🦫Intro to Chemical Engineering Unit 12 – Safety and Risk Management in Chemical Engineering
Safety and risk management are crucial aspects of chemical engineering, focusing on identifying, assessing, and mitigating potential hazards in industrial processes. This unit covers key concepts, techniques, and regulations that help engineers design and operate safer systems, minimizing risks to people, property, and the environment.
From hazard identification methods to emergency response planning, students learn a comprehensive approach to safety. Case studies of major industrial accidents provide valuable lessons, emphasizing the importance of proactive safety measures, effective communication, and continuous improvement in process safety culture.
Hazard a potential source of harm or adverse health effect on a person or persons
Can be classified as physical, chemical, biological, or ergonomic
Risk the likelihood and severity of a hazard causing harm
Assessed by considering both the probability and consequences of an event
Safety the control of recognized hazards to achieve an acceptable level of risk
Involves identifying, evaluating, and mitigating potential dangers
Process Safety Management (PSM) a systematic approach to preventing and mitigating the consequences of catastrophic releases of toxic, reactive, flammable, or explosive chemicals
Inherent Safety the concept of designing processes and equipment to eliminate or minimize hazards, rather than relying on add-on safety systems
Includes principles such as substitution, minimization, moderation, and simplification
Layer of Protection Analysis (LOPA) a semi-quantitative risk assessment method that identifies independent protection layers (IPLs) and estimates the risk reduction achieved by each layer
Fault Tree Analysis (FTA) a top-down, deductive failure analysis method that uses Boolean logic to combine a series of lower-level events and determine the probability of a top event occurring
Hazard Identification Techniques
Preliminary Hazard Analysis (PHA) a qualitative technique used early in the design process to identify potential hazards and assess their severity and likelihood
Hazard and Operability Study (HAZOP) a systematic, team-based approach that examines each part of a process to identify potential deviations from the intended design and their consequences
Uses guide words (e.g., "no," "more," "less") to prompt discussion and identify hazards
What-If Analysis a brainstorming technique that uses a series of questions to identify potential hazards and their consequences
Often combined with checklist analysis to ensure comprehensive coverage
Failure Mode and Effects Analysis (FMEA) a bottom-up, inductive analysis technique that identifies potential failure modes, their effects, and the criticality of each failure
Checklist Analysis a technique that uses pre-established lists of hazards, requirements, or best practices to identify potential issues and ensure compliance
Consequence Analysis a quantitative technique that models the potential effects of a hazardous event, such as a chemical release or explosion
Uses tools like dispersion modeling and fire and explosion modeling to estimate the impact on people, property, and the environment
Risk Assessment Methods
Quantitative Risk Assessment (QRA) a method that uses numerical data and models to estimate the probability and consequences of potential hazards
Involves techniques such as event tree analysis, fault tree analysis, and consequence modeling
Semi-Quantitative Risk Assessment a method that uses a combination of numerical and qualitative data to estimate risk
Techniques include risk matrices, risk graphs, and calibrated risk assessment
Qualitative Risk Assessment a method that uses descriptive scales (e.g., high, medium, low) to categorize the likelihood and severity of potential hazards
Often used as a screening tool to prioritize risks for further analysis
Risk Matrix a tool that combines the likelihood and severity of a hazard into a single risk rating
Helps prioritize risks and determine appropriate risk reduction measures
As Low As Reasonably Practicable (ALARP) a principle that states that risks should be reduced to a level that is as low as reasonably practicable, considering the costs and benefits of risk reduction measures
Risk Acceptance Criteria the level of risk that is deemed acceptable by an organization or society
Can be based on factors such as industry standards, regulatory requirements, and societal expectations
Safety Regulations and Standards
Occupational Safety and Health Administration (OSHA) a U.S. federal agency that sets and enforces standards for workplace safety and health
Relevant standards include the Process Safety Management (PSM) standard (29 CFR 1910.119) and the Hazard Communication standard (29 CFR 1910.1200)
Environmental Protection Agency (EPA) a U.S. federal agency responsible for protecting human health and the environment
Administers the Risk Management Plan (RMP) rule (40 CFR Part 68), which requires facilities that use certain hazardous substances to develop and implement risk management programs
National Fire Protection Association (NFPA) a U.S.-based nonprofit organization that develops and publishes consensus codes and standards related to fire, electrical, and life safety
Relevant standards include NFPA 30 (Flammable and Combustible Liquids Code) and NFPA 70 (National Electrical Code)
American Institute of Chemical Engineers (AIChE) a professional organization that develops and disseminates best practices and technical resources for chemical engineering
Publishes the Center for Chemical Process Safety (CCPS) guidelines, which provide guidance on process safety management and risk assessment
International Organization for Standardization (ISO) an international standard-setting body that develops and publishes standards for various industries
Relevant standards include ISO 45001 (Occupational Health and Safety Management Systems) and ISO 31000 (Risk Management)
Process Safety Management
Process Safety Information (PSI) the collection and documentation of information necessary to conduct a process hazard analysis and operate a process safely
Includes information on the hazards of the chemicals used, the technology of the process, and the equipment in the process
Process Hazard Analysis (PHA) the identification and evaluation of hazards associated with a process, and the identification of necessary control measures
Must be updated every five years or when a major change occurs
Operating Procedures written instructions that provide clear, step-by-step directions for safely conducting activities involved in each covered process
Must be reviewed and certified annually
Training the provision of initial and refresher training to ensure that employees understand the hazards of the process and the procedures for safe operation
Must be documented and verified
Mechanical Integrity (MI) the establishment and implementation of written procedures to maintain the ongoing integrity of process equipment
Includes inspection, testing, and preventive maintenance of equipment such as pressure vessels, piping systems, relief and vent systems, and emergency shutdown systems
Management of Change (MOC) the establishment and implementation of written procedures to manage changes to process chemicals, technology, equipment, and procedures
Ensures that the impact of changes on safety and health is evaluated and controlled
Pre-Startup Safety Review (PSSR) the confirmation that construction and equipment are in accordance with design specifications, safety and operating procedures are in place, and process hazard analysis recommendations have been addressed prior to introducing highly hazardous chemicals to a process
Accident Prevention Strategies
Inherently Safer Design the concept of eliminating or reducing hazards through the selection of less hazardous materials, minimizing inventory, and designing simpler, more robust processes
Applies principles such as substitution, minimization, moderation, and simplification
Layers of Protection the use of multiple, independent safeguards to prevent or mitigate the consequences of a hazardous event
Includes passive, active, and procedural safeguards
Safety Instrumented Systems (SIS) a system composed of sensors, logic solvers, and final elements designed to bring a process to a safe state when predetermined conditions are violated
Designed and managed according to standards such as IEC 61508 and IEC 61511
Permit-to-Work Systems a formal, written system used to control certain types of work that are potentially hazardous
Ensures that work is properly authorized, the hazards are identified and controlled, and communication between work groups is effective
Management of Change (MOC) Procedures a systematic approach to evaluating and controlling the risks associated with changes to a process
Ensures that the impact of changes on safety, health, and the environment is thoroughly assessed and managed
Process Safety Culture the shared values, beliefs, and behaviors that determine how an organization views and manages process safety
Includes elements such as leadership commitment, employee involvement, open communication, and continuous improvement
Human Factors the study of how people interact with their work environment, tools, and equipment
Considers factors such as workload, fatigue, communication, and human-machine interface design to optimize human performance and minimize the potential for human error
Emergency Response Planning
Emergency Response Plan (ERP) a written document that outlines the actions to be taken in the event of an emergency, such as a fire, explosion, or chemical release
Includes elements such as emergency contact information, evacuation procedures, and roles and responsibilities of emergency response personnel
Incident Command System (ICS) a standardized approach to the command, control, and coordination of emergency response
Provides a common hierarchy and structure for managing resources and communication during an incident
Emergency Notification Systems systems used to alert personnel of an emergency and provide instructions for appropriate response
Can include audible and visual alarms, text messaging, and email notifications
Evacuation Procedures pre-planned procedures for safely and efficiently evacuating personnel from a facility in the event of an emergency
Includes elements such as evacuation routes, assembly points, and head count procedures
Shelter-in-Place Procedures pre-planned procedures for safely sheltering personnel within a facility in the event of an emergency where evacuation is not possible or advisable
Includes elements such as shelter locations, air handling system controls, and communication protocols
Emergency Drills and Exercises regularly scheduled simulations of emergency scenarios used to test and improve emergency response capabilities
Can include tabletop exercises, functional drills, and full-scale exercises
Post-Incident Investigation a systematic process for gathering and analyzing information about an incident to determine its causes and identify corrective actions to prevent recurrence
Includes elements such as root cause analysis, timeline development, and recommendations for improvement
Case Studies and Lessons Learned
Bhopal Disaster (1984) a catastrophic chemical release at a Union Carbide pesticide plant in Bhopal, India, resulting in thousands of deaths and injuries
Lessons learned include the importance of inherent safety, effective emergency response, and corporate responsibility
BP Texas City Refinery Explosion (2005) a series of explosions and fires at a BP refinery in Texas City, Texas, resulting in 15 deaths and 180 injuries
Lessons learned include the importance of process safety culture, effective management of change, and learning from previous incidents
Deepwater Horizon Oil Spill (2010) a massive oil spill in the Gulf of Mexico resulting from the explosion and sinking of the Deepwater Horizon drilling rig
Lessons learned include the importance of effective risk assessment, emergency response planning, and regulatory oversight
Fukushima Daiichi Nuclear Disaster (2011) a series of equipment failures, nuclear meltdowns, and releases of radioactive materials at the Fukushima Daiichi Nuclear Power Plant in Japan following a severe earthquake and tsunami
Lessons learned include the importance of designing for extreme events, effective emergency response, and transparent communication
West Fertilizer Company Explosion (2013) a massive explosion at a fertilizer storage and distribution facility in West, Texas, resulting in 15 deaths and more than 160 injuries
Lessons learned include the importance of community planning, emergency response coordination, and the safe storage of hazardous materials
Chevron Richmond Refinery Fire (2012) a fire at a Chevron refinery in Richmond, California, caused by a corroded pipe, resulting in a large plume of smoke and thousands of residents seeking medical attention
Lessons learned include the importance of effective mechanical integrity programs, incident investigation, and community outreach
DuPont La Porte Facility Toxic Chemical Release (2014) a toxic chemical release at a DuPont chemical plant in La Porte, Texas, resulting in four employee fatalities
Lessons learned include the importance of effective process safety management, emergency response planning, and the use of inherently safer design principles