Explosion-Proof Equipment and Instruments

Permissible Vessel and Surrounding Area Must be Free from Flammable Vapors, Gases, and Liquids 

Charging solids with a nongrounded and conductive chute can result in a buildup of a charge on the chute. This charge can accumulate and finally produce a spark that may ignite a dispersed and flammable dust. 

For solvent-free solids the use of nonconductive containers is permitted. For solids containing flammable solvents, only conductive and grounded containers are recommended.10 

All electrical devices are inherent ignition sources. Special design features are required to prevent the ignition of flammable vapors and dusts. The fire and explosion hazard is directly proportional to the number and type of electrically powered devices in a process area. 

10Expert Commission for Safety in Swiss Chemical Industry, Static Electricity Rules for Plant Safety, Plant/Operations Progress (January 1988), 7(1) 1. 

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Inexpensive, rugged fiber optics, equipped with every type of probes, make all these instruments amenable to processing measurements in real time. Recently, several manufacturers have been introducing wireless units that are smaller, more rugged, and faster than conventional spectrometers. Many process instruments from a decade ago were simply lab instruments fitted with explosion-proof enclosures and placed in factories. They are now being built specifically for the process environment. 

In Division 1 areas, meters, instruments, relays, and similar equipment containing high-temperature or arcing devices must be installed in approved explosion-proof or purged enclosures. Unless such devices are specifically labeled as suitable for Class I, Division 1 areas, it is best to assume they are not suitable. 

Turnkey plant. Consists of all the hardware, software, technical data, and technical assistance necessary for the installation of a complete operating facility for the production of the commodity, a chemical substance, at defined production rates and to specified product qualities. Hardware consists of all the equipment, components, control valves, instruments, reaction vessels, feed lines, and exposition proof barriers necessary for the conduct of the unit operations of the overall production process, whether the items arc assembled or disassembled for transportation. The plant may be designed for installation at a prepared site that includes locally constructed and installed explosion-proof barricades... 

The AMDR is equipped with some instruments that are used to detect the surrounding environment and transfer information back to the control centre. The explosion risk is very high when these instruments and equipments in service. So, we should use the intrinsically safe electrical equipment or other special design for the electrical equipment. In principle, the flame-proof equipment is not allowed to use in mine. But the intrinsically safe electrical equipment is very rarely at present, especially the power supply, motor and other key equipments. Therefore, the AMDR adopted the safety strategy of flame-proof after the redundant safety measures drawn up in the case of the basic principles of electric explosion-proof allowed. 

European directives are an important instrument of the New Approach in the field of technical harmonisation and standardisation. They are intended to remove the technical barriers by harmonising product regulations and conformity evaluations. No specifications but only essential requirements restricted to the protection of health and safety of users and the protection of environment, are laid down in the New Approach directives. Up to 2000 some 20 directives have come into force. The directives cover products where safety aspects are relevant such as lifts, pressure equipment, explosion-proof materials, toys and personal safety equipment. 

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