Physical barrier analysis

Physical Barrier Analysis (PBA) is based on four assumptions  

There are four types of physical barriers. When a physical intervention can prevent an accident, that intervention will always be one, or a combination, of the four types of physical barriers. 

Accidents not caused by the lack of a physical barrier cannot be prevented by introducing such a barrier. 

Being able to identify accidents that a physical barrier could have prevented and those that a physical barrier could not have prevented allows the analyst to fit ranedies to the causes of accidents more accurately. 

Acddaits related to physical barriers are almost always the easiest type to prevent 

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These four assumptions place physical barriers in proper perspective. While stressing their importance, their limitations are also dehned. In order to perform a physical barrier analysis, the following will be needed ... 

Using the company s accident investigation forms, the first thing to do in analyzing the accident is to read the narrative and visualize what happened. Often, the report is sketchy, but most of the time you will be able to draw on your experience to read between the lines and get the picture. Once you have visualized the situation and what occurred, then ask What could have prevented this accident To help determine the appropriate preventive measures, make use of the list of physical barrier analysis statements. The following statements refer to each of the four types of physical barriers. For each type, there are four possibilities. Select the one that best represents a valid opinion of the accident. 

The PBA matrix is simply the PBA statements in a different format. Normally, many accidents will be analyzed. When this occurs, the accidents are numbered so that choices for each accident will equal four. If the example was accident number 1, then (1) would be placed in the appropriate cells corresponding to the selections that were made. In this example, a (1) would be placed in cells lA, 2A, 3C, and 4A. This now completes the Physical Barrier Analysis of one accident. A listing of the steps for a PBA that is normally followed is ... 

MSHA s 1988 Coal Accident Analysis and Problem Identification Instruction Guide shows how a system of classification designed to collect premium data can become an artificial template that structures not only the activity of the inspection but also the conclusions that inspectors can draw from their data. The Instruction Guide provides a set of checklists, tally sheets, and planned inquiry sheets to help inspectors categorize accidents. The classification system in the Physical Barrier Analysis Matrix (Fig. 3.1) seems to support the conclusion that physical barriers are either not possible or practical in most of the cases reported on the form—a conclusion that might exempt management from responsibility for protecting workers. Because data from such an analysis directly affects policy and procedures, classification systems can have... 

FIG. 3.1. The Physical Barrier Analysis Matrix. This document seems constructed to. support the conclusion that physical barriers are not possible or practical in most of the cases reported on the form. Source U.S. Department of Labor, Mine Safety and Health Administration (1988a, p. 63). 

The design of most process plants relies on redundant safety features or layers of protection, such that multiple layers must fail before a serious incident occurs. Barrier analysis ) (also called Hazard-Barrier-Target Analysis, HBTA) can assist the identification of causal factors by identifying which safety feature(s) failed to function as desired and allowed the sequence of events to occur. These safety features or barriers are anything that is used to protect a system or person from a hazard including both physical and administrative layers of protection. The concepts of the hazard-barrier-target theory of incident causation are encompassed in this tool. (See Chapter 3.)... 

As the density of information derived from efforts to sequence, map and identify human genes increased, so did the demand for analytical tools capable of exploiting this information. DNA microarrays were developed in response to this demand. Southern(69) was the first to describe parallel, in situ ohgonucleotide synthesis as a means of generating oligonucleotide probe arrays on solid supports for highly parallel hybridization analysis. Southern s method uses standard nucleotide synthetic reactions to synthesize the oligonucleotides. The reactions are carried out in a movable chamber, which provides a physical barrier between the reaction chamber and the intended synthesis area. 

Thus any advantage of molybdenum disulphide in an oil in reducing friction will be limited to the boundary and mixed lubrication regions, where the reduction in friction may be considerable. One theoretical analysis suggested that the influence of the dispersed powder depends only on particle shape, size and concentration , or in other words that the dispersed powder is simply forming a physical barrier between the interacting surfaces. It would follow that the same effect could be produced by other dispersed solids, and this was confirmed by studies with zinc sulphide, zinc pyrophosphate and calcium hydroxide. 

Barrier Analysis is a systematic process that can be used to identify physical, administrative, and procedural barriers or controls that should have protected persons, property, and the environment from unwanted energy and prevented the occurrence. (See Chapter 11.)... 

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