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B: Arrangement [Table of Contents] D: Equipment and Cables in Hazardous Areas

DNV-OS-A101 Safety Principles and Arrangements

[-] Sec.7: Special Provisions for Production and Storage Units
[-] C: Hazardous Area Classification

Sec.7
C. Hazardous Area Classification

Sec.7
C 100   General

Sec.7 C
101   These requirements are supplementary to general requirements given in Sec.4.

Sec.7
C 200   Product storage tank areas

Sec.7 C
201   The hazardous area classification of product storage tank areas shall follow a recognised code, ref. Sec.4 Table A1.

Sec.7 C
202   Pipe tunnels carrying hydrocarbons or with a common boundary with product storage tanks shall be classified as Zone 1.

Sec.7 C
203   Gas venting systems connected to cargo tanks will give rise to hazardous area, and the zone number shall be based on consideration of the frequency of release. In general, the following principles shall apply:
—the tank venting system used during loading or unloading shall be classified according to a recognised code, ref. Sec.4 Table A1
—the venting system used for thermal breathing (small capacity pressure or vacuum valves) is the source of a spherical hazardous Zone 1 with a radius of 5 m
—for unconventional designs, the extent of hazardous areas from cargo tank vent systems shall be based on the boundaries of 50% LEL concentration.
B: Arrangement [Table of Contents] D: Equipment and Cables in Hazardous Areas