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Brand: Samson
SAMSON Type 3351 Pneumatic On/off Valve DN 15-100
Description
SAMSON Type 3351 pneumatic on/off valve: tight shut-off for liquids, gases and steam
The SAMSON Type 3351 is a pneumatic on/off valve from Series 240, a combination of a soft-seated globe-style valve and a diaphragm actuator. It is used for tight shut-off of liquids, gases and vapors on utility, steam and process lines, and is offered to DIN (DN 15 to 100, PN 16 to 40) and ANSI (NPS ½ to 4, Class 125, 150 and 300) standards. The plug seal of reinforced PTFE or PEEK achieves leakage class VI. Seven Star LLC supplies Type 3351 valves in Oman and the GCC as an independent supplier in Muscat.
Type 3351 technical specifications
| Parameter | Specification |
|---|---|
| Manufacturer / part number | SAMSON Type 3351 pneumatic on/off valve (Series 240) |
| Valve size | DN 15 to 100 / NPS ½ to 4 |
| Pressure rating | PN 16 to 40 (DIN); Class 125, 150, 300 (ANSI) |
| Medium temperature | −10 to +220 °C (14 to 428 °F) |
| Body materials DIN | Cast iron EN-GJL-250 (PN 16); spheroidal graphite iron EN-GJS-400-18-LT (PN 16, 25); cast steel 1.0619 (PN 16, 25, 40); cast stainless steel 1.4408 |
| Body materials ANSI | Cast iron A126B (Class 125); cast steel A216 WCC (Class 150, 300); cast stainless steel A351 CF8M (Class 150, 300) |
| Flange form | Form B per EN 1092-2 (cast iron); all forms per EN 1092-1; FF per ASME B16.1 or all forms per ASME B16.5 |
| Plug seal | Reinforced PTFE or PEEK soft seal |
| Leakage class | VI per IEC 60534-4 and ANSI/FCI 70-2 |
| Packing | Self-adjusting PTFE V-ring with carbon; adjustable or special packings optional |
| Actuator diaphragm | NBR, EPDM or FKM with fabric reinforcement |
| Ambient temperature (diaphragm) | NBR −35 to +100 °C; EPDM −40 to +150 °C; FKM −25 to +200 °C |
| Maximum supply pressure | 8 bar (116 psi) for DN 15 to 80; 6 bar (88 psi) for DN 100 |
| Fail-safe action | Fail-close or fail-open |
How the Type 3351 operates
Depending on the plug arrangement and spring location, the valve closes (fail-close) or opens (fail-open) when control pressure falls or supply air is lost. Flow direction matters. For fail-close valves on steam and gas, flow is normally to close (A to B), except at DN 100 / NPS 4 where flow must be to open (B to A). Liquids in fail-close valves also flow to open (B to A). Every fail-open valve passes media in the flow-to-open direction (A to B). Install according to the arrows on the body, because the flow direction is part of the valve’s rated design.
Flow coefficients, actuators and differential pressure
| Size | KVS | CV |
|---|---|---|
| DN 15 / NPS ½ | 6.3 | 7.5 |
| DN 20 / NPS ¾ | 10 | 12 |
| DN 25 / NPS 1 | 14 | 16 |
| DN 32 | 25 | – |
| DN 40 / NPS 1½ | 31 | 36 |
| DN 50 / NPS 2 | 40 | 47 |
| DN 65 / NPS 2½ | 72 | 84 |
| DN 80 / NPS 3 | 90 | 105 |
| DN 100 / NPS 4 | 170 | 200 |
Four actuator sizes are used, from 60 up to 700 cm² with travels between 8 and 30 mm; the DN 100 valve uses the 700 cm² actuator with 30 mm travel. For a fail-close valve with the standard PTFE seal, the minimum control pressure to open at maximum differential is 4 bar (58 psi), and 5.5 bar (80 psi) with PEEK. Permissible differential pressure at DN 15 to 25 is up to 20 bar for gases and vapors (flow A to B), falling to 10 bar for the larger sizes. For liquids with flow B to A it is 16 bar at DN 15 to 25, stepping down to 5 bar for the larger sizes. A reinforced-spring fail-close version raises the limit to 30 bar at DN 15 to 25 with a PTFE seal (flow B to A).
Where the Type 3351 fits and related parts
The Type 3351 is a simple isolation valve rather than a control valve, so it is paired with a solenoid valve for quick action rather than a positioner. The NAMUR adapter plate (order no. 1400-9638 for DN 15 to 80) lets a solenoid valve or pneumatic lock-up valve mount directly without tubing, with versions for Type 3963 and 3967. Related SAMSON models are the Type 3248 cryogenic valve and Type 3510 micro-flow valve; a Type 3351 can also be fitted with limit switches for position feedback.
Dimensions and weights of the Type 3351
| Size | Length L, PN 16/40 (mm) | Weight PN 10/40 (kg, approx.) |
|---|---|---|
| DN 15 / NPS ½ | 130 | 11 |
| DN 25 / NPS 1 | 160 | 12 |
| DN 40 / NPS 1½ | 200 | 26 |
| DN 50 / NPS 2 | 230 | 29 |
| DN 80 / NPS 3 | 310 | 52 |
| DN 100 / NPS 4 | 350 | 70 |
Add roughly 2 kg when a handwheel is fitted. The datasheet lists a minimum clearance for actuator removal (380 mm for small sizes up to 565 mm at DN 100), plus 150 to 210 mm with the handwheel.
Selection and ordering checklist for the Type 3351
- Valve size and pressure rating (PN or Class), and body material from the table.
- Medium (liquid, gas or steam) and temperature, to confirm flow direction.
- Fail-safe action: fail-close or fail-open.
- Available control air pressure, since the minimum depends on differential pressure and seal material.
- Manual override, a PTFE-free version for tobacco or other special duty, and diaphragm material for ambient temperature.
- Accessories: solenoid valve, electric or pneumatic limit switch.
Installation, commissioning and maintenance
Keep the actuator clearance free so it can be removed for service. Use clean, dry control air within the permitted pressure, and filter-regulate it. At commissioning, check that the stroke is complete on both sides of the air signal, and test the shut-off. The packing is self-adjusting; replace the soft plug seal when leakage develops. Spare seal sets and diaphragms are the usual stocking items.
Typical applications in Oman and the GCC
On/off valves like the Type 3351 are common on steam supply to heat exchangers and tracing, boiler and utility headers, fuel gas branches, process water and condensate, and skid-mounted packages. Hot and dusty site conditions favour diaphragm materials suited to high ambient temperatures, and shaded, sealed mounting of solenoid valves.
Information to send with an RFQ for the Type 3351
- DN or NPS, PN or Class and body material.
- Medium, temperature, pressure and differential pressure when open and closed.
- Fail-close or fail-open, available control air pressure, handwheel need.
- Solenoid valve voltage and area classification, limit switches, project specification.
Documents and quotation
The SAMSON T 8039 datasheet for the Type 3351 is attached on this page, with all materials, pressure tables and dimensions.
Send the Type 3351 details and your service data and Seven Star LLC will quote supply to Oman and the GCC.
Datasheets & Documents
- Datasheet SAMSON Type 3351 Datasheet T 8039 Download
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About brand
SAMSON is a German manufacturer of control valves, actuators, positioners and self-operated regulators. Hermann Sandvoss founded the company in Düsseldorf on 1 April 1907, and its first important product was a thermostatic valve that controlled temperature without external power. After moves to Mannheim, SAMSON settled in Frankfurt am Main in 1916, where SAMSON AG is still headquartered.
Seven Star LLC supplies Samson control valves, pneumatic actuators and positioners to process plants in Oman, including the types listed on this page and their replacement units.
Samson company profile
| Founded | 1 April 1907, Düsseldorf, by Hermann Sandvoss, as VULCAN Technische Apparate Baugesellschaft; products sold under the SAMSON name |
|---|---|
| Headquarters | Frankfurt am Main, Germany, since 1916 |
| Legal form | SAMSON AG |
| First product | A self-operated thermostatic valve |
| Group brands | SAMSON together with PFEIFFER, LEUSCH, VETEC and AIR TORQUE |
| Product families | Globe valves such as Type 3241, rotary and butterfly valves, 3271 and 3277 pneumatic actuators, 3730 and 3731 positioners, self-operated pressure and temperature regulators |
Milestones
- 1907: Hermann Sandvoss founds the company in Düsseldorf.
- 1909: It is re-established as SAMSON Apparatebau GmbH.
- 1916: After a period in Mannheim, the company moves to Frankfurt am Main.
- 1975: The name becomes SAMSON Mess- und Regeltechnik.
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.
Among 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.
Samson products we list
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
We check the code against Samson documentation and provide the manufacturer's data sheet on request.
Facts checked against SAMSON's corporate chronicle and press material, October 2026.
Browse Samson products by category: Control Valves, Valve Positioner, Valve Actuator.
FAQ
Questions about the SAMSON Type 3351 Pneumatic On/off Valve DN 15-100
Answers from our engineering team on installation, compatibility and integration.
01What leakage class does the Type 3351 achieve?
Class VI according to IEC 60534-4 and ANSI/FCI 70-2, using a soft-seated plug with reinforced PTFE or PEEK seal.
02What sizes and pressure ratings does the Type 3351 cover?
DN 15 to 100 (NPS ½ to 4) with PN 16 to 40 or ANSI Class 125, 150 and 300, depending on the body material.
03Which flow direction should I use?
It depends on fail-safe action, medium and size. For example, fail-close liquid valves use flow B to A, while fail-close gas and steam valves up to DN 80 use A to B. Fail-open valves always use A to B.
04Can a solenoid valve be mounted directly?
Yes, via a NAMUR adapter plate (order no. 1400-9638 for standard use, DN 15 to 80), without separate tubing.
05What control pressure is needed?
Maximum supply is 8 bar for DN 15 to 80 and 6 bar for DN 100. Minimum control pressure to operate depends on the differential pressure, e.g. 4 bar to open a PTFE-seated fail-close valve at full differential.
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