Samson Type 42-34 Differential Pressure Regulator DN 15-250

Samson Type 42-34 differential pressure regulator with flow limitation

The Samson Type 42-34 is a self-operated differential pressure regulator with an adjustable flow limiter for larger pipe sizes. The datasheet T 3013 covers it together with the Type 42-38 and gives nominal sizes DN 15 to 250, pressure ratings PN 16 to 40, differential pressure set points from 0.1 to 2.5 bar and liquids from 5 to 150 °C. The valve closes as the differential pressure rises, and the flow rate is limited at an adjustable restriction. Seven Star LLC supplies the Type 42-34 in Oman and the GCC as an independent supplier in Muscat for chilled-water, hot-water and glycol circuits.

Where the Type 46-6 on this site is a compact regulator in red brass up to DN 50, the 42-34 is the large-bore choice: it can be built up to DN 250 with a cast iron, spheroidal graphite iron or cast steel body, and from DN 125 upward it has a fixed plug guide as standard, which suits installation in riser pipes.

Type 42-34 versus Type 42-38

The 42-34 DoT and 42-28 types listed separately on the Samson site follow other datasheets and are not covered here.

Type 42-34 technical specifications

How the 42-34 limits flow and holds differential pressure

The medium passes through the valve in the direction of the arrow. The restriction and the plug together set the flow and the differential pressure. The high pressure is passed through a control line to the bottom diaphragm chamber of the actuator, and the pressure downstream of the restriction goes through the hollow plug stem and a control line to the top. The resulting differential is converted into a positioning force that moves the plug against the set point springs. A flow set point adjustment moves the restriction to fix the maximum flow. The plug is balanced by a stainless steel bellows or by a balancing diaphragm, which cancels the forces of inlet and outlet pressure on the plug.

Where the 42-34 fits in a system

Typical position is the return pipe of a substation or riser. The datasheet lists accessories such as compression fittings, needle valves, equalising tanks and control lines in the separate data sheet T 3095. Other Samson regulators of this kind on this site include the Type 45-1 N and 46-6, the flow regulator 42-36 and the differential pressure regulator 42-24/42-28.

Selection checklist for a Type 42-34

• Differential pressure set point: the sum of the fully open plant pressure drop and the pressure drop across the restriction.
• Maximum flow required, then DN and KVS; check the flow table for 0.2, 0.5 and 1.0 bar plant differential.
• Bellows or diaphragm balancing; fixed plug guide for DN 125 and larger.
• PN 16, 25 or 40 and the body material (cast iron, spheroidal graphite iron or cast steel).
• Temperature: above 150 °C a compensation chamber is needed up to 220 °C.
• Actuator area (160, 320 or 640 cm²) matched to the set point range.
• Accessories from the control line set.

Installation, commissioning and maintenance of the 42-34

Install the regulator in the return pipe with a strainer upstream and the control lines mounted on site according to the mounting instructions. Set the differential pressure at the actuator, set the flow limit at the restriction and vent the actuator and lines as described for bellows-balanced valves DN 125 and larger. Inspect the operating diaphragm, the balancing bellows or diaphragm, and the soft plug seal during planned outages. Because control lines are mounted on site, a leak-free, pressure-tested control line is key to correct operation.

Typical applications of the Type 42-34 in Oman and the GCC

District cooling and heating distribution, large building chilled-water risers, process cooling loops and cooling-water circuits of power and desalination plants use pressure-independent branch control to avoid starving remote users. The size range of the 42-34 matches the large loops common in GCC mixed-use developments and utility plants.

Information to send with your Type 42-34 RFQ

• Medium, temperature and pressure at the regulator.
• Maximum flow, plant pressure drop and required set point.
• DN, PN, flange standard and body material.
• Balancing type and temperature, including compensation chamber if above 150 °C.
• Quantity, tags and delivery site.

Documents and quotation

The Samson data sheet T 3013 covering Types 42-34 and 42-38 is attached on this page. Send your duty data and we will confirm availability and lead time. Seven Star LLC is an independent supplier and does not claim any official status with the manufacturer.