Hazardous Area Classsification
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Objective
Equipment used in hazardous area (where flammable vapor and explosive dusts occur) need to have greater levels of protection against ingress of dust and vapors so that they do not become a source of ignition for such materials.
Since the occurrence of coal dust is inevitable at places where large amounts of coal is handled, the review of electrical systems for their fitness for use in such hazardous area cannot be overlooked
Scope
The following scope is to carry out a HAC design and study which includes drawing on the existing CAD drawing of the proposed plant with respect to the process & storage and preparation of HAC zoning & selection of electrical equipment for each zone drawn along with one site visit.
- Study the process flow and analyzing chemicals with aspect of Hazardous Area classification of the plant with respect to 94/9/EC (ATEX 95), IS 5572, IS 5572, IS 13408 , and relevant NFPA-Standards like 496, 497(if & when reference required) etc.
- To draw and classify zones as per above mentioned standards for each blocks (as per CAD drawing provided)
- To classify the type & selection of electrical equipment to be installed in the Hazardous area as per zones classified.
- To submit the drawings (updated with HAC zones) and equipment selection criteria containing the observations and recommendations.
- To provide the maintenance guidelines pertaining to Electrostatic charges, Flameproof equipment etc.
- Describe loading and unloading practices of chemicals in use.
Indian Context -Standards Followed
Volatile Liquids -
| S.NO. | CODE | TITLE/VERSION ,ORIGIN and predecessor |
| 1 | IEC 60079-10 | Electrical Equipment to be Used in Hazardous Area Containing Flammable Liquids & Vapors. |
| 2 | IS 5572 | Classification of hazardous areas having flammable gases and vapors for electrical installation |
| 3 | IS 5571 | Guide for selection of equipment for hazardous areas |
| 4 | IS 13408 | Code of practice for the selection, Installation and maintenance of Electrical apparatus for use in Potentially explosive atmospheres |
| 5 | NFPA 497b | Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas. |
| 6 | IS 2148 | Electrical Apparatus For Explosive Gas Atmospheres - Flameproof Enclosures "d" |
| 7 | IS 5780 | Intrinsically safe electrical apparatus and circuits |
| 8 | IS 6381 | Construction and testing of electrical apparatus for electrical equipment with type of protection ‘e’ |
| 9 | IS 7389 PART 1 | Pressurized enclosures of electrical apparatus for use in electrical apparatus for use in explosive atmospheres |
| 10 | IS 8289 | Electrical equipment with type of protection ‘n’ |
Dusts-
| S.NO. | CODE | TITLE/VERSION ,ORIGIN and predecessor |
| 1 | NFPA 499 | Recommended Practice for the Classification of Combustible Dusts and of Hazardous Copyright NFPA (Classified) Locations for Electrical Installations in Chemical process areas |
| 2 | IS 15142 | Guide to the use of Electrical apparatus for potentially explosive atmospheres |
| 3 | IS 14154 part 2 | Electrical apparatus with protection by enclosures for use in the presence of combustible dusts. Guide to selection, installation and maintenance |
| 4 | IS 5571 | Guide for selection of equipment for hazardous areas |
| 5 | IS 61241-10 (IEC) | Electrical apparatus for use in the presence of combustible dusts- Classification of areas where combustible dusts are present ( Supersedes IS 13408) |
| 6 | IS 61241-14 (IEC) | Electrical apparatus for use in the presence of combustible dusts- Selection and Installation (supersedes IS 13408) |
| 7 | IS 5780 | Intrinsically safe electrical apparatus and circuits |
| 8 | IS 6381 | Construction and testing of electrical apparatus for electrical equipment with type of protection ‘e’ |
| 9 | IS 7389 PART 1 | Pressurized enclosures of electrical apparatus for use in electrical apparatus for use in explosive atmospheres |
| 10 | NFPA 499 | Recommended Practice for the Classification of Combustible Dusts and of Hazardous Copyright NFPA (Classified) Locations for Electrical Installations in Chemical process areas |
Annexure -1
Indian Rules (Only for reference)
Indian Electricity Rules (IER) 1956 & latest amendment -
Rule No. 51 (1-d) –
In case of installations provided in premises where inflammable materials including gases and /or chemicals are produced, handled or stored, the electrical installations, equipment and apparatus shall comply with the requirements of flame proof, dust tight, totally enclosed or any other suitable type of electrical fittings depending upon the hazardous zones as per the relevant Indian Standard Specification.
Central Electrical Authority (CEA) Regulations 2010 (same as IER)
Regulation No. 37 (iv) –
In case of installations provided in premises where inflammable materials including gases and /or chemicals are produced, handled or stored, the electrical installations, equipment and apparatus shall comply with the requirements of flame proof, dust tight, totally enclosed or any other suitable type of electrical fittings depending upon the hazardous zones as per the relevant Indian Standard Specification.