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Facility siting blast contours

FACILITY SITING

What is facility siting?

Facility Siting is a requirement for all oil, gas and chemical facilities following the Environmental Protection Agency (EPA) RMP rule and Occupational Safety and Health Administration (OSHA) Process Safety Management (PSM) of Highly Hazardous Chemicals standard (29 CFR 1910.119). It falls within the Process Hazard Analysis section of the PSM regulation. 

 

Facility siting involves the assessment of explosion, fire, and toxic hazards on people in occupied buildings in the facility. The American Petroleum Institute (API) has published recommended practices 752, 753, and 756 which provide guidance for managing the risk from explosions, fires, and toxic material releases to on-site personnel located in new and existing buildings intended for occupancy.

Guidance Documents

(Our experts were on the API committee that recenly updated these documents)

API RP 752 4th Ed. Management of Hazards Associated with Location of Process Plant Permanent Buildings

Provides guidance for managing the risks from process-related explosion, fire, and toxic material release hazards to personnel located in on-site buildings. The RP covers:

  • New and existing permanent buildings

  • New and existing portable buildings (other than light wood trailers) intended for perpetual use (intended to be used for the life of the building or life of the process plant) in a specific, fixed location

API RP 753 2nd Ed. Management of Hazards Associated with Location of Process Plant Portable Buildings

The RP covers:

  • New and existing light wood trailers

  • New and existing portable buildings (other than light wood trailers) intended to be movable and not intended for perpetual use (intended to be used for the life of the structure or life of the plant) in a specific, fixed location.

API RP 756 2nd Ed. Management of Hazards Associated with Location of Process Plant Tents

The RP covers:

  • On-site tents

Guidance documents from API

Why Choose Blast Resource Group?

Our experts have decades of experience performing facility siting studies. Since 2001, they have performed hundreds of studies for refinery and petrochemical sites using the best tools available including PHAST, FLACS, and FACET3D. Our experience includes complex building construction and geometry, complicated indoor process environments, and highly-hazardous chemicals with unique dispersion and explosion behavior characteristics.

Engineer looking at a refinery

Experience

  • We've performed 100's of studies

  • We were on the API committee that developed the facility siting recommended practices

  • We have experience across a wide range of industries: refineries, gas plants, ethylene plants, VCM, chlor-alkali plants, compression, etc...​

  • Analyzed and designed 100's of buildings for blast and fire effects

FLACS dispersion from hydrogen compressor

Software Tools

  • Our experts have developed fully featured facility siting software tools

  • ​We've used PHAST for detailed dispersion and fire analysis for both consequence and QRA studies

  • Our FLACS CFD experience allows us to address complex indoor and outdoor releases while minimizing excess conservatism present in screening methods

  • Using non-linear, dynamic structural analysis methods, including FEA, we can optimize blast-resistant designs for our clients

Metal building framing

Solutions

  • We help clients understand their risks and develop solutions for minimizing that risk

  • Our diverse team has experts who can address building blast damage, window fragment hazards, toxic evacuation risks, and shelter-in-place hazards

  • We have solutions others do not, including full-service supply of blast-resistant pre-engineered metal buildings (PEMB) & blast-resistant modular buildings (BRMs)

  • BRG is the exclusive provider in the US for Gliderol blast resistant roll up doors, the only blast-resistant roll-up doors available in the United States that are designed and tested to withstand explosions

The Facility Siting Process

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Pre-Study

  • Review any corporate facility siting standards

  • Document study methodology, consequence or risk-based

  • Determine the acceptable hazard criteria for explosions, fires, and toxics (consequence-based study) or the acceptable individual and aggregate risk levels (QRA)

  • Make a preliminary list of occupied buildings and process units to include in the study

Item 2 arrow

Facility Siting Study

  • Site visit to survey buildings and develop scenarios with plant process engineers

  • Hazards modeling of explosions, fires, and toxic dispersion impacts

  • Structural modeling of building components for blast response

  • If a risk study, frequency modeling for each scenario to develop the likelihood of a release and hazard outcome

  • Compare results to criteria

  • Document study in a technical report

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Detailed Assessments

  • Computational Fluid Dynamics (CFD) modeling of high consequence dispersion and explosion scenarios to reduce conservatism or include additional physics

  • Detailed fire assessments to account for flame obscuration and evacuation route shielding

  • Develop conceptual building upgrades and construction cost estimates

Item 4 arrow

Remediation

  • Develop a remediation plan for each building exceeding the criteria

  • Determine if building retrofits or replacements are warranted

  • Create a schedule for implementing remediation items

  • Implement interim risk reduction options while waiting to complete remediation items with longer schedules

  • Consider building occupancy management to reduce risk in the interim

Item 5 arrow

Revalidation

  • Monitor for changes that affect facility siting as part of the MOC process

  • Revalidate the facility siting study every 5 years

  • During the revalidation, add new/changed buildings and new process units and account for successful remediation projects

Methodology

A facility siting study (FSS) can be either a consequence-based or risk-based study.

Refinery overpressure contours

Consequence studies evaluate explosion, fire, and toxic hazards and compare the results to predefined criteria such as overpressure, building damage, or thermal radiation limits. The study is less costly and time-consuming compared to a risk study; however, the likelihood of each scenario is not evaluated which makes mitigation prioritization more difficult.

FN risk curves

Risk studies must be quantitative using numerical values for both consequence and frequency. The study must evaluate both individual and aggregate (group) risk. Quantitative risk assessments (QRA) are more complicated and time-consuming than a consequence-only study but have the advantage of being able to show where the highest risk sources originate from which can guide mitigation efforts at the building or in the process.

Remediation

Metal building framework

Following your study, one or more buildings may have exceeded the study criteria. If a consequence study, the hazard type will determine the potential remediation options. For example, if building damage from explosions is high, specific building components may require strengthening. If thermal lethality is high for evacuating personnel, options include additional PPE, alternative exits, or shelter in place. Some common hazard-specific remediation options are:

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Explosion Hazards

  • Structural damage - Perform a conceptual retrofit study to determine the cost and effort of strengthening the building for the blast loads.

  • Window damage - remove, replace with laminated glazing designed for the blast load, or retrofit windows with blast-resistant film and/or catch systems

  • Door damage - Ensure alternative exits are available to facilitate evacuation; replace doors facing the explosion with blast-resistant personnel doors or roll up doors

  • Internal debris - Secure non-structural items such as overhead light fixtures, bookcases, & cabinets that may be thrown during an explosion (includes items mounted to or adjacent to external walls)

Fire Hazards

  • Gas infiltration - Implement procedures and training to close routes of significant flammable gas ingestion such as roll up doors and windows when not in use

  • Jet/pool fires

    • When evacuation is prescribed and all exits are compromised by flame or thermal radiation, consider a detailed fire analysis that considers shielding of the evacuation routes; otherwise, the building may need to be used as short duration shelter in place while the leak is isolated

    • For fire refuge buildings where building ignition and/or window failure due to heat is possible, an evacuation plan is needed and/or retrofit with a fire-resistant exterior component

Toxic Hazards

  • When evacuation is prescribed, provide respiratory escape PPE for the hazard

  • For toxic refuge buildings, 

    • Provide the features listed in API 752 (HVAC isolation, communication, window seals, etc)​

    • Provide indoor air monitoring and procedures so occupants know when to evacuate

    • Provide respiratory escape PPE for the possibility that evacuation is needed

    • Perform a fan ventilation test to determine the buildings air change rate and identify leaks that can be sealed, improving performance and toxic refuge duration​​​​​​

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Often, a more detailed analysis is an option to remove excess conservatism in the original study results. Computational fluid dynamics (CFD) may reduce the blast loads on a building. A fan pressurization test (aka blower door test) may show a lower toxic infiltration rate into a toxic refuge.

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Experienced facility siting practitioners can provide various options for each hazard type ranging from administrative changes to physical retrofits of the building.

Process plant building with windows

Revalidation

  • Revalidation is a verification of the hazard assessment and the occupied buildings

  • It is a chance to incorporate large site changes, such as new process units and new buildings

  • Required every 5 years (29 CFR Part 1910.119 § e.6)​

  • Opportunity to roll detailed studies and smaller efforts back into the main FSS report

  • Update the study to account for any remediation or risk reduction efforts that have been performed to meet recommendations in the last study

  • As remediation efforts can take year, revalidation offers an opportunity to review their progress and adjust if necessary

  • Revalidation is an opportunity to incorporate new knowledge following incidents (near-miss and accidents) that have occurred on-site or in the industry

  • It is a chance to update software versions and results to incorporate the latest state-of-the-art improvements in hazard prediction

  • This can be a good time to evaluate the MOC process to determine if all facility siting-related changes were property addressed via the MOC system

In summary, revalidations are a necessary part of the facility siting lifecycle and should be used to update the study and evaluate risk reduction progress. Depending on the changes at the facility over the preceding 5 years, a revalidation can be as simple as a letter written into the file that nothing has changed or as complex as an update incorporating multiple new buildings and/or process units.

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