An Introduction to Chemical Process Safety

This chapter is from the book

Chemical Process Safety: Fundamentals with Applications, 4th Edition

Learn More Buy

This chapter is from the book

This chapter is from the book 

Chemical Process Safety: Fundamentals with Applications, 4th Edition

Learn More Buy

Safety is a common denominator across all aspects of life; hence knowledge should always be shared. It is not a matter for industry—it is a matter for humanity.

—Doug Bourne

We believe that the traits required to achieve excellence in safety are the same as those required to achieve outstanding results in all other aspects of our business.

—Ralph Herbert, Vice President of Engineering, ExxonMobil

The learning objectives for this chapter are:

1. Understand the common definitions used for process safety.

2. Explore myths about process safety.

3. Identify components of a safety culture.

4. Discuss individual risk, societal risk, and risk populations.

5. Distinguish between voluntary risk and involuntary risk.

6. Describe safety metrics.

7. Summarize accident and loss statistics.

8. Create a risk tolerance/acceptance and risk matrix.

9. Discuss codes, standards, and regulations related to process safety.

10. Explore safeguards related to chemical process safety.

11. Explain risk-based process safety (RBPS).

12. Describe inherently safer design.

13. Describe the Bhopal, India, tragedy.

The Aluminum Company of America—otherwise known as Alcoa—was founded in 1888 by Charles Martin, who discovered an affordable way to produce aluminum via electrolysis. The company is headquartered in Pittsburgh, Pennsylvania. In 1889, Alcoa developed the first aluminum tea kettle; in 1910, it introduced aluminum foil. Today, Alcoa is the largest supplier of aluminum in the world.

In 1987, however, Alcoa was faltering. Its revenues and profits had fallen, several product lines had failed, and the company had large inventories of unsold product. Many investors considered Alcoa to be a “Rust Belt” company, associating it with the failing steel companies located in Pittsburgh and elsewhere in the United States. In addition, both the employees and unions were unhappy with the company.

As is the case with most companies facing this kind of situation, Alcoa’s board of directors decided to hire a new chief executive officer (CEO). They tapped Paul O’Neill, formerly of International Paper, to lead the company.

In October 1987, O’Neill held his first press conference in a swanky hotel in Manhattan, attended by members of the media, investors, and investment managers. All attendees expected O’Neill to announce a new financial management strategy for the company. Instead, O’Neill came to the podium and said, “I want to talk to you about worker safety. I intend to make Alcoa the safest company in America. I intend to go to zero injuries.” At this time, Alcoa already had an industry leading safety program.

One investment manager ran out of the press conference declaring, “The board put a crazy hippie in charge and he’s going to kill the company! I called my clients and told them to sell their stock!”

But six months later, a tragedy occurred. A young employee in an Arizona plant jumped over a yellow safety wall to repair a piece of equipment and was crushed when the equipment was unexpectedly activated. O’Neill immediately called an emergency meeting of the plant’s executives. He stated bluntly: “We killed this man. It’s my failure of leadership. I caused his death. And it’s the failure of all of you in the chain of command.”

O’Neill sent a note to all workers telling them to call him at home if managers didn’t follow up on safety suggestions. He received lots of calls about safety, but he also heard a lot of suggestions for other improvements—many of which would substantially reduce costs.

What were the results of O’Neill’s safety leadership? In 1986, Alcoa recorded $264 million in net income on sales of $4.6 billion. When O’Neill retired at the end of 2000, Alcoa boasted record profits of $1.5 billion on sales of $22.9 billion. Alcoa’s lost work days rate per 100 employees dropped from 1.86 to 0.2 by the end of O’Neill’s tenure. In March 2016, that rate was a mere 0.055.

When asked later about the secret to his success, O’Neill stated, “I knew I had to transform Alcoa. But you can’t order people to change. So I decided I was going to start by focusing on one thing. If I could start disrupting the habits around one thing, it would spread throughout the entire company.” O’Neill’s important realization was that safety performance and economic performance were, in his words, “glued together”—with outstanding safety performance resulting in outstanding economic performance. When O’Neill started at Alcoa, he wasn’t sure if this approach would work perfectly, but it did.

Safety, in general, is defined as “a strategy for accident prevention.” Process safety is safety applied to processes, including chemical processes. Table 1-1 provides a more complete definition of process safety, along with several important definitions provided by the American Institute for Chemical Engineers (AICHE) Center for Chemical Process Safety (CCPS). Another common term used in the safety realm is loss prevention, which is defined as the prevention of incidents that cause losses due to death, injury, damage to the environment, or even loss of production or inventory.

Table 1-1 AICHE Center for Chemical Process Safety Definitions Related to Process Safety

Source: Adapted from AICHE/CCPS online glossary. https://www.aiche.org/ccps/resources/glossary. Accessed July 2018; and AICHE/CCPS, Guidelines for Chemical Process Quantitative Risk Analysis, 2nd ed. (New York, NY: American Institute for Chemical Engineers, 2000).

A hazard, in general, is anything that can cause an accident. Table 1-1 provides a more precise definition for a hazard that is more suitable for process safety usage. Hazards can arise due to materials, energy, physical situations, equipment design, and even procedures. In addition, hazards may be continuously present or intermittent. For instance, electricity in a room represents a continuous hazard to the room occupants. An electrical cord run across the floor of a lecture hall is also a physical tripping hazard that may not be present all the time. Note that something needs to occur for the hazard to result in an accident.

An accident is, in general, an undesirable consequence that occurs with an activity. A process safety incident has a more specific definition, being limited to an accident that occurs in a process or, more specifically, in a chemical plant. It includes undesirable outcomes, such as harm to people, damage to the environment, or asset/business losses. In general, a chemical plant incident is caused by loss of containment of chemicals or control or material or energy. An example of an incident would be a leak of ammonia from the connecting pipeline to a pressurized ammonia tank.

Typical hazards that occur in chemical plants include chemicals that are toxic, flammable, or reactive; high and low pressures and temperatures; and hazards due to the process design, maintenance, operations, control, and many other factors. An example of a hazard would be a pressurized tank containing 1000 kg of ammonia.

Hazard analysis/evaluation includes the identification of the hazard as well as the determination of how that hazard could result in a consequence. An example of a hazard analysis would be the identification of ammonia in a pressurized tank as a hazard and the identification of a leak in the connecting pipe due to corrosion as a possible incident. Estimation of the downwind airborne concentrations of ammonia would provide information on the consequences of such an incident.

The more information and knowledge one has about a process, the more thorough and valuable the hazard analysis/evaluation will be. Key process information required for chemical plant hazard analysis/evaluation includes the following items:

1. Chemical-related properties, including hazardous properties, physical properties, and more

2. Process conditions, including temperature and pressure, flow rates, concentrations, and other factors

3. Equipment design parameters, including equipment capacity, operating limits for temperature and pressure, materials of construction, and pipe wall thicknesses, among others

4. Site and plant layout, including equipment spacing, control room location, and other considerations

5. Procedures and policies, including startup, operating, shutdown, maintenance procedures, and others

6. Location and nature of adjacent communities and sensitive locations, such as schools

Other information might also be important depending on the particular process. The quality of any hazard analysis/evaluation is directly related to the quality of the information available to the analysis team.

Risk is another important definition in the process safety arena. Risk is a function of both likelihood and consequence, where likelihood considers either probability or frequency. It is essential to include both likelihood and consequence in the assessment of risk. As an example, consider the risk assessment for seat belt usage in automobiles. Many people argue against seat belt usage by noting that the likelihood of an accident is small—many people drive their entire lifetime without ever having an accident. However, seat belts are worn entirely to reduce the consequences of an accident and have no effect on the likelihood.

Risk analysis involves a more detailed mathematical analysis to combine the consequences and likelihood from multiple hazards. By comparison, risk assessment involves the evaluation of the risk analysis so as to make decisions—for example, decisions about which chemicals to use, the design of the plant, materials of construction, operating conditions, and so on.

1-1 Engineering Ethics

The AICHE expects all of its members, including student members, to exhibit professional conduct, as defined in its Code of Ethics for Engineers from the National Society of Professional Engineers. Every AICHE applicant must attest to knowledge of the Code of Ethics and willingness to comply with it when signing his or her membership application. As shown in Table 1-2, the first item in the Code of Ethics states that the “safety, health, and welfare of the public” must be held “paramount in the performance of their professional duties.” Item 2 is also related to process safety—chemical engineers have a responsibility to report activities that will “adversely affect the present and future health or safety of their colleagues and the public.” Engineers have a responsibility to themselves, fellow workers, family, community, and the engineering profession.

Table 1-2 American Institute of Chemical Engineers’ Code of Professional Ethics

Approved by the AICHE Board in November 2015.