API RP 752:2009 pdf download
API RP 752:2009 pdf download.Management of Hazards Associated with Location of Process Plant Permanent Buildings.
5.4 Existing Buildings
5.4.1 Building Siting Evaluation for Existing Buildings
Owners/operators shall carry out building siting evaluations for existing buildings intended for occupancy in accordance with Section 6, Section 7, and Section 8.
5.4.2 Mitigation Plan for Existing Buildings
Owners/operators shall develop a prioritized list of all buildings intended for occupancy that fail to meet the building siting evaluation criteria (see 5.3). The basis for the prioritization may include, but is not limited to:
— combination of building damage and building occupancy;
— mitigation measures that can be implemented more quickly than others such as:
— relocation of personnel (especially those who are not categorized as essential personnel),
— provision of blast resistant modular buildings,
— window hazard mitigation;
— risk.
Owners/operators shall develop and implement a mitigation plan and an associated schedule to address all existing buildings requiring mitigation. This plan may include measures described in 5.4.3. The building mitigations may be phased-in consistent with other relative risk mitigation efforts.
5.4.3 Hierarchy of Mitigation Measures
Each building’s potential exposure to explosion, fire, or toxic material release is unique. Table 1 provides examples of possible options to consider in the mitigation plan to reduce the consequence or frequency of scenarios. The list of measures shown in Table I is not all inclusive.
Owners/operators may elect to implement measures that reduce the consequence and/or frequency of scenarios.
Measures are listed in order of decreasing reliability (passive, active, or procedural) and categorized by type
(eliminate, prevent, control, and mitigate). When selecting a mitigation measure it is important to evaluate how
effective the measure will be in reducing the consequence or the frequency of the scenario.
Protection of building occupants requires a balanced approach between passive, active, and procedural measures. Owners and operators should be cautious when relying upon active and procedural measures in mitigation for vapor cloud explosions (VCEs) because time between the initial release of flammable material and the VCE may be insufficient for these measures to be effective.
5.5 Design of New Buildings or Modifications to Existing Buildings
Owners/operators shall carry out building siting evaluations for new buildings intended for occupancy in accordance with Section 6, Section 7, and Section 8.
Owners/operators shall design new buildings intended for occupancy, modifications to buildings intended for occupancy, and building additions intended for occupancy to meet the building siting evaluation criteria.
6.2.1 General
VCEs are typically the dominant explosion scenarios for refineries and petrochemical plants. Other explosion types may dominate at some facilities. The following sections describe the building siting evaluation process for external VCEs. A similar approach may be used for other explosion hazards, such as:
— internal VCEs, such as inside enclosed process units or other enclosures;
— condensed phase chemical explosions;
— dust explosions;
— pressure vessel bursts (PVBs);
— reactive chemical explosions;
— boiling liquid expanding vapor explosion (BLEVE).
See the fire and explosion section in the bibliography for additional information on other types of explosions.
6.2.2 Factors Influencing the Potential for VCEs
The five conditions necessary for VCEs to occur are:
— release of flammable material,
— sufficient mixing with air to produce a flammable mixture,
— delay which allows the flammable cloud to grow,
— ignition of the dispersed vapor cloud, and
— congestion with or without confinement to accelerate the flame front.
Releases of flammable liquids and gases have the potential to form a flammable vapor cloud. Under elevated process temperatures or pressures, releases of combustible liquids can also result in a flammable cloud.
Parameters such as pressure, temperature, weather conditions, ignition timing, discharge area, location, and orientation of the release affect the size of a vapor cloud.
Although processes may handle materials with the potential to generate a flammable vapor cloud, only some areas of the site may have conditions suitable for a VCE to occur. The main conditions that can determine whether a VCE will occur are the degree of congestion and degree of confinement. The congested and confined region may be the process area which is the source of the flammable material, or a nearby process area or even a congested/confined area containing equipment in nonhazardous service. Inherent properties of the material such as flammability range, vaporization and dispersion properties, and flame propagation properties affect the severity of a VCE.
