Electrical Apparatus For Use Research Articles

Effect of rusting and mechanical damage of gap surfaces on efficiency of flame gaps in flameproof electrical apparatus

Potentially incendiary electrical apparatus for use in the presence of explosive gas atmospheres have to be specially designed to prevent the apparatus from igniting the gas. Flameproof design is one of several options, and one requirement is then that any holes and gaps in the enclosure wall be designed to prevent a gas explosion inside the enclosure from being transmitted to an explosive gas cloud outside it. Current standards (IEC) require that flame gap surfaces have a surface roughness of <6.3μm. Any damaged flame gap surface has to be restored to this quality. The present investigation has demonstrated that flame gap surfaces in flameproof electrical apparatuses can suffer considerable corrosive and mechanical damage without any reduction of gap performance. In some cases very significant mechanical surface damage in fact improves gap performance. Possible physical reasons for this are discussed. These findings indicate that current high costs of repairing and replacing flameproof electrical apparatus in process plants offshore and onshore can be significantly reduced without any increase of explosion risks.

Effects of significant damage of flame gap surfaces in flameproof electrical apparatus on flame gap efficiency

Electrical apparatus for use in the presence of explosive gas atmospheres has to be specially designed to prevent the apparatus from igniting the gas. Flameproof design is one of several options, and one requirement is then that any holes and slits in the enclosure wall be designed to prevent a possible gas explosion inside the enclosure from being transmitted to an explosive gas cloud outside it. Current standards (IEC) require that joint surfaces have a surface roughness of <6.3 μm. Any damaged joint surface has be restored to this quality. The present investigation has demonstrated that flame gap surfaces in flameproof electrical apparatuses can suffer considerable mechanical and corrosive damage before the flame gaps no longer function satisfactorily. In some cases very significant mechanical surface damage in fact improves the gap performance. This indicates that current high costs of repairing and replacing flameproof electrical apparatus in process plants offshore and onshore can be reduced considerably without any increase of the explosion risk.

Selection of electrical equipment for hazardous areas

The new installation standard gives the user not only the possibility to select the electrical apparatus according to the correct types of protection for the zone but also the possibility to make a risk assessment for the correct selection of the apparatus. The insertion of the requirements for electrical apparatus for use in combustible dust is foreseen for the future edition following this edition of IEC Standard 60079-14.

Selection of electrical apparatus for use in explosive gas atmospheres

Proper selection of electrical apparatus is essential for ensuring an adequate level of safety at reasonable costs. This article provides the basic facts for bridging the gap between apparatus construction and installation

An automatic wire-snapping machine for experiments on electrical ignition of gases

Research on the intrinsic safety of electrical apparatus for use in coal mines includes determining the probability of igniting methane by sparks in conditions where this probability is low. As part of a procedure for standardizing the experimental conditions, a spark is made when a wire carrying a current is broken, so that the spark occurs between freshly exposed surfaces. This paper describes a machine that has been constructed to perform automatically the large number of experiments needed.