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Assignment of Aperture Numbers (Example)
Blau-Metall issues Inspection Certificates 3.1 for test sieves with perforated plates featuring round apertures in accordance with the requirements of the international norm ISO 3310-2. Exceeding the requirements of the standard, our inspection protocols show all parameters determined during optical inspection instead of listing only the number of measured apertures and their mean widths. The number of inspected apertures complies or exceeds the requirements of the standard.

For every Blau-Metall sieve manufactured according to ISO 3310-2, we complete a certification inspection and save the inspection protocol in our records for at least one year. Customers can therefore request Inspection Certificates 3.1 for at least one year after receiving the product, without having to send the sieves back to us for measurements. Inspection according to Calibration guidelines, including at least three times the number of apertures required for certification, can be carried out at the request of the customer.

Assignment of aperture numbers: As outlined in ISO 3310-2, the optical inspection is carried out along two straight lines running in different directions, each at least 150 mm in length, whereas every line includes at least eight apertures for measurement. Requirements of older version of ISO 3310-2 with respect to the angle between the two lines are being followed as closely as possible within the geometry of the given perforation pattern. The assignment of aperture numbers occurs sequentially starting from top left to bottom right followed by the second line that is numbered from top right to bottom left with the sieve label acting as reference (pointing down in the image to the right). This allows the same lines to be inspected for re-certification so that a direct comparison is possible. For Sieve Calibration, additional lines may be inspected which will be numbered accordingly.

Nomenclature & Translation of Inspection Certificate:

Aperture Width / Diameter (Lochweite / Durchmesser): Shown in the protocol are the diameters w for every inspected aperture (Desired Value (Sollwert) corresponds to the Nominal Aperture Width, the upper- (Obergr.) and lower (Untergr.) limits correspond to the permissible variation of aperture size, ref. ISO 3310-2 Table 1 Column 4)

Pitch (Teilung): Distance between the centers of two adjacent apertures (Desired value corresponds to Preferred Pitch pnom, the upper- (Obergr.) and lower (Untergr.) limits correspond to the Parameters pmax and pmin of the permissible range for the aperture pitch, ref. ISO 3310-2 Table 1 Columnds 5-7)