(77e) The Use of Quantitative Risk Assessment to Site Temporary Trailers and Portable Buildings

The American Petroleum Institute (API) developed Recommended Practice (RP) 753 to provide guidance for siting portable buildings in petrochemical processing plants. It identifies analysis methods for siting portable buildings and provides siting distance guidance for vapor cloud explosion hazards.

Minimum safe zone distances established in RP-753 created a dilemma for facilities constrained by space limitations. Appropriate locations to place portable buildings are often difficult to determine. This paper presents a risk-based facility siting analysis approach, which incorporates OSHA requirements and the recommendations of API RP-752 and RP-753 to manage the risks to on-site personnel from explosive, fire and toxic hazards. The paper focuses on analysis of blast explosion hazards and the computation of risk to portable building occupants.

The methods used to define blast locations within a facility are described. Consequence models for specific structure types and windows are developed to determine building damage and occupant casualties. Risk analysis results enable an analyst to specify a safe location for any type of portable building based on acceptable risk criteria. The paper also presents a fully mechanized approach to performing a facility quantitative risk analysis (QRA) for fire, explosion and toxic hazards.