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Approved PHA Methodologies

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Approved Process Hazard Analysis Methodologies

As stated within the Process Safety Management (29 CFR 1910.119) and Risk Management (40 CFR Part 68) program standards, there are six approved methodologies for conducting a Process Hazard Analysis. This article will take a closer look at a brief description and the purpose of each approved methodology.


WHAT-IF

The What-If Analysis technique is a brainstorming approach in which a group of experienced staff familiar with the subject process ask questions or voice concerns about possible undesired events. The purpose of a What-If Analysis is to identify hazards, hazardous situations, or specific event sequences that could produce undesirable consequences. An experienced group of people identifies possible abnormal situations, the consequences, and existing safeguards, then suggests alternatives for risk reduction where obvious improvement opportunities are identified or where safeguards are proved to be inadequate. This method can involve examination of possible deviations from the desired intent that could result in an incident. This is a powerful technique if the staff is experienced in the system process. Otherwise, the results are likely to be incomplete.


CHECKLIST

A Checklist Analysis uses a written list of items, or procedural steps, to verify the status of a system. Traditional checklists vary in terms of detail and are frequently used to indicate compliance with standards and practices. This methodology is commonly used in combination with another hazard evaluation method to identify hazards that the checklist alone might miss. The purpose of traditional checklists is to ensure that organizations are complying with standard practices. Checklists can be used to familiarize inexperienced personnel with a process by having them compare a process’s conditions to the checklist requirements. Checklists can also be used as a basis for management review of the assessments of a process or operation.


WHAT-IF / CHECKLIST

The What-If / Checklist Analysis is a technique that combines the brainstorming approach of the What-If Analysis with the systematic features of the Checklist Analysis.

The purpose of the What-If / Checklist Analysis is to identify hazards, consider the general types on incidents that can occur in a process or activity, evaluate in a qualitative way the effects of the incidents, and determine whether the safeguards against potential incidents are adequate. The hazard evaluation team will then suggest ways to reduce the risk of operating the process.


HAZARD AND OPERABILITY STUDY

The Hazards and Operability Study, also known as a HAZOP Analysis, is a technique that was developed to identify and evaluate safety hazards in a process facility, and to identify operability problems that could compromise the facility’s ability to achieve the designed productivity. The purpose of a HAZOP Analysis is to carefully review a process or operation in a systematic fashion to determine whether deviations from a design or operational intent can lead to undesirable consequences. This technique can also be used to evaluate written procedures. The hazard evaluation team lists the potential causes and consequences of the deviations as well as the existing safeguards that provide protection against the deviations. When the team determines that inadequate safeguards exist for a deviation, they will recommend corrective action that should be taken to reduce the associated risk.


FAILURE MODES AND EFFECTS ANALYSIS

A Failure Modes and Effects Analysis, also referred to as FMEA, tabulates failure modes of equipment and their effects on a system or facility. The failure mode describes how equipment fails such as open, closed, on, off, or leaks. The effect of the failure mode is determined by the system’s response to the equipment failure.

The purpose of a Failure Modes and Effects Analysis is to identify single equipment and system failure modes and each failure mode’s potential effects on the system or facility. This analysis typically generates corrective action recommendations for increasing system reliability, thus improving process safety.


FAULT TREE ANALYSIS

Fault Tree Analysis, also referred to as FTA, is a deductive technique that focuses on one particular incident or main system failure and provides a method for determining causes of that event. The purpose of a Fault Tree Analysis is to identify combinations of equipment failures and human errors that can result in an incident. FTA is well suited for analyses of highly redundant systems. For systems particularly vulnerable to single failures that can lead to incidents, it is better to use a single-failure-orientated technique such as FMEA or HAZOP Study. FTA is often utilized in situations where another hazard evaluation technique has pinpointed an important incident of interest that requires a more detailed analysis.

 

Regardless of which methodology is selected, the Process Hazard Analysis must address the hazards of the process, the identification of any previous incident which had a likely potential for catastrophic consequences in the workplace, engineering and administrative controls applicable to the hazards and their interrelationships such as appropriate application of detection methodologies to provide early warning of releases, consequences of failure of engineering and administrative controls, facility siting, human factors, and a qualitative evaluation of a range of the possible safety and health effects of failure of controls on employees in the workplace.


References - 

CCPS - Center for Chemical Process Safety, OSHA 29 CFR 1910.119, EPA 40 CFR Part 68


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The approved PHA methodologies.
Approved PHA Methodologies

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