Abstract
This knol provides an overview of the topic of Process Safety Management (PSM).
Introduction
The goal of a Process Safety Management (PSM) program is to ensure that process facilities such as chemical plants, oil refineries, gas plants and offshore platforms are operate safely. PSM programs focus on major process-related events such as fires, explosions and the release of toxic chemicals.
The nature of Process Safety Management (PSM) can be understood by examining its component words.
- The first word is Process. PSM is concerned with process issues such as fires, explosions and the release of toxic gases casused by process-oriented issues such as runaway chemical reactions, corrosion and the inadvertent mixing of hazardous chemicals
- The second word in the term PSM is Safety. The initial driving force for most PSM programs was the need to meet a safety regulation, and to reduce safety incidents related to process upsets and hazardous materials releases. Increasingly, however, the managers of process facilities are using their PSM programs as part of their Operational Integrity and Excellence programs, as illustrated in Figure 1.
- The third word is Management. In this context a manager is taken to be anyone who has some degree of control over the process, including operators, engineers and maintenance workers. Use of the word management also means that PSM is not just about equipment and instrumentation, but also covers issues such as Employee Participation, Operating Procedures and Management of Change.
Figure 1
From Process Safety to Operational Integrity
Types of Safety
- Technical safety;
- Process safety; and
- Occupational Safety
Technical Safety
Technical safety focuses on engineering and design decisions, and so is best applied during the early stages of a design. It is concerned with items such as:
- Gas dispersion
- Blast analysis
- The design of temporary refuges
The term Formal Safety Assessment (FSA) is sometimes used to cover technical safety issues.
Process Safety
As already noted, Process Safety is focused on process-related events that have high consequences.
The Center for Chemical Process Safety provides guidance as to what constitutes a PSM event:
- It must involve a chemical or have chemical process involvement;
- It must be above a minimum reporting threshold;
- It must occur at a process location; and
- The release must be acute, i.e., it must occur over a short period of time.
Occupational Safety
It is particularly crucial to distinguish between process safety and occupational safety. The “Baker Panel report“ that was written following the explosion at BP’s Texas City refinery in 2005 stated,
The distinction between occupational and process safety means that safety triangles, such as that shown in Figure 2, should be used with care. The basic idea behind the use of such triangles is that major events such as fatalities, large environmental spills and serious financial losses occur only rarely. By contrast, near misses and low consequence events are much more common and can be seen as being precursors to the more serious events. Using the ratios shown in the sketch, it is assumed that if a facility can move from 10000 to 9000 near misses, then the number of fatalities will be reduced from 10 to 9, and the chance of a catastrophe will also go down by 10%. However, fatal and catastrophic events are often caused by process safety deficiencies. Therefore improvements in occupational safety that reduce the number of low consequence events may not reduce the chance of a major accident, and may even lead to a false sense of complacency.
The Safety Triangle
Regulations and Standards
The first onshore PSM regulations were developed in response to a number of serious accidents that occurred in the 1980s, such as the release of toxic vapors at Bhopal, India that killed thousands. In the United States the federal regulation 29 CFR 1910.119 Process safety management of highly hazardous chemicals was published in the year 1992 by the Occupational Safety & Health Administration (OSHA). In 1996 the Environmental Protection Agency (EPA) established its Risk Management Program (last updated 2004) which includes the environment and public safety within the scope of PSM. In addition, some states brought out their own PSM rules. These include:
- New Jersey’s Toxic Catastrophe Prevention Act (1986);
- Delaware’s Extremely Hazardous Substances Risk Management Act (1989); and
- Nevada’s Chemical Accident Prevention Program (CAPP).
Various professional societies have also created standards and guidance for Process Safety Management programs. An example is the American Petroleum Institute (API) Recommended Practice 750 Management of Process Hazards.
Elements of PSM
Process Safety Management programs are typically divided into a set of between twelve and twenty inter-related elements. The list below is from the OSHA reference provided above
The elements link with one another. For example, an engineer may wish to change operating conditions. First she must find out what the current operating limits are (element 2). The proposed change will then be put through the Management of Change system (element 10); which may require that a HAZOP be performed (element 3); then operating information (element 2), operating procedures (element 4) and training programs (element 5) must be updated. Before making changing conditions in the field a Prestartup Safety Review (element 7) needs to be performed. Finally the updated program must be audited (element 13).
Features of Process Safety Management
Participation
PSM is not a management program that is handed down by management to their employees and contract workers; it is a program involving everyone. The key word is participation — which is much more than just communication. All managers, employees and contract workers are responsible for the successful implementation of PSM. Management must organize and lead the initial effort, but the employees must be fully involved in its implementation and improvement because they are the people who know the most about how a process really operates, and they are the ones who have to implement recommendations and changes. Specialist groups, such as staff organizations and consultants can provide help in specific areas, but PSM is fundamentally a line responsibility.
On-Going
Non-Prescriptive
Process safety management programs are non-prescriptive which means that the regulations and other standards in this field generally provide very little detail as to what needs to be done. For example, the technical section of the OSHA PSM standard is only about ten pages long.
Basically, PSM rules say ‘do whatever it takes on your facility not to have accidents’. It is up to the managers and employees to determine how this should be done. There are no universally ‘correct answers’ as to what needs to be done to achieve a safe operation. What is appropriate in one location may or may not be appropriate in another. The PSM standards simply require that programs be in place, and that they be adhered to. (In this regard, PSM is similar to ISO 9000 and other quality standards, which also require that companies set their own standards, and then adhere to them.)
Performance-Based
Programs that are non-prescriptive are, of necessity, performance-based. This means that the only true measure of success is not to have upsets or accidents. Consequently, from a theoretical point of view, it is impossible to achieve ‘compliance’. The only truly acceptable level of safety is zero accidents. Yet, no matter how well run a facility may be a zero accident rate is a theoretically unattainable goal. In spite of the fact that many companies set a target goal of ‘zero accidents’, risk can never be zero, and accidents can always happen. Indeed, if a unit operates for long enough, it is certain - statistically speaking - that there will be an accident. Hence, even though the stated PSM goal may be ‘zero accidents’, in practice, management has to determine a level for ‘acceptable safety’ and for realistic goals.
