Samson 3256 Series 250 Angle Control Valve DN 15-300

SAMSON Type 3256 angle control valve for demanding process duty

The SAMSON Type 3256 is an angle-pattern control valve from Series 250, designed for process engineering applications with high industrial requirements. The DIN version covers DN 15 to DN 300 and PN 16 to PN 400 with temperatures from -196 to +550 °C. In an angle valve the medium enters from the side and leaves through the bottom, so the valve doubles as a pipe elbow and handles high pressure drops, flashing and erosive service better than many straight-through designs. Seven Star LLC supplies SAMSON valves in Oman and the GCC as an independent supplier in Muscat.

The 3256-1 is the valve fitted with a Type 3271 pneumatic actuator (350 to 2800 cm²), and the 3256-7 is fitted with a Type 3277 actuator (350 to 750v2 cm²) for integral positioner attachment. A 3256-2 electric version is available on request, and a safety manual for SIL applications is optionally offered.

Type 3256 technical specifications (DIN version)

How the Type 3256 angle valve controls flow

A seat and a plug with plug stem are installed in the valve, and the stem is connected to the actuator stem by clamps and sealed by a packing. The medium flows in the direction of the arrow. When the signal pressure rises, the force on the actuator diaphragm increases and compresses the springs; depending on the direction of action, the actuator stem retracts or extends and the plug moves in the seat. The plug position then determines flow and, with it, the downstream pressure.

With the actuator stem extending, the valve is closed on air failure (fail-close). With the stem retracting, it opens on air failure (fail-open). In a high-pressure letdown station the usual choice is fail-close, but for a cooling or relief duty the opposite may be needed.

Trim options and noise reduction on the 3256

The angle body accepts a wide set of plug designs, which is the main reason it is used in severe duty:

• Balanced plug with PTFE or graphite seal ring, used where high pressure or differential pressure act on the plug; pressure balancing for some sizes applies from PN 63.
• Flow dividers ST 1, ST 2 and ST 3 and AC-1/AC-3 trim for noise reduction, documented in separate SAMSON datasheets. For example, KVS 100 becomes 90 (ST 1), 80 (ST 2) or 75 (ST 3) with a divider fitted.
• Perforated plug for low-noise throttling.
• Ceramic or carbide metal internals with ceramic anti-wear pipe for erosive media.
• Stellite facing on seat and plug, or a solid Stellite plug up to KVS 630.
• Special version for flashing service.
• Bellows seal with test connection, insulating section and heating jacket.

Materials in the Type 3256

For seawater and other aggressive media the datasheet mentions 1.4538, duplex 1.4470 and a nickel-based alloy as special materials, with pressure-temperature data in SAMSON information sheet T 8000-2.

Related Series 250 valves and the ANSI counterpart

The Type 3256 sits beside the Type 3251 globe valve and the Type 3253 three-way valve within Series 250, sharing actuators, accessories and many trim parts. The DIN version described here has an ANSI equivalent covering NPS ½ to 20 and Class 150 to 2500 under another datasheet; for ANSI projects in the Gulf, the Series 290 Type 3296 angle valve is the neighbouring product. Using one actuator family across the plant reduces the spare stock you need to hold.

Selecting and ordering a 3256 angle valve

• DN, PN, end connection (flange or welding) and body material.
• Medium, minimum and maximum temperature, and inlet and outlet pressures at minimum, normal and maximum flow.
• Required KVS, characteristic and leakage class; whether a flow divider, balanced plug or perforated plug is needed.
• Whether an insulating section, bellows seal or heating jacket is required.
• Actuator: 3256-1 or 3256-7, area, bench range and fail-safe direction, plus handwheel if needed.
• Accessories: positioner, limit switches, solenoid valve and any SIL documentation.

Commissioning and care of the 3256

Check that the arrow on the body matches the flow direction, support the valve properly because the bonnet and actuator carry a high centre of gravity, and flush the line first. Adjust the packing after the first thermal cycle if the high-temperature packing is fitted. During service, inspect plug and seat for erosion marks, because angle valves in letdown duty wear first at the seat and guide bushings. Keep spare packing sets, gaskets and a complete trim set for critical positions.

Typical 3256 applications in Oman and the GCC

Angle valves of this type are used on high-pressure gas and condensate letdown in upstream oil and gas facilities, on separator level control, on boiler feedwater and blowdown in power and desalination plants, and on hydrocarbon duties in refineries and petrochemical complexes. Sand in produced fluids, flashing in condensate and the heat of the climate all favour hardened trim, stainless or duplex materials and heavy-duty packing, which are the options the 3256 range provides.

Details to supply with a 3256 RFQ

• Datasheet or process sheet with flow cases and pressures.
• DN, PN, body and trim material, connection standard.
• Actuator, air supply pressure, fail-safe direction and accessories.
• Noise or erosion limits and any special trim wanted.
• Tag number or old nameplate if you are replacing a valve.

Documents and quotation

The SAMSON datasheet T 8065 EN for the Type 3256 is attached on this page and holds the complete KVS tables and dimensions for all pressure ratings.

Send the process data and we will confirm what can be offered in Oman and the GCC.