BS EN ISO 2746:2015 pdf free
BS EN ISO 2746:2015 pdf free.Vitreous and porcelain enamels – High voltage test
Pulsed DC-voltage generator, conforming to the requirements of IEC/TS 60479-2 able to deliver a DC-voltage corresponding to the testing voltage. The voltage shall be adjustable and measurable at the test probe with limiting deviations +20 %/-10 % for test voltage greater than 10 kV and limiting deviations +40 %/-10 % for test voltages less than 10 kV.
Test electrode, made out of metal wire or conductive rubber that is unaffected by a spark discharge.
NOTE Alternative test electrodes can be used providing they are unaffected by a spark discharge.
Insulated hand-piece, provided externally with an earthed cover for DC-voltage and pulsed DC-voltage devices. Pulsed DC-voltage generators can produce an electric shock to users because of capacitive coupling between cable and hand-piece during operation.
Brush holder, of metal wire (used for the test brush), constructed such that it is completely unaffected by the spark discharge and covers as large an area as possible when sweeping the enamel surface.
For a correct determination of these defects, the appropriate test voltage shall be used. This voltage depends on the length of the defect gap, which corresponds to the thickness of the enamel layer. Too low a voltage will not result in the determination of all defects. Too high a voltage will result in a breakdown of thin residual enamel layers (destructive testing). In order to look for defects which extend down to the metal base (e.g. open pores), the test voltage shall be as follows:
– DC-voltages shall be set to the values given in Table 1.
Other voltages may be chosen by mutual agreement between interested parties.
– voltage of pulsed DC-voltage generators shall be agreed between the interested parties.
Table 1 shows the minimum voltage needed to arc through a defect which is open to both the surface and the metal substrate. Note that the dielectric breakdown of air is based on measurement at 23 °C and 60 % maximum relative humidity.BS EN ISO 2746 pdf download.
