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Course 736 - Introduction to Process Safety Management

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Process Hazard Analysis (PHA)

Introduction

The employer must perform an initial process hazard analysis (hazard evaluation) on all processes covered by the PSM standard.
The employer must perform an initial process hazard analysis (hazard evaluation) on all processes covered by the PSM standard.

A PHA, or evaluation, is one of the most important elements of the process safety management program.

A PHA is an organized and systematic effort to identify and analyze the significance of potential hazards associated with the processing or handling of highly hazardous chemicals.

A PHA provides information that will assist employers and employees in making decisions for improving safety and reducing the consequences of unwanted or unplanned releases of hazardous chemicals.

A PHA analyzes potential causes and consequences of fires, explosions, releases of toxic or flammable chemicals, and major spills of hazardous chemicals.

The PHA focuses on equipment, instrumentation, utilities, human actions (routine and non-routine), and external factors that might affect the process.

The employer must perform an initial process hazard analysis (hazard evaluation) on all processes covered by the PSM standard.

How to Decide Methods Used in PHA's

The process hazard analysis method selected must be appropriate to the complexity of the process and must identify, evaluate, and control the hazards involved in the process.

The selection will be influenced by many factors including how much is known about the process.

  • Is it a process that has been operated for a long period of time with little or no innovation and extensive experience has been generated with its use?
  • Is it a new process or one that has been changed frequently by the inclusion of innovation features?

Also, the size and complexity of the process will influence the decision as to the appropriate PHA method to use.

Limitations of PHA Methods

All PHA methods are subject to certain limitations. Please review the examples below.

  • The checklist method works well when the process is very stable and no changes are made, but it is not as effective when the process has undergone extensive change. The checklist may miss the most recent changes and consequently they would not be evaluated.
  • Another limitation to be considered concerns the assumptions made by the team or analyst. The PHA is dependent on good judgment and the assumptions made during the study need to be documented and understood by the team and reviewer and kept for a future PHA.

Prioritizing PHA’s

First, employers must determine and document the priority order for conducting process hazard analyses. Consideration should be given first to those processes with the potential of adversely affecting the largest number of employees. Other considerations include:

  • the extent of the process hazards;
  • the number of potentially affected employees;
  • the age of the process; and
  • the operating history of the process.

Together, these factors would suggest a ranking order using either a weighting factor system or a systematic ranking method.

The use of a preliminary hazard analysis will assist an employer in determining which process should be of the highest priority for hazard analysis resulting in the greatest improvement in safety at the facility occurring first.

Methods for Conducting the PHA

The employer must use one or more of the following methods, as appropriate, to determine and evaluate the hazards of the process being analyzed:

  • what-if,
  • checklist,
  • what-if/checklist,
  • hazard and operability study (HAZOP),
  • Failure mode and effects analysis (FMEA),
  • Fault tree analysis, or
  • an appropriate equivalent method.

A discussion of these methods of analysis is contained in the publication, OSHA 3133, Process Safety Management Guidelines for Compliance. Whichever method(s) are used, the process hazard analysis must do the following:

  • address the hazards of the process;
  • identify any previous incident that had a potential for catastrophic consequences in the workplace;
  • determine engineering and administrative controls applicable to the hazards and their interrelationships, such as appropriate application of detection methods to provide early warning of releases (acceptable detection methods might include process monitoring and control instrumentation with alarms, and detection hardware such as hydrocarbon sensors);
  • identify the consequences of failure of engineering and administrative controls;
  • address facility siting;
  • address human factors; and
  • conduct a qualitative evaluation of a range of the possible safety and health effects on employees in the workplace if there is a failure of controls.

Different methods for various parts of the process may be used. For example, a process involving a series of unit operations of varying sizes, complexities, and ages may use different methods and team members for each operation. Then the conclusions can be integrated into one final study and evaluation.

The PHA Team

OSHA believes that the process hazard analysis is best performed by a team with expertise in engineering and process operations. The team conducting the PHA needs to understand the method that is going to be used. The PHA team should include:

  • at least one employee who has experience with and knowledge of the process being evaluated; and
  • one member (preferably the team leader) knowledgeable in the specific analysis methods and proper implementation of methods being used in the evaluation.

The other full or part-time team members need to provide the team with expertise in areas such as:

  • process technology;
  • process design;
  • operating procedures and practices;
  • alarms;
  • emergency procedures;
  • instrumentation;
  • maintenance procedures, both routine and non-routine tasks, including how the tasks are authorized;
  • procurement of parts and supplies;
  • safety and health; and
  • any other relevant subjects.

The ideal team will have an intimate knowledge of the standards, codes, specifications, and regulations applicable to the process being studied. The selected team members need to be compatible and the team leader needs to be able to manage the team and the PHA study. The team needs to be able to work together while benefiting from the expertise of others on the team or outside the team to resolve issues and to forge a consensus on the findings of the study and recommendations.

Employer Response to PHA Team Findings

In response to the PHA Team’s findings and recommendations, the employer must establish a system to:

  • address promptly the team's findings and recommendations
  • ensure that the recommendations are resolved in a timely manner and that the resolutions are documented;
  • document what actions are to be taken;
  • develop a written schedule of when these actions are to be completed;
  • complete actions as soon as possible; and
  • communicate the actions to operating, maintenance, and other employees whose work assignments are in the process and who may be affected by the recommendations or actions.
The process hazard analysis must be <u>updated and revalidated</u> at least every five years.
The process hazard analysis must be updated and revalidated at least every five years.
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Review and Revalidation

At least every five years after the completion of the initial process hazard analysis, the process hazard analysis must be updated and revalidated by a team meeting the standard's requirements to ensure that the hazard analysis is consistent with the current process.

Employers must keep on file and make available to OSHA, upon request, process hazard analyses and updates or revalidation for each process covered by PSM, as well as the documented resolution of recommendations, for the life of the process.

Instructions

Before beginning this quiz, we highly recommend you review the module material. This quiz is designed to allow you to self-check your comprehension of the module content, but only focuses on key concepts and ideas.

Read each question carefully. Select the best answer, even if more than one answer seems possible. When done, click on the "Get Quiz Answers" button. If you do not answer all the questions, you will receive an error message.

Good luck!

1. A _______ is an organized and systematic effort to identify and analyze the significance of potential hazards associated with the processing or handling of highly hazardous chemicals.

2. The employer must perform an initial process hazard analysis on which of the following processes covered by the PSM standard?

3. All of the following are methods to determine and evaluate the hazards of a process being analyzed, EXCEPT:

4. At least every ____ years after the completion of the initial process hazard analysis, the process hazard analysis must be updated and revalidated.

5. OSHA believes that the process hazard analysis is best performed by a team with which of the following areas of expertise?


Have a great day!

Important! You will receive an "error" message unless all questions are answered.