PROCESS INVESTIGATIONS

Different investigators use different approaches to accident investigations. One approach that can be used for most accidents is described here and shown in Table 12-2 it is an adaptation of a process recommended by A. D. Craven.2 

2Howard H. Fawcett and William S. Wood, eds., Safety and Accident Prevention in Chemical Operations (New York Wiley, 1982), pp. 659-680. 

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Any set of guidelines must be tempered by the analysts experience. This is an investigative process. The explanations are rarely simple. However, many exhaustive tests have been run to identify that a bypass valve or alternative feed valve had been mistakenly left open. Plant resources were misused because the simple was overlooked ... 

The final incident investigation report written by the assigned incident investigation team (which may include members from the client) can be written in a less structured way depending on the extent of the incident. A detailed discussion of how and why to conduct incident investigations can be found in the AIChE publication. Guidelines for Investigating Process Safety Incidents, Second Edition. 

Many lAQ problems are simple to resolve when facility staff have been educated about the investigation process. In other cases, however, a time comes when outside assistance is needed. Professional help might be necessary or desirable in the following situations, as examples ... 

Employees in the process area where the incident occurred should be consulted, interviewed, or made members of the team. Their knowledge of the events represents a significant set of facts about the incident that occurred. The report, its findings, and recommendations should be shared with those who can benefit from the information. The cooperation of employees is essential to an effective incident investigation. The focus of the investigation should be to obtain facts, and not to place blame. The team and the investigative process should clearly deal with all involved individuals in a fair, open, and consistent manner. 

Typically, the first phase of a comprehensive accident investigation process will involve describing the way in which the hardware, the chemical process, individual operators and operating teams are involved in the accident process. This is the domain of the structural analysis techniques and the technical analysis of the chemical process which gave rise to the accident. Analyses of human error will primarily address the interactions between hardware systems and individuals or operating teams (the first two layers... 

However, MORT does not aid in the representation of the accident sequence which must first be determined before the method can be effectively used. Although MORT provides a comprehensive set of factors which may be considered when investigating an incident, it can easily turn an investigation into a safety program review as no guidance is provided on the initial investigative process. 

The STEP procedure, described by Hendrick and Benner (1987), was developed from a research program on incident investigation methods. STEP is based on the mulHple events sequence method and is an investigative process which structures data collection, representation, and analysis. 

Planned changes should be documented as part of a formal change monitoring process (for example via a quality assurance system). Unplanned changes should be identified during the accident investigation process. 

Incorporation of psychological models of human error into the investigation process... 

Paradies, M., Unger, L., Ramey-Smith, A. (1992). Development and TesHng of the NRC s Human Performance Investigation Process (HPIP). In Proceedings of the International Conference on Hazard Identification and Risk Analysis, Human Factors and Human Reliability in Process Safety, New York American Institute of Chemical Engineers, Center for Chemical Process Safety. Pp. 253-260. 

The formation and stability of peroxoniobates and peroxotantalates can be used successfully in the technology of tantalum and niobium oxide production. Belov, Avdonina and Mikhlin [512] investigated processes of precipitation and thermal decomposition of high-purity ammonium tetraperoxoniobate and tetraperoxotantalate as precursors for the production of tantalum and niobium... 

In another investigation, process development and optimization studies were undertaken [67]. In the framework of a study conducted as contract research for... 

FIG. 7 Reaction scheme between CgH50Na and DPPC in the water-nitrobenzene system. The part surrounded by the dashed line is the investigated process. 

Notably, with a single set of rate parameter estimates, the present model can also correctly describe the effects of all the investigated process conditions on product distribution. Figure 16.10 compares experimental and calculated ASF product distributions in five of the investigated process conditions. It is worth noticing also that the model predicts the hydrocarbons selectivity up to n = 49,... 

To fully utilize this layered technique, the investigation process is conducted with an open mind. Facts about the accident that support conclusions at all three levels are accumulated. 

Illustrate the layered investigation process to develop underlying causes of a municipal pool accident. 

Using the layered accident investigation process discussed in chapter 12, develop the underlying... 

Illustrate the layered accident investigation process, using Example 13-1 as a guide, to develop the underlying causes of the duct system explosion described in section 13-1. 13-2. Repeat Problem 13-1 for the bottle of isopropyl ether accident described in section 13-2. 13-3. Repeat Problem 13-1 for the nitrobenzene sulfonic acid decomposition accident described in section 13-2. 

Identifying causes is one of the primary objectives of the entire investigation process. Initial selection of the root cause determination process will most likely require some special attention to the concepts of multiple causes (especially when dealing with reactive chemistry) and to underlying system-related causes. 

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