About the principle and test method of safety shoes anti-static tester

Test Instrument

When a (100 ± 2) V DC voltage is applied, the resistance can be measured with an accuracy of ±2.5%. This ensures reliable and consistent readings during testing.

Internal Electrode

The internal electrode consists of stainless steel beads with a total mass of 4 kg and a diameter of 5 mm. To maintain optimal electrical conductivity, it is essential to take measures to prevent or remove oxidation from both the steel balls and the copper plates. Oxidation can significantly affect the performance and reliability of the test results.

External Electrode

The external electrode is made up of a copper contact plate, which should be cleaned with ethanol before each use to ensure a clean and conductive surface for accurate measurements.

Device for Measuring Conductive Coating Resistance

This device comprises three conductive metal probes. Each probe has a radius of (3 ± 0.2) mm and is mounted on a base plate. Two of the probes are spaced (45 ± 2) mm apart and connected by a metal strip. The third probe is positioned (180 ± 5) mm away from the midpoint of the other two probes and is insulated from them to avoid interference during measurement.

Sample Preparation

If the shoe is equipped with an activity mat, it should remain in place during the test. The sole surface must be cleaned with alcohol to remove any release agents, followed by rinsing with distilled water. After cleaning, the sample should be dried at (23 ± 2)°C. It is important not to rub or wear the sole surface, and no organic materials that could damage or expand the sole should be used during the process.

Special Preparation for Wet Conditioning

For specimens tested under wet conditions, a conductive coating of 200 mm x 50 mm should be applied to the sole, covering both the heel and forefoot areas. The dry measuring resistance of the coated surface must be less than 1 x 10³ megohms. The shoe is then filled with clean steel balls and placed on the device’s metal probes, ensuring the forefoot area is supported by two probes spaced 45 mm apart, while the heel area is supported by the third probe. The resistance between the third probe and the others is measured using the test instrument.

According to the function of the tested shoe, the prepared sample should be adjusted according to one of the following conditions:

1) Dry Conditions: (20 ± 2)°C, relative humidity (30 ± 5)% — samples should be conditioned for 7 days.

2) Wet Conditions: (20 ± 2)°C, relative humidity (85 ± 5)% — samples should also be conditioned for 7 days.

If the test cannot be conducted in a controlled environment, it must be completed within 5 minutes after the sample is removed from the conditioning environment.

Test Procedure

Fill the sample with clean steel balls totaling 4 kg. If necessary, use insulating material to raise the upper part of the shoe. Place the filled sample on a copper plate and apply a (100 ± 2) V DC test voltage between the steel plate and the steel balls for 1 minute. Record and calculate the resistance value.

The energy consumption of the safety shoe's sole should not exceed 3 W. If the withstand voltage is reduced due to this 3 W limit, the actual voltage value should be clearly noted in the test report.

China Labor Insurance Network