In many industries the risk of developing an explosive atmosphere is present. Examples of this are natural gas leakages and spillage of volatile hydrocarbons. These situations can, if an ignition source is present, result in an explosion. In order to prevent ignition sources there are several requirements for equipment intended for use in such atmospheres.
The ATEX directive requires equipment intended for use in explosive atmospheres to comply with relevant standards. For mechanical equipment without electric components this standard is EN 13463-1. Several requirements are listed in this standard – among them the requirement to prevent electrostatic discharges. Electrostatic discharges and electrostatic sparks are, if the right conditions occur, very potent ignition sources. Therefore, several tests on the material properties have been developed in order to determine whether the material can be safely used without introducing an ignition source. Gexcon have the staff and equipment to perform tests in order to determine the electrostatic properties of the materials, and can also provide clients with advice on electrostatic matters.
Description of Tests Performed
On the basis of the actual state of the application one of the following tests can be used:
EN 13463-1, Annex D: This test assesses the ability of a material to accumulate and hold electrostatic charge. In short, this test procedure consists of manually rubbing the material and measuring the resulting discharge. The sample is also charged using a high voltage source. If the recorded value is above a certain threshold the material cannot be used in explosive atmospheres. This test can only be used if the actual charging source is equally strong or weaker than manual rubbing of the material.
IEC 61340-2-3: This test assesses the ability of a material to hold an electrostatic charge. The apparatus used in this test is an electrode pair, a DC voltage source and an ammeter. 100 volts are applied on the electrode pair situated on the specimen and the resulting current is measured using the ammeter. If the current is above a certain limit the material is considered safe to use, even if the charging source is stronger than manual rubbing, provided that the material is properly grounded.
EN 13463-1: If the breakdown voltage of a material is lower than a certain value the material can be used safely. This breakdown voltage can be determined by tests at Gexcon.