Electrostatic Charge Transfer Measurement
Electrostatic charge transfer refers to the movement or exchange of electric charge between materials or objects through contact or proximity, resulting in the redistribution of charges and potential differences between the surfaces involved. This phenomenon occurs due to the movement of electrons from one surface to another, leading to an imbalance of positive and negative charges. This test is designed to measure the charge transferred in electrostatic discharges from insulating surfaces. The test is best applied to brush discharges from material/ equipment surfaces and provides an alternative to determining discharge energy by ignition of local flammable gas mixtures.
SPARKS FROM ISOLATED CONDUCTORS AND INSULATORS
The use of insulating materials can isolate metal plant components or other conductive objects from earth. By being close to charged material, such conductors can become charged by induction, charge sharing or by collecting sprayed charge or charged particles.
These conductors can acquire a large amount of charge and energy and can store it for a long time. Most of that energy can eventually be released as an incentive spark to earth.
Igniting Power of Insulators
To determine the direct incendivity of discharges, the insulating material is charged under the worst-case conditions as highly as possible (at least to the maximum level that could occur in practice) to provoke discharges to an earthed sphere (ignition probe) approaching and to pass such provoked discharges through gas mixtures of the known MIE value. The test is conducted in accordance with IEC/TS 60079-32-1
Electrostatic Discharge testing
Isolated conductors and insulators can present hazardous conditions in a flammable atmosphere when they are electrostatically charged. This is primarily due to the retention of the charges within or on the surface of the materials. A series of electrostatic discharge testing such as charge transfer, igniting power, sparks from isolated conductors and insulators and charge transfer may be able to provide risk assessment for the use of such materials in a flammable atmosphere.
Testing Principle and Methodology
The test applies to solid insulating materials and not powders. The material to be tested is conditioned at a relative humidity of 25% for at least 24 hours. The test sample is rubbed with a material from the positive end of the triboelectric series. Whilst rubbing at least one stroke per second with medium force (approximately 40 N), in direction away from the test person. Rubbing is continued for (10 ± 1) s and is terminated with a hard rubbing stroke.
The sample is grabbed by using an isolated grip to minimize inadvertent discharge.
The sample is lifted carefully at least 20 cm away from the table losing as little charge as possible.
The sample is discharged as quickly as possible by slowly moving the spherical electrode of the measuring equipment towards the test sample until a discharge occurs. Particular attention is made to discharge the most hazardous parts of the sample, e.g. great surface areas and small conductive items.
Charge Transfer Set up
Applicable Standard
The charge transfer is performed according to IEC 60079-0 and IEC/TS 60079-32-1
Data Interpretation
Results is interpreted according the IEC 60079 standard table below providing classification of explosion groups of materials.
According to IEC 60079-0 and IEC/TS 60079-32-1, the maximum allowed surface area of insulating materials is limited in explosive atmospheres. However, there are many cases where a sufficient safety level is still achieved with insulating materials. These cases include surfaces with embedded corona tips, enclosures backed with printed boards as well as materials with an internal breakthrough voltage of only a few kilovolts. By knowing the maximum charge that can be transferred from an insulating material, the maximum allowed surface area can be determined to handle the material safely in an explosive atmosphere.
When to perform Charge Transfer Measurements Â
The electrostatic charge transfer test is recommended in scenarios where the generation and transfer of static electricity can pose risks or interfere with the safe handling, manufacturing, storage, or transportation of materials. Charge transfer measurement is recommended for all insulating solid materials with high charge relaxation times where proper earthing is not practical to achieve.
Why work with Prime Process Safety CenterÂ
- Prime Process Safety Center is a leader in process safety testing with very experienced laboratory personnel. At Prime Process Safety Center our goal is to provide accurate, reliable and defensible data that meets industry and regulatory standards. We understand the need for the quality of your data, and we work assiduously to achieve just that.
- We are knowledgeable and experienced in performing electrostatic charge transfer tests, ensuring accurate and reliable results.
- We have state-of-the-art charge transfer testing equipment, providing precise and sensitive measurements.
- We follow strict testing protocols and quality control measures to ensure consistent and reliable test results.
- Our team can interpret and analyze the data obtained from the tests, providing valuable insights and recommendations for your specific application or research.
FAQs
What is Electrostatic Charge Transfer?
Answer: Electrostatic charge transfer refers to the movement or exchange of static electricity between two materials or surfaces, leading to an imbalance in electrical charges and potentially resulting in sparks or electrostatic discharge.
Why is Electrostatic Charge Transfer Significant?
Answer: Understanding charge transfer is crucial as it can lead to static buildup, which, if discharged in sensitive environments or near flammable substances, may cause sparks, fires, explosions, or damage to electronic components.
How is Electrostatic Charge Transfer Measured or Tested?
Answer: Charge transfer is evaluated through various tests measuring the accumulation or dissipation of static charges on materials or surfaces using specialized instruments.
What Factors Influence Electrostatic Charge Transfer?
Answer: Material composition, surface characteristics, environmental conditions (humidity, temperature), movement, and friction between materials are factors that impact the generation and transfer of static electricity.
What Industries or Applications Require Attention to Electrostatic Charge Transfer?
Answer: Industries involving flammable substances, electronics manufacturing, cleanroom environments, powder handling, chemical processing, and transportation of sensitive goods commonly address electrostatic charge transfer to prevent hazards or damage.