MORT chart

A barrier analysis for the Tabasco s flooding has been conducted and Table 3 shows the Barrier analysis for the present case. The results of the MORT analysis are presented by colouring-code the chart as follows a red, where a problem is found b green, where a relevant issue is judged to have been satisfactory, and c blue, to indicate where there is a need to find more information to properly assess it. Figures 5-8 show several branches of the MORT chart for the Tabasco s flooding disaster. 

Figure 3-3 The top tiers of the MORT chart. The chart is a fault tree used as both an inspection or appraisal tool and as an accident investigation guide.

The MORT chart contains detailed information to aid in evaluating the hazard analysis process (HAP) and the design effort. In practice, however, the MORT tools and techniques that are most frequently used are in the areas of accident investigation, auditing, appraisal, and p>erformance monitoring. 

The management oversight and risk tree (MORT) chart is a large, complex, negative tree (see Chapter 18). Even though the project evaluation tree (PET) is depicted as a positive tree, it is mentally converted and used as a fault tree for accident analysis applications (see Chapter 16). 

The project evaluation tree is an analytical tree to be used primarily as a graphic check in basically the same manner as the management oversight and risk tree (see Chapter 18). The PET chart, however, contains fewer than 200 event symbols and no transfers the MORT chart contains approximately 1,500 events symbols, multiple transfers, transfers within transfers, and drafting breaks. The PET chart is divided into three branches procedures, personnel, and plant and hardware. 

In side-by-side comparisons with the MORT chart and the mini-MORT chart (see Chapter 18), PET has consistently been more favorably received than either of the others by persons with and without prior MORT experience or training. 

Color coding of the PET chart is recommended, using red for evaluation criteria determined to be less than adequate (LTA), green for items that are adequate, black for criteria or branches of the PET chart than do not apply to the particular project or item being evaluated, and blue to indicate areas with insufficient input data to make a decision. (This color-coding system is the same that is used for the MORT chart and the mini-MORT chart (see Chapter 18). 

Change analysis is one of the techniques associated with the Department of Energy s management oversight and risk tree (MORT) approach to system safety. Unlike the MORT chart itself or some of the other tools and techniques associated with the MORT program, change analysis is a very simple, straightforward process that is relatively quick and easy to learn and to apply. 

The symbols used on the MORT chart are basically those used for other analytical trees (Chapter 10) and fault tree analysis (Chapter 15). They include the rectangle as the general event symbol, the circle as the base event symbol, the diamond as an undeveloped terminal event, the and gate, the or gate, and the ellipse as a constraint symbol (Rgs. 18-1 and 18-2). 

In addition, Bill Johnson used a scroll as a normally expected event and an oval as a satisfactory event. The normally expected event distinguishes events that are typically a part of any system, such as change and normal variability. The satisfactory event describes events that may be accident causal factors but are a necessary part of the operation, like functional (part of the system) people or objects in the energy channel. Also, in addition to using the traditional transfer symbol (a triangle), the MORT chart includes capital letters as drafting breaks and small ellipses as risk transfers (Fig. 18-3). 

Risk transfers are found in two places. They are found next to undeveloped terminal events, and they are found near the top of the chart as assumed risks. The implied logic is that barriers, controls, or evasive actions are not possible or practical in those areas where there are undeveloped terminal events. If activity is continued under these circumstances, then some risk is assumed or accepted. The small assumed risk transfers are used to denote a transfer up to the small ovals under the assumed risk portion of the MORT chart. 

Abbreviations used on the MORT chart include LTA, the most frequently used, which stands for less than adequate DN for did not FT for failed to HAP for hazard analysis process JSA for job safety analysis and finally CS R for code standards and regulations . 

Figure 18-1 Event Symbols. The General Event symbol, Basic Event symbol, and Undeveloped Terminal event symbol are the same as commonly used for other fault trees. The use of the stretched circle for a Satisfactory Event and the scroll for a Normally Expected Event are unique to the MORT chart.

Figure 18-3 Transfers In addition to the triangle commonly used as the transfer symbol for analytical trees, the MORT chart also uses large capital letters as drafting break transfers and small ellipses as transfer symbols for assumed risks.

The event symbols, gates, transfers, and abbreviations are all shown on the legend in the lower left corner of the large MORT chart. 

The analogy and logic are sound, and MORT analysis with the large MORT chart is recommended for those individuals who routinely conduct investigations of major accidents and spend a significant portion of their time serving on accident investigation boards. 

The mini-MORT chart is basically the full-size MORT chart with the bottom tier removed to reduce the number of events to be evaluated from... 

The purposes of the mini-MORT chart are to aid in teaching MORT concepts and, for relatively minor accidents, to serve as a tool for performing MORT analysis on a reduced scale. 

Input requirements for MORT analysis, like those for any other detailed, comprehensive analysis, are extensive. Detailed information about the hardware and facilities, environment, procedures, and personnel directly involved is required for full evaluation of the specific control factors, and additional information about the management system is required to evaluate the policies, procedures, implementation plans, risk assessment program, and other upstream factors. Normally, a combination of interviews, physical inspections, and reviews of many procedures and project documents is required. The MORT chart and/or mini-MORT chart can serve as a planning and organizational tool for the collection of evidence and other relevant information. 

The MORT analysis effort begins as soon as the accident occurs and the accident board is notified. The MORT analysis is usually performed by the trained investigator on the board (or an advisor to the board). The MORT (or mini-MORT) chart is used as a working tool to aid in gathering information and storing information as it is gathered. 

Figure 18-4 Color coding. These colors are generally used on the MORT or Mini-MORT chart when performing MORT Analysis. They are also used for the PET chart.

The MORT chart is designed to encompass any accident situation, and not all parts of the chart are relevant to all accidents. A particular block or branch of the chart that is not applicable is color coded black (or sometimes simply crossed out). Again, if a block or branch is incorrectly colored black, the chance to make needed corrections is lost. 

Figure 18-5 Top Events. The top tiers of the MORT chart indicate that the losses resulting from the accident being investigated result from oversights and omissions or assumed risks or both.

Figure 18-6 Management system factors. The alphanumeric notations near the lower left of each event symbol were originally used as a cross reference to the MORT User s Manual. Later versions of the MORT chart now use page numbers for cross reference purposes.

During the two decades since Bill Johnson introduced the original MORT chart, several modifications have been made by the Systems Safety Development Center. Prior to 1983, the first-tier events under accident on the specific control factors side of the chart were as depicted in Figure 18-7. 

The energy flow and barrier analysis (ETBA) technique described in Chapter 13 evolved from this part of the MORT chart, and the mini-MORT chart was developed from this configuration. This version of the chart had a block (not shown) under the incident branch that indicated that in cases of multiple energy flows the analysis process should be repeated for each energy flow and barrier failure that led up to the accident (Fig. 18-9). 

Figures 18-5,18-6, and 18-10 through 18-13 represent the major upper tiers of the MORT chart but are less than 1% of the total events to be analyzed. The MORT chart is tedious to use not only because of its size but also because of the use of multiple transfers and transfers within transfers throughout the chart (Rg. 18-14) ...

Thus MORT analysis, using the full-size MORT chart, is recommended primarily for major accidents and for use by a trained investigator who has attended at least forty hours of instruction in MORT (preferably one of the SSDC courses or the USAF advanced occupational safety course). 

Whether using the MORT chart or the mini-MORT chart to perform MORT analysis (or using the PET chart for PET analysis), the general approach is to use the chart as a working paper, begin as early as possible, add information as it is obtained until the chart is complete, and then use the com-... 

The following instructions are for performing MORT analysis using the mini-MORT chart. The mini-MORT chart was chosen because it is easier to use and to learn and is probably better suited to all except catastrophic accidents. 

The full-size MORT chart and a manual for it (SSDC-4, Revision 2, MORT User s Manual) are available from the Department of Energy s System Safety... 

The MORT chart and user s manual are also reproduced in MORT Safety Assurance Systems, by William G. Johnson (published by Marcel Dekker, Inc., New York, 1980, in cooperation with the National Safety Council available from the NSC, 444 North Michigan Avenue, Chicago, Illinois, 60611). Working with the 22-inch by 34-inch chart is much easier than working from the dissections of the chart found in MORT Safety Assurance Systems. 

System Safety 2000 is the only known source of instructions for using the mini-MORT chart. 

Figure 18-14 Multiple Transfers. Many branches of the MORT chart need to be evaluated several times.

The event and causal factors chart is developed and expanded as new evidence and information become available. It should also be developed in conjunction with other analyses (change analysis and PET or MORT analysis), and information should be cross-checked (Fig. 19-2). Conditions that are causal factors on the event and causal factors chart should be identified as less than adequate areas on the PET, MORT, or mini-MORT chart. 

Figure 19-2 Relationships between PET or MORT and events and conditions. The event and causal factors chart and the PET, MORT, and/or mini-MORT chart are initiated as soon as the investigation begins and are developed together as evidence is collected.

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