In industries such as electronic manufacturing, petrochemicals, and pharmaceutical production that are sensitive to static electricity, electrostatic discharge may cause serious accidents such as equipment failure, product damage, and even fire and explosion. As an important equipment for foot protection of workers, safety shoes have a direct impact on the safety of the working environment and the stability of production due to their anti-static performance. Therefore, conducting scientific and standardized anti-static testing on safety shoes has become a key link in ensuring industry safety production. This article will comprehensively analyze the anti-static testing technology for safety shoes from the aspects of testing principles, equipment and methods, technical indicators, and precautions.
1、 The core principle of anti-static testing for safety shoes
The anti-static function of safety shoes mainly relies on the addition of materials to the sole of the shoeThe addition of conductive and anti-static components is achieved. These components can construct charge conduction channels, allowing static electricity generated by workers during walking to be conducted to the ground through the sole of the shoe, thereby avoiding the accumulation of static electricity on the human body or clothing. The core principle of anti-static testing is to simulate actual work scenarios, measure the resistance value or charge dissipation time of safety shoes under specific conditions, and determine whether they have effective electrostatic conductivity and meet relevant safety standards.
From an electrical perspective, when the human body comes into contact with safety shoes and is in a walking state, the static electricity generated by the human body will be transmitted to the sole of the safety shoes through the feet. If the anti-static performance of the sole is qualified, static electricity will quickly flow to the ground along the conductive path of the sole. At this time, the measured resistance value of the sole will be within a reasonable range, and the charge can also dissipate within the specified time; On the contrary, if the conductive components of the sole are insufficient, unevenly distributed, or have aging issues, the resistance value will be too high, and static electricity cannot be conducted in a timely manner, resulting in the risk of static electricity accumulation.
2、 Common testing equipment and testing methods
（1） Core testing equipment
The commonly used equipment for anti-static testing of safety shoes mainly includesAnti static shoe resistance tester、And auxiliary equipment (such as standard test flooring, standard test foot molds, temperature and humidity control devices, etc.).
Anti static shoe resistance testerThis is the most fundamental and widely applicableA general device mainly used to measure the resistance value of the sole of safety shoes.
（2） Testing method
At present, the commonly used anti-static testing methods for safety shoes at home and abroad are mainly based on international standards (such as ISO 20344) and national standards (such as GB/T 20991). The core testing methods includeResistance testing method
Resistance testing method：
Wear safety shoes on the standard test foot mold, connect the foot mold to the positive pole of the test circuit, connect the standard test floor to the negative pole of the circuit, and apply a specified pressure (usually 750N ± 50N, simulating the pressure of human body weight on the sole of the shoe) on the foot mold.
Start the resistance tester and apply a certain test voltage (usually 100V or 500V). After the voltage stabilizes, read the resistance value displayed on the tester. According to the standard requirements, the resistance value of the sole of safety shoes should be within106-109ΩIf the resistance value is less than 10 ^ 6 Ω within the range, it indicates that the conductivity of the shoes is too strong and there may be a risk of electric shock; If greater than10⁹If Ω, the anti-static performance is not qualified and static electricity cannot be effectively dissipated.
3、 Key technical indicators and judgment criteria
The key technical indicators for anti-static testing of safety shoes mainly includeShoe sole resistance value,The requirements for this indicator vary slightly among standards in different countries and regions, but the core scope is basically the same. Taking China's GB/T 20991-2021 "Personal Protective Equipment Footwear" and the international standard ISO 20344:2011 as examples for explanation.
（1） Shoe sole resistance value
qualified rangeAccording to GB/T 20991-2021 and ISO 20344:2011, the resistance value of the sole of safety shoes must meet the requirements10⁶≤ R ≤109ΩThe setting of this range ensures that the shoes have sufficient electrostatic conductivity to dissipate static electricity in a timely manner, while avoiding the risk of electric shock caused by low resistance values (if the resistance value is too low, when the operator comes into contact with live equipment, the current will quickly flow through the shoes to the ground, which may cause electric shock injuries).
Judgment rulesIn the resistance test, if the resistance value of a single test is within the qualified range, the resistance test item of the sample is qualified; If the resistance value exceeds the qualified range twice or more in three consecutive tests, the anti-static performance of the safety shoe is judged to be unqualified and needs to be reworked or scrapped.
4、 Precautions during the testing process
The accuracy of anti-static testing for safety shoes not only depends on advanced equipment and scientific methods, but is also closely related to the operating standards during the testing process. The following are some key precautions:
（1） Sample pretreatment needs to be standardized
Before testing, safety shoes must be placed in a standard temperature and humidity environment (23 ℃± 2 ℃, relative humidity 45% -55%) for at least 24 hours. If the shoe material is hygroscopic (such as leather), the placement time needs to be extended to 48 hours. This is because the moisture content of the shoe material directly affects its resistance value. If the sample is not fully adapted to the environment, the resistance value will fluctuate with changes in moisture during testing, resulting in inaccurate results. At the same time, it is necessary to ensure that the surface of the sample is clean and free of impurities such as dust and oil stains, which may form an insulation layer on the sole of the shoe, hinder static electricity conduction, and affect the test results.
(II)Environmental factors need to be controlled
The temperature and humidity of the testing environment are important factors that affect the test results. In addition to controlling the temperature and humidity during the sample pretreatment stage, it is also necessary to maintain the stability of the environmental temperature and humidity during the testing process, and the fluctuation range should not exceed the standard requirements (temperature ± 2 ℃, relative humidity ± 5%). At the same time, the testing environment should be kept away from interference sources such as strong electromagnetic fields and high-voltage equipment, as strong electromagnetic fields may affect the normal operation of resistance testers and charge sensors, resulting in data distortion; High voltage equipment may generate stray currents, interfere with testing circuits, and affect measurement accuracy.
（3） Equipment calibration needs to be conducted regularly
The testing equipment needs to be regularly (usually every six months or one year) sent to a professional organization for calibration to ensure that the accuracy of the equipment meets the standard requirements. The resistance range and voltage output accuracy of the resistance tester need to be verified through calibration. If the equipment is not calibrated on time, measurement deviation may occur, resulting in qualified samples being misjudged as unqualified or unqualified samples being misjudged as qualified, posing a hidden danger to safety production.