SAFETY BY CONTROL

The integrity of pipelines depends upon conect design, including materials selection, support and protection from mechanical damage. Depending upon tlie gas, routine inspection and maintenance may be supplemented by the provision of gas detection and alarm systems. Other considerations are exemplified by the safety-related controls on the transportation of domestic gas via pipeline systems summarized in Table 15.17. 

We put a lot of effort into improving safety by adding protective equipment onto our plants, new and old gas detectors, emergency isolation valves, interlocks, steam curtains, fire insulation, catchment pits for LPG storage tanks, and so on. We also introduced new procedures, such as hazard and operability studies and modification control, or persuaded people to follow old ones, such as permits-to-work and audits. 

Human Factors Engineering/Ergonomics approach (control of error by design, audit, and feedback of operational experience) Occupational/process safety Manual/control operations Routine operation Task analysis Job design Workplace design Interface design Physical environment evaluation Workload analysis Infrequent... 

In this context, Benson and Ponton declare that while the chemical industry has made considerable achievements in reactor performance, safety and control, comparable to those in the microelectronics business, this success is by no means evident to the public, in deep contrast to the latter [139], It is said that this is mainly and in a way simply due to the visual recognition of chemical production plants. From a distance and for somebody outside the field, the chemical plants of the late 1940s and the early 1990s look virtually similar, whereas one is able immediately to see the big differences in, e.g., television sets and automobiles. Hence it is not evident that notable improvements were made over the decades. 

The need under each heading is to decide what data are required, then how to obtain them with the greatest efficiency and economy, and last, whether the toxicologist is necessarily the person with the appropriate skills and experimental techniques to do so. There will often be a trade-off between precise control by other means and possibly cheaper or more familiar, old-fashioned toxicological studies. The inventor of a new product or process, too, may often have to do a great deal of work to show safety by excluding hypothetical hazards, which subsequent manufacturers can afford to ignore. 

The concept of a safety case comes from the requirements of the European Union/European Community (EU/EC) Seveso Directive (82/501/EC) and, in particular, regulations that the United Kingdom and other member states used to implement that directive. United Kingdom regulations (Control of Industrial Major Accident Hazards [CIMAH], 1984 replaced by Control of Major Accident Hazards Involving Dangerous Substances [COMAH] in 1999) require that major hazardous facilities produce a safety report or safety case.64 The requirement for a safety case is initiated by a list of chemicals and a class of flammables. Like the hazard analysis approach (Section 8.1.2), experts identify the reactive hazards of the process if analysis shows that the proposed process is safe, it may be excluded from additional regulatory requirements. 

Isolation or emergency shutdown (ESD) valves should be installed to stop fuel flow and the process feed flow into the heater in the event of heater tube rupture. These valves can be automatically actuated by controls or safety interlocks or can be manually operated remotely. Remote actuation can be from a control room console or in the field field actuation stations should be located at least 50 ft (15 m) from the heater. It is also common to provide a manual block valve, located at least 50 ft (15 m) from the heater, on each of the fuel and process feed lines. These should be accessible to operators in the event of an incident involving the heater. 

A great deal can and should be said about safety, but we have only been able to outline the principles by which chemical reactors may go out of control. We will conclude our discussion of safety by listing some of the notorious accidents that have occurred in the chemical industry. 

The responsibility of chemical process managers for preventing air, water, and soil pollution has indirectly influenced plant safety by requiring better control of plant processes to prevent releases of hazardous materials. Regulatory legislation was introduced by the Health, Education, and Welfare Department (Health and Human Services) and the U.S. Environmental Protection Agency (EPA) to require (/) improvements in air quality (1955 Air Pollution Act ... 

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