.4 and 6 bar. SAMSON specifies no effect of vibration between 10 and 150 Hz at 4 g, which is why the SAMSON Type 3767 is used on pumps, compressors and piping with strong vibration.
Engineering Design of the SAMSON Type 3767
The SAMSON Type 3767 housing is chromated, plastic coated die-cast aluminium with stainless steel external parts (1.4571 and 1.4305), weighing about 1 kg and rated IP 54, or IP 65 and NEMA 4X with a filter check valve. Three attachment methods are available: direct attachment to the SAMSON Type 3277 actuator for travels of 7.5 to 30 mm, NAMUR attachment to IEC 60534-6 for travels up to 120 mm, and attachment to rotary actuators according to VDI/VDE 3845 with a cam disk for 70, 75 or 90 degrees. Direct attachment gives a tight mechanical connection, a protected travel pick-off and internal air routing to the actuator, so the actuator and positioner can be delivered as a ready-adjusted unit.
The interior can hold additional equipment. Two inductive proximity switches type SJ2-SN act as limit contacts with hysteresis of 1% or less. Alternatively, a built-in solenoid valve for 6, 12 or 24 V DC binary signals vents the actuator and drives the valve to its fail-safe position whenever the signal is removed, regardless of the positioner output. Signal pressure can be limited between approximately 2.5 bar and 6 bar, and pressure gauges for supply and signal pressure can be fitted.
Key Features
Key features of the SAMSON Type 3767 described in SAMSON data sheet T 8355 are:
- Two-wire input of 0/4 to 20 mA or 1 to 5 mA with reverse polarity protection.
- Single-acting or double-acting operation using a reversing amplifier.
- Travel from 7.5 to 120 mm on linear valves and up to 90 degrees on rotary valves.
- Direct attachment to SAMSON Type 3277 actuators, NAMUR rib attachment and VDI/VDE 3845 rotary attachment.
- Linear characteristic with terminal-based conformity of 1% or better, hysteresis of 0.6% or less and sensitivity of 0.1% or less.
- No effect of vibration between 10 and 150 Hz at 4 g.
- Optional inductive limit contacts or an integrated solenoid valve for forced venting.
- Intrinsically safe II 2G Ex ia IIC T6, IECEx, CSA and FM versions, plus Ex nA for Zone 2.
Industrial Applications
Because one device covers globe valves, three-way valves, butterfly valves and ball valves, the SAMSON Type 3767 is common in mixed valve fleets where maintenance teams want a single positioner model and spare parts set. Typical loops include steam and condensate control, heat exchanger temperature control, separator and drum level control, compressor anti-surge bypass valves, fuel gas pressure control and chemical dosing. The integrated solenoid valve option is useful on valves that must move to a safe position on a trip signal while still being modulated in normal service, and the SAMSON Type 3767 limit contacts provide open and closed feedback to the control system.
In Oman and the GCC, the SAMSON Type 3767 is installed in upstream gas plants, refineries, petrochemical complexes in Sohar and Duqm, power and water plants and district cooling networks. Its tolerance of vibration and wide ambient range, down to −40 °C with a metal cable gland and up to 80 °C, suit outdoor installation in hot coastal and desert areas when protected from direct sun. Seven Star LLC supplies the SAMSON Type 3767 for new valve packages and like-for-like replacements, and can match mounting parts for SAMSON and other valve makes.
Technical Specifications
The SAMSON Type 3767 data below are taken from SAMSON data sheet T 8355 EN (edition September 2021).
| Parameter | Specification |
|---|---|
| Model | SAMSON Type 3767 electropneumatic positioner |
| Travel range | Direct attachment to Type 3277: 7.5 to 30 mm; IEC 60534 (NAMUR): 7.5 to 120 mm |
| Opening angle | 70, 75 or 90 degrees depending on cam disk |
| Reference variable | 0/4 to 20 mA (span 8 to 20 mA, Ri 200 ohm) or 1 to 5 mA (span 2 to 4 mA, Ri 880 ohm) |
| Supply air | 1.4 to 6 bar (20 to 90 psi); ISO 8573-1 classes 4/3/3 |
| Signal pressure | Limitable between 0 to approx. 2.5 bar and 0 to 6 bar |
| Characteristic | Linear; terminal-based conformity 1% or better |
| Hysteresis / sensitivity | 0.6% or less / 0.1% or less |
| Proportional band Xp | 0.5 to 2.5% (Kp above 200 to 40) |
| Air consumption | 280 ln/h or less |
| Air output | Supply 3.0 mn³/h at 1.4 bar, 8.5 mn³/h at 6 bar; exhaust 4.5 / 14.0 mn³/h |
| Ambient temperature | −20 to 80 °C standard; −40 to 80 °C with metal cable gland; −45 to 80 °C low-temperature version |
| Explosion protection | II 2G Ex ia IIC T6 (PTB 01 ATEX 2167); IECEx; CSA; FM; II 3G Ex nA II T6 |
| Degree of protection | IP 54; IP 65 and NEMA 4X with filter check valve |
| Materials / weight | Die-cast aluminium; stainless steel external parts; FVMQ diaphragm; approx. 1 kg |
How to Order
For a quotation on the SAMSON Type 3767, send Seven Star LLC the article code or your input signal, valve type, travel or rotation angle, actuator and any options such as limit contacts or a solenoid valve. The SAMSON data sheet T 8355 can be downloaded from this page. Seven Star LLC supplies SAMSON positioners and valves in Oman and the GCC with engineering support in Muscat. See also the SAMSON TROVIS 3730-1 Electropneumatic Positioner, the SAMSON Type 3241 Globe Control Valve and the SAMSON Type 3277 Pneumatic Actuator for Integral Positioner Attachment.
- Datasheet SAMSON Type 3766 / Type 3767 Positioner Data Sheet T 8355 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.
Reviews
There are no reviews yet.