Honeywell - KINGS ESD Flyer

THE ELECTRICAL RESISTANCE TEST

ESD safety shoes are designed to safely discharge static electricity from a person’s body to the ground thanks to conductive materials in their soles that enable electricity to flow through them, rather than building up on the person wearing them. ESD protection in safety shoes is crucial for reasons which include those of protecting sensitive electronics, preventing fires and explosions as well as helping to guarantee workplace safety for all involved employees and quality control on site.

To ensure the highest level of safety in environments where electrostatic discharge can pose a significant risk to workers’ well-being, the EN 61340-4-3 standard provides a comprehensive test method for evaluating ESD shoes. The electrical resistance test is an important evaluation method for safety footwear, helping to assess whether adequate insulation is available to protect the wearer from electrical hazards. To help ensure accurate and reliable results of the investigation, the testing environment must be strictly controlled.

The actual test procedure involves conditioning the shoe in a controlled environment of 20°C (± 2°C) and 30% (± 3%) relative humidity for at least 24 hours. Once conditioned, the shoe is filled with 4kg of stainless-steel balls, each with a 5mm diameter. If the shoe’s upper is not sufficiently tall, insulating materials are used to increase its height. The shoe is then placed on the metal plate, while the steel balls inside are connected to the measurement device.

To achieve the necessary testing conditions, the temperature is maintained at 23°C (± 2°C), while humidity levels are kept within a range of 25% (± 3%). Before testing, the footwear undergoes a conditioning period of at least 48 hours to acclimate to these controlled conditions. The testing setup is also essential to the reliability of its final results. The testing process begins with a meticulous setup, using essential equipment formed of a stainless-steel metal plate for the external electrode and stainless-steel balls as the inner electrode. A precise DC power supply, capable of delivering 100V ± 2V, and a resistance measurement device with grade 2.5 accuracy are also employed. Before the test, the sole of the shoe is cleaned with ethanol, washed with distilled water and then dried under specified conditions. A conductive layer of 180mm x 40mm is then applied to prepare the sample for testing.

A voltage of 100V DC is applied between the inner and outer electrodes for one minute, after which the voltage and current values are recorded. The electrical resistance is calculated using Ohm’s Law, ensuring precise and reliable results.To pass the test, the safety shoe must show resistance values falling within a specific range. The lower limit is set at 1 × 10 ⁵ Ω (0.1 MΩ), while the upper limit is 1 × 10 ⁸ Ω (100 MΩ).Resistance values below the lower limit indicate insufficient insulation, posing a potential electrical hazard to the wearer of the safety shoes in question. Conversely, values exceeding the upper limit may suggest excessive resistance, potentially hindering the proper functioning of certain electronic devices that might be worn with the footwear. Adhering to this rigorous test method guarantees that ESD safety shoes meet the necessary standards for protecting against electrostatic discharge, particularly in industries that handle sensitive electronic components. This meticulous process underscores the importance of safety and reliability in ESD footwear, ensuring protection and peace of mind in the workplace. By adhering to these stringent testing protocols and resistance criteria, the levels of protection and performance of the tested safety footwear can be assessed reliably and objectively. This test method helps to ensure that ESD shoes meet the required standards for electrostatic discharge protection in various work environments, particularly in industries dealing with sensitive electronic components. Thus, it helps to safeguard wearers of safety footwear from electrical hazards, offering complete awareness and peace of mind on the job.