Standard_Parts_Catalogue

Page 1627 | 3.5 Controlling, Venting, Sealing of Liquids and Gases 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 Air permeability volume dependent on differential pressure Differential pressure, burst pressure GN 7404 Two-Way Breathable Membranes continued Membrane structure – Materials The membranes use a non-woven nylon material as a substrate with a comple- tely 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 ma- nufacturing, 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 asses- ses, 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 econo- mically viable methods is 50 µm. Functionality – Service conditions – Installation position 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. Thermal - The membrane enclosure may not be used in temperatures exceeding 100 °C. The membrane itself can resist temperatures of up to 150 °C. Chemical - The membranes are resistant to a wide range of chemical substances frequently used in mechanical and automotive engineering, e.g., oils, fuels, organic solvents, and alcohols. A tolerability test should be per- formed if you have any doubts. Resistances Membrane, microscopic images, 2000x magnification Technical parameters 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 achie- ved and the differential pressure, which should not exceed 1 bar.