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Facility Siting: Risk-Based Solutions and Benefits

Extreme Loads and structural risk

Facility Siting: Risk Based Solutions and Their Benefits

Facility Siting is part of the Process Hazard Assessment (PHA) requirement in Process Safety Management (PSM) per CFR 1910.119. API 752/753/756 provides a recommended practice for how to perform a facility siting study.

There are many approaches to facility siting which ultimately fall under two categories: Consequence or Risk-based. A risk-based approach to facility siting, which considers the frequency of scenarios, can provide the greatest understanding of on-site risks and enables the most cost-effective resolution of facility siting issues.

ABS Group's experience in consequence and risk-based facility siting assessments, hazard mitigation and structural engineering provides a one-stop solution to risk-based assessment and hazard mitigation.

Facility Siting

What is a Quantitative Risk Assessment?

A Quantitative Risk Assessment (QRA) is a systematic approach to calculating risk. It provides a clear, quantifiable understanding of potential risk exposure to personnel, assets, the environment and your business. In addition, a QRA evaluates the validity of quantitative results by identifying critical assumptions and risk-driving elements. A QRA involves predicting the consequences of a hazard and the frequency at which the threat may occur. These aspects are then combined to obtain numerical values for fatality risk.

QRA studies are invaluable for production and processing facilities, high-pressure pipelines and storage and importation sites, including Liquefied Natural Gas (LNG)

Utilizing a risk-based approach for facility siting improves decision-making by highlighting scenarios that contribute most to your overall risk.

This approach ensures you meet acceptable individual, operational and environmental criteria demonstrating that risk is As Low As Reasonably Practicable (ALARP).

Implementing QRA: Going Beyond Software 

When it comes to conducting QRAs, there are various commercial and private software tools. While these tools can identify hazards, quantify exposure and calculate risk, this is often where their capabilities stop, resulting in an unclear path forward. While you may better understand your hazard risk, the question of what to do next is not always apparent.

Common questions you may be left answering alone are:

  1. "How can additional modeling of select controlling scenarios improve my risk?"
  2. "How do I retrofit a building when I do not have design loads or occupancy established?"
  3. "Without clear hazard contours, where can I site blast-resistant buildings, trailers and other portable or temporary buildings?"
  4. "What is the best cost-effective solution to protect occupants of a building from hazards?"

A QRA is not just about having a software tool and running complex multivariate analysis. You need practical experience in deriving points of action from the QRA so that you can properly manage your operational risk. The QRA process should identify the hazard source so you can develop emergency response plans, adjust occupancy retrofit structures, locate new permanent and temporary buildings and install automated detection systems.

Our Unique Approach to QRA

ABS Group offers a global multidisciplinary network of engineers and a full scope of risk-based analysis experience and tools in a cradle-to-grave approach. In addition, we possess the ability to integrate detailed consequence modeling such as Computational Fluid Dynamics (CFD). Our QRA process utilizes a data-intensive approach in identifying scenarios by including all process equipment with hazard potential and modeling a wide range of release sizes and historical weather conditions.

We have developed software tools such as FACET3D, proprietary data analysis and frequency prediction spreadsheets to model a range of unique outcomes.

Understanding Your Risk

We offer our clients a three (3) step solution:

  1. Understand the Risk
  2. Analyze the Risk
  3. Mitigate the Risk

Below are the main steps involved in a typical QRA study, including how the outputs feed into the next phase of the process.

Understanding Risk

ABS Group provides our clients with a comprehensive, detailed report that defines inputs, explains calculation methodology and summarizes results in meaningful tables and figures (as shown below). We also offer mitigation options to target the most notable contributors to the total risk.

Individual and Aggregate Risk Results Summary - Example

Graph

The Benefits of QRA

Controlling Risk Sources

One large benefit of a QRA is that it identifies the controlling risk sources. Since scenarios are developed across the process, risk results are ranked by scenario to indicate which processes provide the highest risk and are good candidates for risk reduction via process controls and hazard mitigation. We provide individual risk for each scenario and aggregate risk (in the form of risk indices) by scenario and hazard type. Targeted mitigation has a significant risk reduction impact across the facility using these results. Examples of these mitigation measures include:

  • Leak isolation via LEL detection and isolation
  • More frequent and extensive mechanical inspections to identify degrading equipment
  • Replacement of high leak frequency equipment with low-frequency alternatives (welded pipe for flanges; double seal pumps)
  • Installation of explosion suppression water deluge systems
  • Building isolation and sealing to prevent toxic infiltration
  • Evacuation PPE for toxic and fire hazards

Building Occupancy

Building occupancy has a direct impact on calculated risks. The most hours worked by any individual determines the time fraction used for individual risks. Therefore, reducing the time spent in the building directly reduces the individual risk. Over a week, the total number of people in the building impacts the aggregate risk. In some cases, moving people to lower-risk buildings can be an acceptable risk mitigation strategy. QRA requires a company to have quantitative risk criteria for individual and aggregate risk. Quantitative criteria development requires understanding the different risk criteria, the best practices for developing the criteria and the industry risk criteria precedents.

Since we wrote the book on developing and applying quantitative risk criteria, entitled Guidelines for Developing Quantitative Safety Risk Criteria, published by CCPS, we are well-positioned to help companies navigate the quantitative risk criteria development process. 

Interpreting the risk results when compared to the criteria is often a point of confusion. Individual risk is straightforward since most companies define a maximum criteria value above which risk reduction is required. Aggregate risk illustrated as FN curves are more complex, consisting of an intolerable upper region, an ALARP middle region and a broadly acceptable lower region. The intolerable region requires risk reduction, while the ALARP region requires more risk assessment and risk reductions when practicable. Risk reductions are viable when the effort and cost are not disproportionate to the potential benefits achieved.

Companies must decide how current to keep their risk studies. PSM defines a 5-year revalidation cycle for facility siting in the US. PSM also requires the Management Of Change (MOC) program to evaluate the impact of significant facility changes. It is not reasonable or practical to update the QRA for every process change; however, some level of risk impact should be performed for significant process unit changes or the addition of new occupied buildings. Minor changes like replacing a pump can be documented and addressed during the next QRA revalidation cycle.

Why ABS Group?

ABS Group is uniquely positioned based on experience to provide clients with facility siting using risk-based methods. Risk-based facility siting offers a more rigorous study of potential significant accident hazards. It is crucial for industry PSM to understand the minimum requirements for a QRA and what to look for when interpreting QRA studies. Working with industry experts like us provides easy solutions to the complex issues surrounding QRAs.

Evaluating impacts and doing cost-benefit are usually the limits for most consultants. We offer a solution-focused approach, with the QRA being the starting point in the journey toward safer operations. Risk ranking and prioritization, mitigation planning, cost-benefit studies, design, and implementation planning, allow us to provide a turnkey solution for the facility siting lifecycle.

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