DA22F-40P （DAH-15B，DAH-25B）Cryogenic Safety Valves

| Product Overview

The DA22F-40P Series is a family of spring-loaded cryogenic safety valves engineered for overpressure protection in deep-cryogenic systems operating from −196°C to +85°C. This series comprises two size variants—DAH-15B (metering connection M30×1.5) and DAH-25B (metering connection M36×2)—sharing a common vertical, upright, L-type relief architecture. Their function is identical and vital: when system pressure exceeds a preset threshold, they open automatically, vent the excess gas, and reseat once normal pressure is restored, protecting cryogenic storage tanks, dewars, piping, and process vessels from the pressure build-up caused by boil-off, thermal expansion, or upstream over-supply.

The series is built around a deliberate material architecture. The pressure-containing body is stainless steel (S304L), providing deep-cryogenic toughness, excellent impact resistance at −196°C, and corrosion resistance across the full industrial gas spectrum. The seat, disc, and bonnet are brass, offering machinable, dimensionally stable seating hardware, while the sealing element is PTFE, delivering a tight, leak-free closure at cryogenic temperatures where metal-to-metal seats are prone to leakage through differential thermal contraction. This S304L / brass / PTFE combination is field-proven across LOX (liquid oxygen), LIN (liquid nitrogen), LAr (liquid argon), and LNG (liquefied natural gas) service.

Two structural features distinguish this series. First, the swivel connections allow the inlet and outlet to be rotationally adjusted during installation, easing alignment with existing pipework and reducing the risk of imposing torsional stress on the body—a common failure cause in cryogenic systems where pipe contraction and expansion create load paths. Second, the anti-loosening design keeps the adjustment mechanism and fasteners secure under vibration and repeated thermal cycling, so the calibrated set point is preserved over the valve's service life.

The series is rated at 580 psig, with a maximum working pressure of 34.47 bar (500 psig), and the actual relief set point is adjustable within this working window via the spring preload. In addition to ISO 4126 (safety devices for protection against excessive pressure) and TSG ZF001 compliance, the series carries CGA G-4.1 oxygen service certification, qualifying it for oxygen pipeline and medical oxygen applications where material compatibility, cleanliness, and ignition safety are paramount. The spring-loaded, self-reseating design allows reuse across repeated overpressure events, and the vertical upright form factor with side horizontal inlet/outlet suits compact cryogenic skids, manifolds, and space-constrained installations.

| Working Principle

The Closed State — Spring Preload and Leak-Free Sealing:

Inside the valve, a compression spring is preloaded against the disc through the adjustment mechanism. The spring force presses the disc onto the PTFE seat, forming a gas-tight seal between the process side and the discharge side. In this series, the seat, disc, and bonnet are machined in brass while the sealing element is PTFE; this combination provides a conformable, low-leakage closure that compensates for the differential thermal contraction typical of cryogenic service. The preload is set so that the downward spring force balances the upward force exerted by the process pressure acting on the disc area. At normal operating pressure—below the set point—the spring force exceeds the pressure force, and the valve remains closed with zero leakage. The anti-loosening design keeps the adjustment mechanism locked against vibration and thermal cycling, so the preload—and therefore the set point—is preserved over time.

The Opening Event — Decisive Action at the Set Point:

As the system pressure rises—from boil-off accumulation, thermal expansion of trapped liquid, or upstream over-supply—the upward pressure force on the disc increases. When the process pressure reaches the set point, the upward force overcomes the spring preload, and the disc lifts off the PTFE seat with a decisive, full opening. This clean, complete lift—rather than a gradual, leaking simmer—vents the excess pressure promptly and reseats without seat erosion. The vented gas is discharged through the outlet, which is oriented to release safely away from personnel and equipment.

The Reseating Event — Pressure Restored:

Once the overpressure condition is relieved and the system pressure falls below the set point, the spring force again exceeds the pressure force, and the disc is pushed back onto the PTFE seat, re-establishing the gas-tight seal. This self-reseating behavior is the defining advantage of a spring-loaded safety valve: it protects against repeated overpressure events over its service life without replacement, and it vents only the minimum gas required to restore safe pressure.

Set-Point Adjustment:

The opening pressure is determined by the spring preload, adjustable within the series' maximum working pressure window of 34.47 bar (500 psig), up to the 580 psig structural rating. Turning the adjustment mechanism compresses or relaxes the spring, raising or lowering the set point accordingly. In practice the set point is locked, sealed, and tagged after calibration to prevent unauthorized tampering.

Swivel Connections and Upright Installation:

Both the inlet and outlet use rotationally adjustable (swivel) connections. The valve is installed upright with side horizontal inlet and outlet, and the swivel feature lets the installer rotate the connection hardware to align with existing pipework without twisting the body—protecting the valve from the torsional stresses that thermal contraction and expansion can otherwise impose. The metering connections are M30×1.5 (DAH-15B) and M36×2 (DAH-25B), giving a standard, tool-friendly interface for direct installation.

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 Factory Shoot

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 Application Video

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 Product parameters

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Comment & FAQ

1:  What is the DA22F-40P series and which models does it include? 

A: The DA22F-40P series is a family of spring-loaded cryogenic safety valves for overpressure protection in deep-cryogenic systems. It includes two size variants: the DAH-15B with a metering connection of M30×1.5, and the DAH-25B with a metering connection of M36×2. Both share the same vertical, upright, L-type relief architecture, the same S304L / brass / PTFE material combination, the same 580 psig rating with a 34.47 bar (500 psig) maximum working pressure, and the same compliance with ISO 4126, TSG ZF001, and CGA G-4.1 oxygen service certification. The models differ mainly in connection size and flow capacity, so select the size that matches your pipework and required relief capacity.

2.   What are the typical applications of this safety valve series?

A: Typical applications include vapor-space overpressure protection of cryogenic storage tanks, liquid nitrogen dewar relief, oxygen pipeline and manifold overpressure protection, LNG storage and transport facilities, and any low-temperature process requiring automatic pressure venting. Thanks to its CGA G-4.1 oxygen service certification, the series is also specifically qualified for oxygen pipeline and medical oxygen supply systems, where material compatibility, cleanliness, and ignition safety are critical. In short, wherever a cryogenic system can over-pressurize—from boil-off, thermal expansion, or upstream over-supply—this valve provides automatic, reusable protection.

3.  What are swivel connections and why do they help in cryogenic installation?

A: Swivel connections are inlet/outlet joints that can be rotationally adjusted during installation—the connection hardware rotates to align with the mating pipework before being tightened. This matters greatly in cryogenic systems for two reasons. First, it eases alignment: the installer can rotate the connections to match the pipe axis without bending the valve or forcing the pipe, simplifying installation and saving time. Second, it prevents torsional stress: thermal contraction and expansion in cryogenic piping create large load paths, and a fixed connection forces these loads through the valve body. A swivel lets the connection absorb the rotation, protecting the body from stress-induced distortion or failure.

4.   Why is S304L stainless + brass + PTFE a good material combination for cryogenic service?

A: Each material is chosen for its best-performing role. S304L stainless steel forms the pressure-containing body: it delivers deep-cryogenic toughness and impact resistance at −196°C, low-carbon content (the "L") improves weldability and resists sensitization, and it withstands corrosion across the full industrial gas spectrum. Brass forms the seat, disc, and bonnet: it is machinable, dimensionally stable, and retains adequate strength and ductility in the connection and seating zones, giving reliable, repeatable seating geometry. PTFE forms the sealing element: it is the critical low-leakage seal, conforming to the seat to compensate for differential thermal contraction, where metal-to-metal seats would leak. Together they give a valve that is structurally sound, corrosion-resistant, and leak-tight through −196°C to +85°C service.

5.   What does CGA G-4.1 oxygen service certification mean for this valve?

A: CGA G-4.1 is the Compressed Gas Association standard governing the design, material selection, cleanliness, and testing of equipment used in oxygen service. Oxygen is a strong oxidizer—many materials that are perfectly safe in other gases can ignite in oxygen, so equipment must use compatible materials, be rigorously cleaned of contaminants, and be designed to avoid ignition sources. The certification on this series means the valve has been evaluated as suitable for oxygen service: its materials (S304L, brass, PTFE) are oxygen-compatible, and the manufacturing and cleaning meet the standard's requirements. This makes the series suitable not only for liquid oxygen (LOX) systems but also for oxygen pipelines and medical oxygen supply where compliance is mandatory.

6.   What should I consider during installation? 

A: Key installation points: (1) install the valve upright with the inlet/outlet connections properly aligned, using the swivel feature to match pipe axes without twisting the body; (2) use a thread sealant or tape suitable for the service gas and cryogenic temperature; (3) orient the outlet so vented gas is directed away from personnel, equipment, and heat sources, adding a discharge line if needed; (4) support the valve and adjacent pipework so thermal contraction and expansion do not impose bending stress on the body; (5) do not place an isolation valve upstream that blocks pressure transmission (or interlock it per code); (6) for oxygen service, follow the cleanliness and handling requirements of CGA G-4.1 during installation; (7) allow for thermal contraction of connected pipework and provide cryogenic protection to prevent icing affecting operation.