4 Test setup
4.1 Spark generation circuit
Appendix A lists a number of appropriate circuit forms, all of which should have the following characteristics. The following is only about circuits:
Discharge circuit inductance: 1 mh 2 mh, except when this data is used to assess the electrostatic hazard of the discharge circuit with an inductance not exceeding 25 h
The resistance of the discharge circuit ( ) is as low as possible and does not exceed 5;
Electrode Material;Stainless steel, brass, purple steel or tungsten;
Electrode diameter and shape: 20mm±0.5mm。The use of spherical electrodes reduces the effects of corona on pointed electrodes, which can produce erroneous spark energy values. If a pointed electrode is used, the effects of corona should be carefully considered.
Electrode gap: 6mm (minimum);
Capacitance: low inductance capacitance, inrush current resistance;
Electrode distribution capacitance: as low as possible;
Insulating material between the electrodes: sufficient to stop leakage currents.
Note: In general, the minimum resistance between electrodes required for a minimum ignition energy of 1 mJ is 100000000000 and the minimum resistance required for a minimum ignition energy of 100 mJ.
for 100000000000.
4.2 Test containers
The recommended test vessel is a 20 L spherical container or a Hartman. These containers are described in References [6] and [7]. As long as it meets 62 calibration requirements, other containers can also be used.
5 Test samples
The test should be carried out on a sample established equivalent to the actual conditions of the plant. The minimum ignition energy decreases as the particle size decreases. The test should be performed on the sample material that is consistent with the particle size in actual use, or finer than actually used, or the finest sample.
For comparison tests, samples should be prepared by a fixed method with fixed particle size and moisture content.
Note: If the particle size of the material is unknown, the test should be performed on particles smaller than 63 m in size.
The minimum ignition energy decreases with the decrease of particle size, and it is advisable to check whether the particle size of the sample represents the finest particle material that can appear in the factory, and the test should be carried out on particles with a size of less than 63 m.