How Understanding Chemical Process Hazards Can Help Enhance Process Safety Management
Introduction
Understanding chemical process hazards is crucial for ensuring the safety and efficiency of industrial operations. Before conducting a Process Hazard Analysis (PHA), it is essential to have a comprehensive understanding of Process Safety Information (PSI). This foundational knowledge is critical for identifying and evaluating potential hazards, thereby preventing incidents and ensuring regulatory compliance. Saltegra, a leading Process Safety Management (PSM) consulting firm based in California, emphasizes the importance of PSI awareness training and thorough process hazard analysis (PHA) to mitigate risks associated with chemical processes.
PSI includes detailed information about the chemicals used in a process, the technology involved, and the equipment associated with the process. PSI is crucial because it provides the necessary safety data to understand the hazards and risks associated with chemical processes.
This information helps in designing safe processes, implementing effective safety measures, and preparing for potential emergencies. An accurate and comprehensive PSI ensures facilities operate within safe limits and comply with regulatory requirements. Federal facilities handling Highly Hazardous Chemicals (HHCs) can comply with Process Safety Management (PSM) regulations by maintaining up-to-date PSI, which forms the basis for effective hazard identification and risk management strategies.
Types of Hazardous Substances
The American Institute of Chemical Engineers defines hazard as “an inherent chemical or physical characteristic that has the potential for causing damage to people, property, or the environment.” Hence, chemical process hazards encompass substances with inherently hazardous properties classified by the Australian Institute of Health and Safety as flammable substances, explosive substances, oxidizing substances, corrosive substances, gases under pressure, reactive and incompatible substances, steam, combustible dusts, inert gases, and acutely toxic substances.
Flammable Substances
Flammable substances include solids, liquids, gases, liquefied gases, aerosols/mists, and atmospheres that could ignite when specific conditions are met. The ignition of a flammable substance requires three elements, commonly known as the “fire triangle:” fuel, oxidant (usually oxygen in the air), and an ignition source.
The prevention of fires often focuses on preventing the formation of flammable atmospheres due to the ubiquitous nature of ignition sources.
The table below offers useful definitions from the Center for Chemical Process Safety (CCPS) related to flammable materials, along with examples and common interpretations of these properties.
| Lower Flammability Limit (LFL) | The lowest concentration of a gas or vapor in air capable of producing a flash of fire in the presence of an ignition source | Propane: 2.1% by volume in air | Below this limit, the mixture is too lean to burn |
| Upper Flammability Limit (UFL) | The highest concentration of a gas or vapor in air capable of producing a flash of fire in the presence of an ignition source | Propane: 9.5% by volume in air | Above this limit, the mixture is too rich to burn |
| Autoignition Temperature (AIT) | The lowest temperature at which a substance will spontaneously ignite without an external source of ignition | Ethanol: 363°C (685°F) | Temperature at which a substance can self-ignite |
| Flash Point | The lowest temperature at which a liquid can form an ignitable mixture in air near the surface of the liquid | Gasoline: -43°C (-45°F) | Below this temperature, the liquid will not produce enough vapor to ignite |
| Fire Point | The temperature at which a liquid produces enough vapor to sustain a continuous flame | Kerosene: 38-72°C (100-162°F) | A few degrees higher than the flash point, where sustained burning occurs |
Explosive Substances
The Globally Harmonized System (GHS) defines an explosive substance as one capable of producing gas at high temperatures and pressures, causing damage to the surroundings. Explosive properties arise from the presence of certain chemical groups that react to produce rapid increases in temperature or pressure. Unlike explosive atmospheres, explosive substances do not require atmospheric oxygen to sustain the reaction. These substances can either be specifically formulated to produce explosive effects (e.g., trinitrotoluene or TNT) or may explode accidentally (e.g., ammonium nitrate).
Oxidizing Substances
Oxidizers are substances that produce oxygen during reactions under specific conditions, fueling fires or causing redox reactions. Oxidizing substances can be solids (e.g., metal peroxides, ammonium nitrate), liquids (e.g., hydrogen peroxide, nitric acid), or gases (e.g., oxygen, fluorine, chlorine). These substances can significantly enhance the intensity of fires or cause hazardous reactions.
Corrosive and Reactive Substances
Corrosive substances can damage equipment and structures by undergoing redox reactions with construction materials, leading to structural failure. The corrosiveness of a substance may depend on storage conditions. Common types of corrosion include general corrosion, scaling, exfoliation, galvanic corrosion, crevice corrosion, pitting, and stress-related corrosion, such as stress corrosion cracking and corrosion fatigue.
In California, facilities handling corrosive substances must conduct a Damage Mechanism Review (DMR) to identify and evaluate potential damage mechanisms, such as corrosion and fatigue, that could affect process equipment integrity. Design and construction should account for the risk of corrosion, either by selecting appropriate materials or adding a corrosion allowance.
Reactive substances, such as monomers and resins, tend to react and change form, often exothermically, increasing the reaction rate and generating more heat. Controlling these reactions requires strict regulation of temperatures and pressures. Incompatible substances react together to produce undesirable outcomes, such as toxic, corrosive, or reactive products, which can result in hazardous temperature or pressure changes.
Gases Under Pressure
Storing gas under pressure poses significant hazards due to the potential energy stored. Rapid release of pressurized gas can result in powerful jets, vessel movement, cooling and embrittlement issues, erosion, and catastrophic failure. Managing these risks requires robust design and maintenance practices to prevent sudden releases and ensure structural integrity.
Acutely Toxic Substances
Many chemicals used in industrial processes are acutely toxic to human health and the environment. Acute toxic exposures often result from containment loss during process malfunctions, fires, or explosions. Such exposures can occur through direct release or as a result of emergency response actions, such as fire water runoff contaminating local waterways.
Other Hazardous Substances
Steam is commonly used in industrial processes for power, heating, purging equipment, or as part of the process itself. Steam at high temperatures and pressures can cause severe burns, thermal expansion, and potentially dangerous conditions like water hammer, which can lead to pipe ruptures. Steam jets can also produce static electricity, acting as an ignition source.
Combustible dusts, such as those from organic materials (e.g., sugar, flour) and metals, can cause explosions when suspended in the air with an ignition source present. Managing dust hazards involves controlling dust accumulation and eliminating ignition sources to prevent explosions
Inert gases like carbon dioxide, nitrogen, helium, and argon are among the most common dangerous chemicals you can find in workplaces. They are used to create non-flammable atmospheres. While effective for fire prevention, these gases pose asphyxiation hazards to humans by displacing oxygen. This is particularly dangerous in confined spaces, requiring stringent safety protocols to ensure safe working conditions.
Process Safety Information
Process Safety Information (PSI) is a critical component of Process Safety Management (PSM) that provides detailed information about hazardous chemicals, technology, and equipment used in processes. Apart from conducting effective PHA with a well-trained facilitator, accurate and comprehensive PSI is also essential for ensuring safe operations in chemical-processing companies in California. Here are the common PSIs required by OSHA 29 CFR 1910.119 – Process Safety Management of Highly Hazardous Chemicals:
Information on Hazardous Chemicals
| Chemical Properties | Physical state (solid, liquid, gas), vapor pressure, flash point, autoignition temperature |
| Health Hazards | Toxicity, exposure limits, and health effects |
| Physical Hazards | Flammability, explosiveness, and reactivity |
| Safety Data Sheets (SDSs) | Essential safety and handling information |
Information on Process Technology
| Block Flow Diagrams & PFDs | Visual representations of process flow and operations |
| Process Chemistry | Details of chemical reactions, including reactants, products, and conditions (temperature, pressure) |
| Maximum Intended Inventory | Maximum quantity of hazardous chemicals present in the process |
| Safe Upper and Lower Limits | Established limits for temperature, pressure, flow, and composition |
| Consequences of Deviation | Analysis of potential consequences when operating outside safe limits |
Information on Process Equipment
| Specifications & Design Codes | Design and construction details, materials, codes, and standards |
| Piping and Instrumentation Diagrams (P&IDs) | Detailed diagrams of piping, instrumentation, and control systems |
| Relief System Design | Design details of pressure relief systems, including valves and vent systems |
| Electrical Classification | Classification of areas with flammable gases, vapors, or dusts and appropriate electrical equipment |
| Safety Systems | Information on safety systems such as interlocks, alarms, and automatic shutdowns |
Information on Safety Systems
| Interlocks | Systems preventing operation unless certain conditions are met |
| Alarms and Warning Devices | Systems alerting operators to unsafe conditions |
| Automatic Shutdown Systems | Systems automatically shutting down processes or equipment under unsafe conditions |
Conclusion
Chemical process hazards are complex and multifaceted, requiring comprehensive understanding and management to ensure safety in industrial environments. Addressing hazardous substances, ignition sources, and operating conditions is critical to preventing incidents and ensuring safe operations. Compliance with PSI requirements involves maintaining detailed records of chemical properties, process technology, and equipment specifications, as well as ensuring that safety systems are properly designed and implemented.
Saltegra Consulting LLC , based in California, underscores the importance of PSM training and thorough PHA to enhance safety and compliance with federal and state regulations. Our commitment to providing affordable and tailored operational risk management and compliance services helps small, medium, and corporate-level clients navigate the complexities of chemical process safety. This ensures that people and the environment are protected from potentially catastrophic events. By conducting comprehensive PHAs supported by accurate and up-to-date PSI, industries can achieve safer and more reliable operations.
