Electrical equipment isolation

Storage tanks should be designed in accordance with the ASME code for unfited pressure vessels. AH-welded constmction is recommended. Ethylene oxide storage tanks should be electrically grounded, isolated from potential fire hazards, and equipped with pressure rehef devices. New equipment should be cleaned of iron oxide and immediately purged with inert gas. 

Introduction of non-flameproof electrical equipment into restricted area Mechanical isolation, e.g. conveyors, lifts Confined space entry Radioactive areas... 

Checking the starter before working on electric equipment is a useful final check that should always be made, but it does not prove that the equipment has been isolated there may be an interruption in the power supply. 

All electrical systems must be provided with protection equipment, the purpose of which is to isolate faulty electrical equipment from the electrical supply system as rapidly as possible. This can be achieved by use of devices which respond directly to the current flowing (e.g. fuses), or by protective relays which respond to fault current flow and are used to initiate the tripping of other devices (e.g. circuit breakers). 

The hazards which stray currents present to electric blasting caps can be greatly diminished by isolating all electric power lines from ground except at the power source and providing a separate, common bus, bonded to the frames of all electrical equipment. 

Once the purchased equipment costs are known, the capital investment can be calculated by summing these results and using ratio factors for installation, piping, buildings, instrumentation, electric equipment, thermal isolation, indirect expenses, etc. (Chauvel, 2000). 

The shock protection by these sources can be implemented in the following ways enhanced insulation of wires and equipment, and insulation of a person who is working on a power line. Electrical equipment can be isolated. These should be properly marked by warning signs of high voltage and electrical shock. 

Another option for isolating electrical equipment from a hazardous atmosphere is an explosion-proof enclosure. An explosion-proof enclosure is a metal container with a flanged or threaded edge with tight tolerances, that is bolted together. An explosion-proof box does not prevent an explosion from occurring... 

The control unit can also be isolated from the hazardous area with an appropriate barrier according to code. To understand the appropriate placement of electronic and electrical equipment in hazardous locations, review The NFPA s National Electrical Code, referred to as NFPA 70. Articles 500-516 are particularly relevant. 

Check electrical equipment regularly for sparks or arcing. These conditions can trigger spontaneous combustion of flammable gases or cause dust explosions. To prevent electrical equipment from contributing to fires (1) Conduct regular inspections of insulation resistance and monitor the quality of insulation layers. (2) Inspect and correct naked wires and metal contacts to prevent short circuit. (3) Install explosion-proof seals or isolated lighting fixtures, switches and protective devices. 

The function of electrical insulation is to isolate conductors of different electrical potential from one another. This potential difference is commonly expressed in volts the greater the voltage difference, the greater the stress on the electrical insulation. Because conductors carry the currents that make electrical equipment work, the tendency is to pack as many of them as possible in the available space. Consequently, electrical insulation is only allotted a small fraction of the total volume of a device, and thus high demands are put on small amounts of insulating material that is frequently present in rather vulnerable shapes, for example, thin coatings and films. 

Wet or damp environments Water can be a good conductor of electricity, hence working with electrical equipment in a wet environment can be a hazardous activity. Electrical equipment should be isolated from moisture. Electrical receptacles in wet or damp environments must be designed for this type of environment, with ground-fault-circuit-interrupter (GFCI) protection. This type of receptacle should be tested periodically in accordance with the manufacturer s recommendations. 

The steering committee should provide guidance as to how unused or abandoned equipment is to be analyzed. An unused storage tank, e.g., may have been declared as abandoned. Yet, if that tank can be filled with process liquids merely by opening valves, then it is not really abandoned, and so it has to be included in the analysis. True abandonment of equipment only occurs when the equipment (including all associated instrumentation and electrical equipment) is positively isolated and/ or disconnected. 

Hazardous areas (for electrical equipment and other ignition sources) Emergency (ESD, subsea isolation valve, fire and gas, evacuation) Vents Flares Ventilation Effluents Drains... 

B. Mains Disconnect Switches Mains disconnect switches are required on all machines to isolate the entire electrical equipment. The OFF position must be lockable, lEC symbols for ON/OFF positions must be present and meet the relevant EU standards for construction and operation, which is assured if the device... 

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