Intrinsically safe equipment

Intrinsically Safe Equipment and wiring which is incapable of releasing sufficient electrical or thermal energy under normal or abnormal conditions to cause ignition of a specific hazardous atmospheric mixture or hazardous layer. 

The design of intrinsically safe equipment is governed by the rules of NFPA Publication No. 493, Standard for Intrinsically Safe Apparatus and Associated Apparatus for Use in Class I, II, and III, Division 1, Hazardous Locations. It is cautioned, however, that the design of intrinsical-... 

Zone 0 explosive gas-air mixtures are present continuously or present for long periods. Specify intrinsically safe equipment. 

Specify intrinsically safe equipment, or flame-proof enclosures enclosures with pressurizing and purging. 

Availability. Both Underwriters Labatories and Factory Mutual Research publish yearly guides to electrical equipment which they have certified and continue to certify as being rated for use in hazardous environments. Many of the items contained in these guides are rated as intrinsically safe or as associated equipment for use with intrinsically safe equipment. Further, the amount of equipment available should increase each year as the demand increases for intrinsically safe electrical circuits. 

Bartkus, Albert A., "Intrinsically Safe Equipment For Use in Class I, Division 1 Hazardous Locations", Lab Data, Winter/Spring, 1982... 

Intrinsically-safe equipment is designed to be incapable of releasing electrical or thermal energy that would ignite a hazardous atmospheric mixture. 

Intrinsically safe equipment approved for use in the European community might not pass UL 913 tests for intrinsically safe designation in the U.S. The standards are similar, but not identical. Integration components intended for different codes or systems should be avoided, unless approved by an appropriately qualified electrical engineer. 

Ordinary electrical equipment cannot be installed in zone 0, even when it is flameproof protected. However, many chemical and oil-processing plants are entirely dependent upon instrumentation and data transmission for their safe operation. Therefore, very low-power instrumentation and data-transmission circuits can be used in special circumstances, but the equipment must be intrinsically safe, and used in conjunction with a safety barrier installed outside the hazardous area. Intrinsically safe equipment must be marked Ex ia or Ex s , specially certified for use in zone 0. 

Has a determination been made to use intrinsically safe equipment ... 

In a circuit where the amount of electrical energy available to cause a spark is below that necessary for igniting flammable vapour or gas, the equipment is considered to be intrinsically safe. It is particularly suitable for use in instrumentation, remote control etc. Intrinsically safe equipment to category IA may be used in any Zone except that in which there are contacts that could spark. It should not be used in Zone 0. Category IB equipment may be used in all zones except Zone 0, See BS5958 . ... 

Intrinsically safe. Equipment and associated wiring approved as intrinsically safe is permitted in any hazardous (classified) location in-ciuded in its iisting or iabeiing. 

Intrinsically safe equipment and associated wiring. Equipment and associated wiring in which any sp or thermal effect, produced either normally or in specified fault conditions, is incapable, under certain prescribed test conditions, of causing ignition of a mixture of flammable or combus-... 

Any experienced maintenance organization can coordinate the replacement of conventional electrical equipment with intrinsically safe equipment. 

ISA R12-6 defines IS as A type of protection in which a portion of the electrical system contains only intrinsically safe equipment (apparatus, circuits, and wiring) that is incapable of causing ignition in the surrounding atmosphere (ref Clause 3.12 of ANSI/ISA RP12.06.01 2003)... 

These curves reflect the worst-case scenario. Because of the low power required by today s electronics, most manufacturers of intrinsically safe equipment find it safer (and easier) to start by designing the equipment for the worst-case specifications [24]. 

There are two categories of intrinsically safe equipment recognised in Europe. Type ia must be incapable of causing ignition with two independent faults while type ib must be incapable of causing ignition with a single fault. The former may be used in all Zones while the latter is suitable for use only in Zones 1 and 2. 

Any intrinsically safe equipment will also need to be used by competent persons and included both within an inspection and testing programme undertaken by competent engineers and in a planned preventive maintenance programme. 

LHDC is used in a wide variety of applications but is particularly suited where there is a harsh environmental condition, a physical or hazardous maintenance access constraint to the protected area, and/or a requirement to cost-effective install detection in close proximity to the fire risk. The main benefits of LHDC systems are that they are effective in detecting a rise in temperature at any point along their length, and can be used in environments that may be potentially explosive and therefore require the use of intrinsically safe equipment (see Chapter 8). 

The safety profile PROFlsafe defines the connection of intrinsically safe equipment (emergency stops, immaterial barriers, locks) to programmable controllers on PROFIBUS. The specific area of safety, most of whose constituents were previously connected by wire, may benefit from the multiple strengths of open communication on PROFIBUS. 

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