API RP 752 Compliance

The following is a brief description our protocol for complying with API Recommended Practice 752, “Management of Hazards Associated With Location of Process Plant Buildings.” The protocol is divided into four phases, although it will not be necessary to conduct all four phases for each building. At the completion of each phase, the analysis can be stopped if the results of the analysis up to that point indicate the risk to occupants of the building is within the acceptable range. This protocol is similar to our protocol for complying with API Recommended Practice 753, “Management of Hazards Associated with Location of Process Plant Portable Buildings.”

Phase 1 – Determine if Analysis is Warranted

Based on site-specific factors and company policies or criteria, there may be no need to conduct a consequence or risk analysis for a given building at a specific facility. Some of the factors that should be considered when making this judgment are listed below:

  • Process Materials
    • Volatility
    • Flammability/Explosibility
    • Toxicity
    • Operating conditions (pressure and temperature)
    • Chemical reactions
    • Inventories
    • Flow rates
  • Control Building
    • Location (relative to potential accident sources)
    • Ventilation (pressurized versus non-pressurized)
    • Construction/Blast-resistance
    • Criticality of building usage
  • Occupancy
    • Maximum and average number of occupants
    • Average personnel hours of occupancy per week
    • Criticality of personnel functions
  • Company-Specified Criteria
    • Minimum spacing distances
    • Level of blast resistance required at minimum spacing
    • Minimum occupancy rate of concern
    • Acceptable risk to control room occupants

If there is a need to analyze one or more buildings, proceed to Phase 2.

Phase 2 – Worst Case Consequence Analysis

Predict hazard footprints for worst case releases (e.g., full-bore pipe ruptures). The hazards of interest may include:

  • Infiltration of toxic gas cloud
  • Infiltration of flammable gas cloud
  • Exposure to blast wave (explosion overpressure)
  • Impact of missiles that result from explosions
  • Exposure to radiant heat

Determine if one or more of these hazard footprints could reach the building in question—at a hazard level capable of severely impacting occupants of the building.

  1. No: Analysis complete.
  2. Yes: Proceed to Phase 3.

Phase 3 – Qualitative Risk Analysis

Predict hazard footprints for credible events (i.e., events that are expected to occur more often than worst case events, but with less severe consequences). This analysis would be limited to the consequences of releases of a given “size” (e.g., releases from one-inch or two-inch holes in pipes and vessels). The “size” of events to be included in this phase would need to be agreed upon by the client.

Determine if one or more of these hazard footprints could reach the building in question—at a hazard level capable of severely impacting occupants of the building.

  1. No: Estimate the probability of events in excess of the “size” analyzed in Phase 3. Combine this with the results of Phase 2 and factors such as occupancy level, criticality, building design, etc., to make a qualitative determination of the risk and its acceptability.
    1. Acceptable: Analysis complete.
    2. Unacceptable: Provide mitigation or proceed to Phase 4.
  2. Yes: Provide mitigation or proceed to Phase 4.

Phase 4 – Quantitative Risk Analysis

Predict hazard footprints for the full range of event sizes.

Estimate the probability of occurrence of each hazard footprint that could reach the building in question—–at a hazard level capable of severely impacting occupants of the building.

Combine consequences and probabilities to estimate the risk.

Assess the acceptability of the risk (i.e., is the risk below the level specified as acceptable by the client?).

  1. Acceptable: Analysis complete.
  2. Unacceptable: Provide mitigation. Repeat Phase 4.

Visual Model of Compliance Process

API RP 752 Flowchart

API RP 752 Flowchart