Samson 42-24 Differential Pressure Regulator (Closing)

Samson 42-24 closing differential pressure regulator for flow and return pipes

The Samson 42-24 is a self-operated differential pressure regulator whose valve closes when the differential pressure rises above the set point. It combines the balanced Type 2422 valve with the Type 2424 actuator and is aimed at district heating supply networks, extended heating systems and industrial water or steam circuits. Seven Star LLC supplies the Samson 42-24 in Oman and the GCC as an independent supplier in Muscat.

In the part number, “42” is the series and the last digit pair separates the four differential pressure variants. The 42-24 has an adjustable set point of 0.05 to 10 bar; the 42-28 is the same closing principle with a fixed set point of 0.2, 0.3, 0.4 or 0.5 bar and a Type 2428 actuator. The opening counterparts are the 42-25 and 42-20. If you are unsure which one you need, the deciding question is whether the valve must throttle (close) or release (open) as differential pressure climbs.

42-24 technical specifications

How the 42-24 closes against rising differential pressure

Medium flows through the Type 2422 valve in the direction of the body arrow. The plug position sets the free area between plug and seat, and with it the pressure the valve consumes. A balancing bellows (or, in DN 65 to 250, a balancing diaphragm) cancels the forces of upstream and downstream pressure on the plug, so the actuator only has to deal with the control difference.

Two control lines carry the high pressure (+) and low pressure (–) to the operating diaphragm in the Type 2424 actuator. The diaphragm force acts against the set point springs; once the differential pressure exceeds the setting, the plug moves toward the seat and the valve closes progressively. A seal in the actuator separates the valve pressure from the actuator chamber. In the 42-24 the set point is changed at the adjuster on the actuator, while the 42-28 relies on factory-fitted springs.

Overload protection and the two-diaphragm option of the 42-24

A feature specific to the closing actuators (Types 2424 and 2428) is built-in overload protection. It is a force limiter with an internal excess pressure limiter that opens when the differential pressure exceeds the set point by a fixed amount, which protects the plant and the regulator itself in extreme conditions, such as vacuum forming at a heat exchanger. The response value depends on the actuator area:

For thin oils such as heat transfer oil, or whenever an FKM diaphragm is needed, Samson offers an actuator with two diaphragms and a mechanical rupture indicator that responds at approximately 1.5 bar and shows a red ring. A pressure switch can be added to raise an alarm. After a rupture indication, replacing both diaphragms is recommended.

Where the 42-24 fits in the system

The datasheet shows the 42-24 and 42-28 installed in the return pipe or in the flow pipe of a heating or cooling network, with the control lines picked up across the consumer or substation that is to be protected. A further example is installation in the bypass of a variable-speed pump to keep the minimum pump delivery rate. Related Samson types are the 42-25 and 42-20 (opening), the 42-28 (closing, fixed), and the 42-36 flow regulator for flow limiting. Control lines, needle valves, compensation chambers and fittings are accessories listed in a separate datasheet, and a strainer such as Type 2 NI should be fitted upstream.

Selecting and ordering the 42-24

Send the following information so that the 42-24 can be configured correctly:

• Nominal size DN and balancing principle (bellows for DN 15 to 250, diaphragm for DN 65 to 250; steam only with bellows).
• Pressure rating PN 16, 25 or 40 and body material.
• Set point or set point range in bar and the pipe in which the regulator will be installed (flow or return).
• Medium, operating temperature, maximum operating pressure and maximum differential pressure across the valve.
• Need for compensation chamber, extension piece, two-diaphragm actuator or pressure switch.
• Special versions: ANSI or JIS flanges, deionized water, mineral oils, micro-trim for very small flow, non-ferrous-metal-free design.

The datasheet states that the 42-24 has a leakage class of at most 0.05 % of KVS. If tight shut-off is a safety requirement, a differential pressure regulator is not the right component; a separate shut-off valve should be added.

42-24 valve sizes, KVS and permitted pressure drop

Diaphragm-balanced valves (DN 65 to 250) carry KVS 50, 80, 125, 250, 380, 650 and 800. Sizing follows IEC 60534-2-1 and 2-2 with FL = 0.95 and XT = 0.75. Valve travel is 10 mm up to DN 50, 16 mm for DN 65 to 100 and 22 mm for larger bellows-balanced sizes.

Installation and service notes for the 42-24

Install the valve in a horizontal pipe with the arrow pointing in the flow direction, attach the actuator with its coupling nut, and then connect the control lines. The permissible positions are the same as for the series: suspended is the standard and the only option above 80 °C, sideways is possible for diaphragm-balanced versions and for bellows versions with fixed plug guide, and upright is limited to diaphragm-balanced versions and bellows-balanced DN 15 to 80 up to 80 °C. Flush the line and fit a strainer first, as dirt on the seat will shorten service life. During start-up, open the isolation valves on the control lines slowly to avoid shocking the operating diaphragm. Check the set point after the system warms up, and keep a spare diaphragm and seal set for critical circuits.

Applications of the 42-24 in Oman and the GCC

Closing differential pressure regulators like the 42-24 appear in district cooling and district heating substations, building chilled water risers, hot water systems in hospitals and hotels, and industrial utility networks at refineries, power plants and desalination facilities. In hot and humid coastal sites, the main practical concerns are material compatibility with treated or brackish water, corrosion on the outside of the actuator housing, and keeping control line connections free of salt and sand build-up. Stainless steel bodies and EPDM diaphragms are chosen according to water quality and temperature.

Information to send with a 42-24 RFQ

Quote the part number 42-24, then give DN, PN, material, set point range, medium, temperature and accessories. For replacement of an existing unit, send a photo of the valve and actuator nameplates. Please add the project name, delivery location and any documentation requirement.

Documents and quotation

A Samson datasheet for the 42-24 and 42-28 is attached on this page, covering operation, technical data, materials, KVS values and the ordering text.

Seven Star LLC is an independent supplier in Muscat. Send the part number 42-24 and your process data and we will confirm availability and lead time with your RFQ.