Filtre Teknolojisi

Duman Testi 1822-4

  • The leak test serves to verify that filter elements have no leaks which mean local penetration values above the permissible limits (see EN 1822-1, table 1). The Oil Thread Leak Test may be carried out as an alternative leak test method for filters of group H (classes H13 and H14). The reference for this leak test is however the particle count scan method as described in the body of this standard. The Oil Thread Leak Test is also acceptable as a test procedure for filter shapes for which the scan method cannot be applied (e.g. filter elements with Vbank media panels or for cylindrical filters).

    The Oil Thread Leak Test is a qualitative test method where the absence of leaks is demonstrated visually. Therefore, it is essential to carry out regular training of the test personnel and to verify the sensitivity of the procedure and the method at regular intervals by using reference filter elements with well defined leaks, characterized by the reference scan test method. The local penetration of the leaks in the reference filter elements shall be between the limit values for the filter class defined in EN 1822-1, table 1 and maximum double the corresponding limit value. In the test set-up the filter shall be subjected to a flow of a polydisperse oil-drop aerosol with a speed of approximately 1.3 cm/s (42 m3/m2/h), which may be varied to optimize the procedure. The filter shall be placed horizontally on a diffuser or box. The test filter mounting assembly shall ensure that the test filter can be sealed and subjected to the flow in accordance with the requirements. It shall not obstruct any part of the filter cross sectional area.

    The polydisperse test aerosol shall be generated by nebulising from a liquid aerosol substance in accordance with para. 4.1 of EN 1822-2. The median value of the particle diameter shall lie between 0.3 and 1.0 μm. The mass concentration shall be 1.5 g/m3 (determined by gravimetric methods).

    The downstream side of the filter shall be illuminated from vertically above with a white (³ 4000 K) fluorescent lamp or halogen lamps. The brightness of the lamp shall be > 1000 Lux at the working plane. The surroundings of the filter shall be darkened, and the observational background shall be black. Uncontrolled air currents from the surroundings shall be screened out.

    Under these conditions, leaks can be recognized in from of a clearly visible oil thread which appears due to the leakage. If no oil threads can be seen the filter up to class H14 is free from leaks as per the leak limit values defined in EN 1822-1, table 1.

    The position and the brightness of the lamp may be adapted to the examiner’s subjection perception by using reference filter elements with well-defined leaks characterized by the scan test method. It is also recommended that reference filters are used with well defined leaks in the medium, in the frame corners and in the medium, close to the sealant.

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