CASE HISTORY

The study of case histories is important in the area of safety. To paraphrase G. Santayana, one learns from history or is doomed to repeat it. This is especially true for safety anyone working in the chemical industry can learn from case histories and avoid hazardous situations or ignore history and be involved in potentially life-threatening accidents. 

In this chapter we cover case histories as reported in the literature. References are provided for more thorough studies. The objective of this chapter is to illustrate, through actual case histories, the importance of applying the fundamentals of chemical process safety. 

These case histories are categorized into four sections  

The cause of a specific accident frequently places it in more than one category. Each of these sections includes descriptions of several accidents and a summary of the lessons learned. 

The following statements place the case histories into perspective  

The following sections will focus on two case histories from our own activities in the field that exemplify the key challenges and the way they may be addressed in practice. First, the focus will be on a new class of titanium hydrazinediido halfsandwich complexes, which have displayed remarkable activity in the hydrohy-chazination of terminal alkynes and of carbodiimides. This will be followed by the presentation of a catalytic cascade of N - N and C - H scissions and C - C and C - N coupling steps in the coordination sphere of zirconium, which directly converts alkynes and hydrazines to indoles along a non-Fischer-type reaction pathway. 

Highly Active Titanium Catalysts for the Hydrohydrazination of Terminal Alkynes and Aminoguanylation of Carbodllmides 

While the catalytic amination of carbodiimides ( guanylation ) has been explored for many transition-metal, lanthanide, and even group 1 and 2 complexes as catalysts [21], there was only one previous example of catalytic aminoguanylation employing alkylaluminum precatalysts, reported by Koller and Bergman in 2010 [22]. 

Now that we have discussed some details of HAZWOPER, let s review some case histories to see how we can put this in perspective. Case histories are important because they can be used as learning tools. 

If a truck driver is hauling clay fill into an exclusion zone, does this fall under the HAZWOPER standard At some sites, it might be a requirement that ALL persons (including truck drivers) are HAZWOPER trained. However, in all likelihood, a requirement to HAZWOPER train all truck drivers would be a difficult requirement to administer. At most sites, drivers are not HAZWOPER trained. One way to avoid this training would be to require that the drivers do not drive through contaminated areas. In addition, make sure that the drivers know that they must not leave their trucks and that they should keep their windows rolled up. 

Keep in mind that we are not reeommending that your drivers should not be trained. On the eontrary, if it is reasonable to train the drivers, it is an exeellent idea. However, the truek driver population often is transient by nature. After you have invested time and money to train a driver it ean be diflfieult to ensure that you will be able to reap the benefits from this training. Drivers ean be dispatehed to a variety of plaees for a variety of reasons. Keeping this in mind, it makes sense to manage so that the drivers would not be required to be HAZWOPER trained. 

Case 2 Utility Workers Servicing Electrical Equipment 

Wlien utility work is located in an exclusion zone, are workers who enter the area exposed to hazardous materials Hazard characterization and exposure assessment performed by a competent person may show that the area surrounding the equipment and an access corridor leading to the equipment can be cleaned so that the utility workers can work in the 

Military weapons tests conducted at the Pacific Proving Grounds in the 1940s and 1950s resulted in greatly elevated local 

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This case history presents only a simple account of one of R.B. Woodward s adventures based on ingenious undentanding of structural features and experimental findings described in the literature. The hydrogenation of porphyrins is still one of the most active subjects in heterocyclic natural products chemistry, and the interested reader may find some modem developments in the publications of A. Eschenmoser (C.Angst, 1980 J.E. Johansen, 1980). 

Japan s Chlor—Alkali Producers Save Energy by Retrofiting Diaphragm Cells (Case History), E. I. du Pont de Nemours Co., Inc., Wilmington, Del. 

S-100 Activated Alumina for Claus Catalysis, Case Histories, Alcoa Chemicals Division, Aluminum Company of America, Pittsburgh, Pa., 1985. 

Another way to determine durabHity is to find successfuHy sealed, existing field instaHations. Sealant manufacturers often have case histories of successful instaHations. Adhesion performance can vary widely with sealant type, substrate type, and cleaning method. Eor this reason, it is important to understand the sealant s sensitivity to cleaning practices. Often with difficult-to-adhere substrates, a primer is used. Sealant manufacturers can provide recommendations as to which substrates require primers, what type of primers should be used, and how they should be appHed. 

Nonstirred ARC runs may give answers that do not adequately duphcate plant results when there are reactants that may settle out or that require mixing for the reaction to be carried out (DeHaven and Dietsche, The Dow Chemical Company, Pittsburgh, Calif., Catalyst Explosion A Case History, Plant (Operations Progress, April 1990). 

Personnel Hazards The following case history illustrates how vacuum can be harmful and dangerous to personnel. A plant superintendent was checkiug an open nozzle on a glass-lined reactor on which there was a vacuum pump pulling vacuum, when suddenly his arm was sucked into the nozzle, up to his shoulder. He could not remove his arm until help arrived to release the vacuum on the vessel. He was injured painfully, though not seriously. The injury could have been veiy serious if help had not been nearby. Personnel hazards can also result from vacuum conveyor systems for solids handling. 

Case Histories Following are examples of fatal accidents resulting from lack of oxygen ... 

Shells, clams, wood fragments, and other biological materials can also produce concentration cell corrosion. Additionally, fragments can lodge in heat exchanger inlets, locally increasing turbulence and erosion-corrosion. If deposits are massive, turbulence, air separation, and associated erosion-corrosion can occur downstream (see Case History 11.5). 

Small organisms frequently become embedded within corrosion products and deposits. The organisms may make up a sizable fraction of the deposit and corrosion product. Seed hairs and other small fibers often blow into cooling towers, where they are transported into heat exchangers. The fibers stick to surfaces, acting like sieves by straining particulate matter from the water. Deposit mounds form, reinforced by the fibers (see Case History 11.5). 

Figure 6.10 A perforated carbon steel pipe at a weld-backing ring. The gaping pit was caused by sulfate-reducing bacteria (see Case History 6.1).

TABLE 6.6 Microbiological Evaluations of Water and Deposits in Case History 6.1 ... 

After only 4 months of service, the main condenser at a large fossil utility began to perforate. Initial perforations were due to erosion-corrosion (see Case History 11.5). Small clumps of seed hairs entering the condenser after being blown into the cooling tower were caught on surfaces. The entrapped seed hairs acted as sieves, filtering out small silt and sand particles to form lumps of deposit (Fig. 6.24A and B). Immediately downstream from each deposit mound, an erosion-corrosion pit was found. 

This case history illustrates the paradox so often encountered in microbiologically influenced corrosion. Clearly, two corrosion mechanisms were operating in the system, namely, acid attack and microbiologically influenced corrosion. To what degree each mechanism contributed to wastage is difficult to quantify after the fact. This was especially the case here, since other areas of the rolling oil system were attacked by a predominantly acidic form of corrosion. 

TABLE 6.7 Microbiological Evaluation of Material Removed from Corroded Areas in Case History 6.7 ... 

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