(49b) What to Consider When Constructing Buildings in Classified Areas

Stuart Powell, Murtaza Gandhi, David Wechsler

Baker Engineering and Risk Consultants, Inc.

Houston, TX

SPowell@BakerRisk.com

Hazardous area classification (HAC) analyses have been a part of hazard mitigation practices across facilities that process flammable and combustible material for many years. In the United States, OSHA mandates that a HAC analysis be performed for such facilities, with the intent of identifying areas where such materials may be present and helping to control potential ignition sources in the area. Guidance is provided through documents such as the NFPA 497 standard and API RP 500 to aid operating companies in the development of classified areas to ensure appropriate equipment is selected for the hazardous environment in which the equipment is to be installed.

For operating companies with existing buildings or new buildings that are/will be located within known classified areas, there are specific considerations that must be taken into account such that the equipment and electricals on the interior and/or exterior of the building are properly rated and applicable for the area. In addition, there are protection techniques that can be utilized to help reduce the likelihood of flammable/combustible material accessing the building, such as pressurization and/or automatic detection devices that can de-energize equipment in the building upon gas detection, as detailed in NFPA 496. These considerations and protection techniques ultimately seek to control the ignition source potential of the equipment associated with the building.

For buildings that contain internal sources of flammable or combustible materials such that the interior of the building is rated as a classified area, additional considerations apply. Topics such as adequate ventilation, periodic testing of gas detection with activation of increased ventilation, deenergizing of equipment in the building, and whether the classified area extends beyond the confines of the building wall to the surrounding area, are but a few of the necessary considerations.

This paper addresses considerations for operating and design companies regarding ignition controls that are introduced when locating buildings in classified areas. Guidance from NFPA 497, API 500, and NFPA 496 will be reviewed, discussed, and summarized. Distinction will be made between buildings that house internal releases of flammable/combustible material and those that do not.

Key words:

Hazardous Area Classification, Electrical Hazardous Area Classification, Buildings in Classified Areas