Of the several “approved” types of Process Hazards Analysis (PHA), the “Hazard and Operability” (HAZOP) study is the most widely used PHA technique in the chemical, pharmaceutical, oil and gas, and nuclear industries worldwide. HAZOP is used during the design stages of a new process or project, for major process modifications, and for periodic review of existing operations. This method has been found to be very effective in identifying and analyzing the risks of potentially hazardous process operations and in identifying operability problems.
The Hazard and Operability (HAZOP) analysis methodology is a systematic team-based Process Hazards Analysis (PHA) technique.
The U.S. Occupational Safety and Health Administration (OSHA) recognizes the HAZOP technique as an acceptable methodology for conducting PHA’s of processes that are covered by the OSHA Process Safety Management standard. Other regulators around the world also accept the HAZOP methodology as appropriate for analyzing the existing and potential hazards of a complex process that involves a highly hazardous substance.
Although the HAZOP method is highly structured – in the application of Guide Words to Process Parameters – in practice, the quality of the study is influenced by the ability of the HAZOP Leader to ask the appropriate questions. The objective is to ensure that the team identifies all the hazards of the process being studied, not only the most obvious hazards. Thus, the outcome of the study is based on the Leader’s experience, with the HAZOP technique, with the process being analyzed, with process-control systems, and with unit operations, in general.
Our large team of highly-qualified HAZOP leaders and process-safety resource experts has facilitated hundreds of HAZOP-based PHA’s worldwide, in virtually all sectors of the process and processing industries. Our Team Leaders are chemical and/or process engineers with a high level of process safety expertise and knowledge, and with many years of experience leading HAZOPs in industry and as consultants.
We can facilitate HAZOPs, and other types of PHAs, in a large number of languages, including English, Spanish, Chinese, French, German, Italian, Arabic and Hindi. Our worldwide presence helps ensure intimate knowledge of local codes, standards, and cultures. Combined with our expertise in process safety engineering, material-testing capabilities, interpretation of test results, and ready access to process safety data, Chilworth provides a HAZOP capability unrivalled in our market.
Moreover, through the Chilworth Process Safety Academy, we train and qualify a large number of HAZOP leaders every year. We provide HAZOP leader training through our public-enrollment courses as well as private company training, which can be tailored to our clients’ specific needs.
Our approach is to use a structured HAZOP to identify the hazards of a process and – as a by-product – to identify potential operating problems. The emphasis is on evaluating the basic control system, providing effective emergency controls, preventing the release of hazardous materials, and mitigating the consequences of a loss of process control or a hazardous-material release. We provide a semi-quantitative HAZOP risk analysis that incorporates the philosophies of Layers of Protection Analysis (LOPA), Safety Instrumented Systems (SIL), and Fault Tree Analysis (FTA) to assess the reliability of process controls and number and type of risk reduction measures (safeguards) that might be needed.
The general steps involved in conducting a HAZOP include:
- A review of the available Process Safety Information (PSI) and identification of missing PSI that is required to support the HAZOP, including:
- Hazardous materials properties including combustibility, flammability, explosivity, reactivity, self-heating, toxicity, electrostatic properties
- Process description
- Process flow sheets
- Operating procedures
- Piping and instrumentation drawings (P&IDs)
- Equipment design specifications
- Pressure relief systems specifications
- Site and industry data concerning process-component failure frequencies and probabilities of failure on demand (PFD).
- The HAZOP study would involve the following procedure:
- Establishing the “Design Intent” for the process, including the desired and/or safe ranges for each of the operating parameters
- Applying the Guide Words (No, Less, More, Reverse, etc.) to each of the Process Parameters (Temperature, Pressure, Flow, Level, etc.), to identify deviations from the design intent
- Determining if the control system and emergency systems are adequate and are sufficiently reliable to prevent each deviation from escalating to an undesirable process incident
- Estimating the severity of the consequences of each undesired incident. Consequences can be further evaluated using our expertise in consequence modeling with specialist software such as PHAST® and Effects®
- Estimating the likelihood of occurrence of each undesired incident
- Utilizing a Risk Matrix to determine the relative risks of the undesired incidents
- Comparing the risk of occurrence for each incident with corporate guidelines for process risk
- Determining the number and types of safeguards and/or process improvements that would be needed to reduce the risks to negligible or tolerable risks
- At the conclusion of the HAZOP analysis, our process safety specialist will present the results of observations, the findings and conclusions of the analysis, and preliminary recommendations and suggestions, to members of the site management staff.
Report and Documentation
Shortly after the HAZOP team’s study, the process safety engineer will submit a written draft report to the client that will contain the results of the study, for comments by the client. Our process safety specialist’s report will present the HAZOP Team’s recommendations and suggestions for improvements to the process, as based on the site’s experience and on recognized and generally-accepted good engineering practices. Following the receipt of comments from the client, a final report is issued.