GN 7404

Two-way breathable membranes

Stainless Steel / Aluminium, Oil repellent (oleophobic) / Water repellent (hydrophobic)

GN 7404-AL

Two-way breathable membranes
Aluminum

GN 7404-NI

Two-way breathable membranes
Stainless Steel

GN 7404-AL

Two-way breathable membranes
Aluminum

Body

  • Aluminum AL
  • Stainless Steel AISI 303 NI

Membrane

Non-woven nylon material / Acrylic copolymer wetting

Membrane enclosure

Plastic (Polyamide PA)

  • glass fiber reinforced
  • temperature resistant up to 100 °C

Protective strainer

Stainless Steel AISI 304

Seal / O-Ring

NBR (Perbunan®)

GN 7404 two-way breathable membranes are used when constructing housings and equipment. When installed in the wall of a housing, they can be used to equalize the pressure between the interior of the housing and the surrounding area.

Any dirt, dust, oil, or water in the gaseous medium is kept out. This prevents dirt and moisture from entering the interior of the housing and prevents oil from dripping into the surrounding area.

In order to protect the membranes, they should not be completely covered with oil or water, and the differential pressure/air permeability volume should not be exceeded. They should be installed on the side/vertically in a protected position.

The external Ø of the housing with the recessed hexagon is designed for tapped plates for DIN 3852 tube fittings.

The seal is embedded in a recess on the planar side. This prevents it from being lost and squeezed outwards during the tightening process.

  • Mounting nut GH.

  • Body in brass MS
  • other membrane pore size

The membranes use a non-woven nylon material as a substrate with a completely unordered structure. The minuscule pores of the membrane are created by fully saturating the fibers with an acrylic copolymer, which does not fill the gaps in the material.

The material and process parameters affect the size of the pores during manufacturing, which can be between 0.2 and 10 µm. Porometry can be used to determine the quality of the membrane. This is a rating procedure which assesses, among other things, the distribution of the sizes of the membrane pores and air permeability. A microscopic image of the cross-section of a membrane is shown here.

For comparison: The minimum mesh width of a filter manufactured using economically viable methods is 50 µm.

 

Membrane, microscopic images, 2000x magnification

The membranes repel oil and water because of their materials and surface structure. This prevents water and oil droplets from completely suffusing the membrane surface. These properties are supported by installing the membrane on the side in a vertical position.

If the membrane is covered in exceptional circumstances, small quantities of oil or water can be pushed through the membrane due to the pressure differential. Once the situation has been rectified, the oil and water will drip off and the membrane will be fully functional.

The maximum air permeability volume, the maximum pressure differential, and the maximum rated/burst pressure are all important when using membranes. There is a linear correlation between the air permeability volume which can be achieved and the differential pressure, which should not exceed 1 bar.

Air permeability volume dependent on differential pressure

 

Differential pressure, burst pressure

 

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