Process safety management of hazardous chemicals

Tragedies such as the explosion at a Texas Phillips petroleum company plant in 1989 prompted the U.S. Department of Labor Occupational Safety and Health Administration (OSHA) to initiate Process Safety Management1, and eventually issue 29 CFR 1910.119, Process Safety Management of Highly Hazardous Chemicals, in 1992.

Chemicals identified to be highly hazardous have the potential to be catastrophic when released unexpectedly. OSHA defines a highly hazardous chemical as a substance that is both toxic and reactive such as anhydrous ammonia, chlorine, phosphine, sulfur dioxide and more. Process safety management works to ensure proper controls are put in place to manage process hazards, outlining a comprehensive program to manage risk and avoid disaster.

All companies — big and small — required to comply with OHSA’s Process Safety Management (PSM) are likely mandated to also comply with Risk Management Plan (RMP), an overlapping regulation the U.S. Environmental Protection Agency (EPA)2 issued around the same time that OSHA established PSM. Although issued by different agencies, RMP and PSM are both working toward the same goal — preventing the accidental release of hazardous substances — but each has its own focus.

As their namesakes imply, OSHA is focused on protecting workers, and the EPA program is geared to protecting the environment and the community. The information in an RMP closely mirrors the process safety plan; each facility’s program must address hazard assessment details, prevention programs and an emergency response program. Unlike an employer’s PSM program, RMPs are accessible to the public including local fire, police and emergency response personnel. This way, they can adequately prepare to respond to an unintentional chemical spill.

Process safety information

Before conducting any process hazard analysis, employers are required to compile complete and accurate process safety information. Gathering this data helps employers and employees better understand and identify hazards posed by processes.

The three facets to process safety information3 include the following:

Information pertaining to hazards of the highly hazardous chemicals (HHCs) used or produced by the process: At the minimum, this information must include toxicity information, permissible exposure limits (PELs), physical data, reactivity data, corrosivity data, thermal and chemical stability data, and risks of inadvertent mixing (1910.119(d)(1)). Safety data sheets can be a great reference when gathering this information.

Information pertaining to the technology of the process: In addition to a diagram of the process, either a block flow diagram or a simplified process flow diagram, information on the technology must also include (at the very least) process chemistry, maximum intended inventory, safe upper and lower limits for temperatures, flows, compositions, pressures, etc., and an evaluation of the consequences of deviations — what will happen and what is the likelihood? If this technical information no longer exists, it can be developed in sufficient detail in conjunction with the process hazard analysis. 

Information pertaining to the equipment in the process: This includes materials of constructions, piping and instrument diagrams (P&IDs), electrical classification, relief system design and design basis, ventilation system design, design codes and standards employed, material and energy balances for processes, and any safety systems such as interlocks or detection system. It must be documented that equipment complies with recognized and generally accepted good engineering practices.

The data collected is central to the entire process safety program; it will be used to conduct thorough hazard analyses, develop standard operating procedures, select control measures, and evaluate the effectiveness of any changes within the process. Furthermore, this information should be accessible to all workers.

Hazard recognition: Process hazard analysis

Process hazard analysis, noted as the key provision of PSM1, is a detailed and systematic method to identifying the hazards associated with a process, evaluating the risks and implementing control measures. Analyses are conducted by a team made up of engineers, process operations experts and employees experienced with the process being evaluated.

How an analysis is performed is dependent on the complexity of the process. Employers must choose one or more of the OSHA-suggested analysis methods: what-if, checklist, hazard and operability study (HAZOP), failure mode and effects analysis (FMEA), or fault tree analysis. Regardless of the method selected, a process hazard analysis must address the following:

• The hazards of the process
• Any previous incidents with potentially catastrophic consequences
• Applicable engineering and administrative controls
• Consequences resulting from failure of engineering and administrative controls
• Facility siting
• Human factors
• Thorough evaluation of safety and health effects on employees in the case of failure of controls

OSHA recommends one of the members on the team conducting the process hazard analysis (PHA) be knowledgeable in the specific analysis methods being used.

Compliance

Collecting process safety information and conducting a process hazard analysis are only two components of compliance. In total, OSHA has defined 14 interdependent elements of a PSM program. When an OSHA inspector comes in to review the program, they will be looking for written documentation on the following:

• Compliance audits: Safety audits must be conducted and reported periodically.
• Training: Employees must be trained on hazards and procedures.
• Contractors: Any contractors working on or near HHCs must be trained on emergency procedures and other applicable PSM program elements.
• Hot work: Hot work permits must be issued and procedures established before anyone can conduct hot work operations on or near a covered process.
• Mechanical integrity: Process equipment, including pressure vessels, storage tanks, piping systems, system controls, emergency shutdown systems, etc., must be periodically inspected, and employers will need to establish written procedures for maintenance.
• Operating procedures: Employers must develop and implement safe procedures for the initial startup, procedures for temporary operations, emergency shutdown procedures or any other activities involved with the covered process.
• Incident investigation: For every single incident which resulted in — or could have reasonably resulted in — a catastrophic release of HHCs in the workplaces, these investigations must be promptly initiated.
• Management of change: For any changes to process chemicals, technology, equipment, procedures or to the facility that affects a covered process, employers must evaluate potential hazards and establish written procedures for managing those changes.
• Employee participation: Employers are required to involve all employees, including production staff and maintenance workers, in PSM programs.
• Trade secrets: Regardless of possible trade secret status, employers are mandated to provide employees with all information required by PSM.
• Pre-startup safety review (PSSR): Employers must conduct PSSRs⁴ before any new or modified equipment can be operated.  
• Emergency planning and response: An emergency action plan for the entire facility must be established and documented. It must include safety procedures for handling small releases of hazardous chemicals.

Each of these elements are necessary in creating a complete, comprehensive process safety management program. Along with EPA's Risk Management Plan, process safety management ensures the safety of workers, protects the environment and helps prevent future catastrophes. 

References

1. Occupational Safety and Health Administration (OSHA). OSHA 3132, Process Safety Management. https://www.osha.gov/Publications/osha3132.html.
2. Environmental Protection Agency, Risk Management Plan (RMP) Rule Overview. https://www.epa.gov/rmp/risk-management-plan-rmp-rule-overview.
3. Occupational Safety and Health Administration, 1910.119 - Process safety management of highly hazardous chemicals. https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.119.
4. Occupational Safety and Health Administration (OSHA). OSHA 3133, Process Safety Management Guidelines for Compliance. https://www.osha.gov/Publications/osha3133.html.