When the Industrial Revolution introduced new ways of producing and using energy, the demand for energy surged to fuel the era’s technological advancements.

Chemical plants and power plants were quickly constructed, but the hazards of operating these facilities were not fully appreciated. Incidents such as the deadly accidents in Seveso, Italy, in 1976, and Bhopal, India, in 1984, drew global attention to the dangers.

Workers in the chemical, manufacturing, construction and mining industries are still exposed to risk through the tasks they perform and the substances they handle. But this risk has been reduced, thanks to regulations issued after the Bhopal and Seveso incidents.

The regulations include the Seveso Directive. It seeks to prevent accidents involving dangerous substances, as well as limit the human and environmental consequences of such accidents, should they occur.

The U.S. Occupational Safety and Health Administration (OSHA) implemented regulations (1910.119) in the 1990s for the process safety management of highly hazardous chemicals. The U.S. Environmental Protection Agency (EPA) also published regulations and guidance (40 CFR Part 68) under the Clean Air Act to prevent chemical accidents at facilities that use certain hazardous substances.

Around the same time, the U.K. government released the Control of Major Accident Hazards (COMAH) Regulations, which requires that businesses “take all necessary measures to prevent major accidents involving dangerous substances.”

These regulations offer a framework for Process Safety Management (PSM) and today there are several tools available to help companies ensure safe operations. Among them are the PHA, HAZOP and LOPA – tools that help operations teams manage workplace hazards and prevent risk pathways from developing.

What is a PHA?

Process Hazard Analysis (PHA) helps organizations identify, reduce and manage workplace hazards, which can cause fires, explosions and releases of toxic or flammable chemicals. PHA also helps reduce the downtime caused by an incident.

A PHA is essentially a detailed, step-by-step review of chemical and manufacturing plant operating processes and procedures. It analyzes data on equipment, instrumentation, utilities and human actions, highlighting potential causes of hazardous chemical releases and evaluating their consequences. OSHA and the European Agency for Safety and Health at Work (EU-OSHA) require a PHA for any industrial process that involves hazardous chemicals. Insurance companies and licensing authorities also require them.

What is a HAZOP and how is it related to a PHA?

There are several methods used to conduct a PHA, including the Hazard and Operability study (HAZOP). Other methods include Failure Mode and Effect Analysis (FMEA), “What If” analysis and Checklists.

A HAZOP helps organizations proactively identify and address potential hazards in processes, equipment and facilities. A structured and systematic technique, it is often conducted during facility design and construction to ensure that a system or plant performs as expected. It is also used for existing operation and maintenance processes.

How is the HAZOP conducted?

HAZOP is based on the assumption that risk incidents are caused by deviations from design or operating intentions. Like all PHAs, HAZOPs also identify unintended outcomes to understand their impact on aspects of health and safety.

The team performing the HAZOP must include experts such as engineers, operators, maintenance workers, supervisors and others who have a solid understanding of the HAZOP method and the process under review. Companies often include an engineer who is unfamiliar with the process to provide a different perspective.

Team members document each scenario on worksheets, so the information collected can be reviewed, checked and referenced during and after the study for quality control. Regulators and insurance companies also use the documentation to check for compliance.

Tools Used for a Complex Analysis

A PHA and HAZOP are necessarily complex, due to the sophistication of processes reviewed and the volume of data collected. To meet the documentation challenges presented by that complexity, organizations often turn to software. Sphera’s Process Hazard Analysis (PHA Pro) & HAZOP software provides a way to standardize risk assessment data, record scenarios and ensure that recommendations are followed.

What is LOPA? How does it differ from HAZOP?

Companies also rely on Layer of Protection Analysis (LOPA), defined by the Center for Chemical Process Safety as a method that analyzes independent incident scenarios to compare a scenario risk estimate to its risk criteria. LOPA helps companies determine how many independent protection layers are needed, as well as how much risk reduction each layer needs to provide, for the scenario to fall within the company’s tolerance for risk.

The LOPA and HAZOP are conducted independently, but they complement each other to provide a robust risk assessment. The HAZOP helps companies understand current risks by presenting the full range of possibilities. The LOPA reveals the layers of protection available in case one of those possibilities becomes reality, identifying any weaknesses that exist so they can be addressed.

The Role of the Safety Integrity Level (SIL)

Another critical component of process safety management is functional safety management. Governed by standards such as IEC 61508 and IEC 61511, functional safety management ensures that critical layers of protection for all a facility’s hazards are always in working order and available to protect.

As part of functional safety management, each critical safeguard, known as a Safety Instrumented Function (SIF) must have a Safety Integrity Level (SIL) – a defined level of risk reduction – that it can provide.

SIL calculation determines the risk presented by a specific hazard without the risk reduction benefits of a Safety Instrumented System (SIS). This is known as the unmitigated risk. The figure representing the unmitigated risk is compared to a target for tolerable risk. If the unmitigated risk is higher than the tolerable risk, it must be addressed through a SIF, which is part of a Safety Instrumented System.

Ensuring that each SIF has an actively managed SIL is important for ensuring that overall PSM risk objectives are met. LOPA is a method that is commonly used to determine the SIL required for each SIF in a process.

Process Safety Management Tools: A Summary

Let’s tie them all together once more. The Hazard and Operability Study (HAZOP) and Process Hazard Analysis (PHA) identify your process safety issues. LOPA identifies gaps and where you need to implement Safety Instrumented Functions (SIFs); it determines what Safety Integrity Level (SIL) the SIFs need. The SIFs are part of a Safety Instrumented System (SIS). Everything follows a chain, with each element feeding the next.

Learn More

Companies in the chemical, manufacturing, construction and mining industries can’t function safely without knowledge of the risks and remedies identified through PHA, HAZOP and LOPA analyses. Learn how Sphera’s PHA Pro & HAZOP software helps you conduct robust analyses that provide the actionable intelligence you need.

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