Page 142 - Pipeline Risk Management Manual Ideas, Techniques, and Resources

Design 6/119
of issues are really not errors since they presumably were deter- information can be reconstructed. In the absence of data, a phi-
mined based on best industry practices at the time. For a risk losophy regarding level gfproofcan be adopted. Perhaps more
assessment, they are normally better assessed in the Design so than in other failure modes, hearsay and employee testimony
Index if they relate to strength (wrinkle bends, low frequency might be available and appropriate to varying degrees. The con-
ERW pipe, etc) or in the Corrosion index if related to periods servative and recommended approach is to assume higher risks
with no cathodic protection, incomplete pipe-to-soil reading when uncertainty is high. As always, consistency in assigning
techniques, etc. points is important.
Actions such as vandalism, sabotage, or accidents caused This portion of the assessment invdves many variables with
by the public are not considered here. These are addressed to low point values. So. most variables will not have a large impact
some extent in the third-party damage index and in the optional on risk individually, but in aggregate, the scores are thought to
sabotage module discussed in Chapter 9. present a picture of the relative potential for human error lead-
Many variables thought to impact human error potential are ing directly to a pipeline failure.
identified here. The risk evaluator should incorporate addi- Because the potential for human error on a pipeline is related
tional knowledge and experience into this index as such knowl- to the operation of stations, Chapter 13 should also be reviewed
edge becomes available. If data, observations, or expert for ideas regarding station risk assessment.
judgment demonstrates correlations between accidents and
variables such as years of experience, or time of day, or level
of education. or diet, or salary. then these variables can be A. Design (weighting: 30%)
included in the risk picture. It is not thought that the state ofthe
art has advanced to that point yet. This is perhaps the most difficult aspect to assess for an existing
Human interaction can be either positive-preventing or pipeline. Design and planning processes are often not well defined
mitigating failures, or negative-exacerbating or initiating or documented and are often hghIy variable. Consequently, they
failures. Where efforts are made to improve human perform- are the most difficult to assess for an existing pipeline.
ance, risk reduction is achieved. Improvements may be achieved The suggested approach is for the evaluator to ask for evi-
through better designs of the pipeline system, development dence that certain error-preventing actions were taken during
of better employees, and/or through improved management the design phase. It would not be inappropriate to insist on doc-
programs. Such improvements are a component ofrisk manage- umentation for each item. If design documents are available, a
ment. check or certification of the design can be done to verify that no
An important concept in assessing human error risk is the obvious errors have been made.
supposition that small errors at any point in a process can Aspects that can be scored in this portion of the assessment
leave the system vulnerable to failure at a later stage. With are as follows:
this in mind, the evaluator must assess the potential for
human error in each of the four phases of a pipeline's life: AI. Hazard identification 4 pts
design, construction, operation, and maintenance. A slight A2. MOP potential 12 pts
design or construction error may not be apparent for years A3. Safety systems 10 pts
until it is suddenly a contributor to a failure. By viewing the A4. Material selection 2 pts
entire pipelining process as a chain of interlinked steps, we A5. Checks 2 pts
can also identify possible intervention points, where checks
or inspections or special equipment can be inserted to avoid a Al. Hazard identification (0-4 pts)
human error-type failure. Because many pipeline accidents
are the result of more than one thing going wrong, there Here, the evaluator checks to see that efforts were made to
are often several opportunities to intervene in the failure identify all credible hazards associated with the pipeline
sequence. and its operation. A hazard must be clearly understood
Specific items and actions that are thought to minimize the before appropriate risk reduction measures can be employed.
potential for errors should be identified and incorporated into This would include all possible failure modes in a pipeline
the risk assessment. A point schedule can be used to weigh the risk assessment. Thoroughness is important as is timeliness:
relative impact of each item on the risk picture. Many of these Does the assessment reflect current conditions? Have all initi-
variables will require subjective evaluations. The evaluator ating events been considered?-even the more rare events
should take steps to ensure consistency by specifying, if such as temperature-induced overpressure? fire around the
only qualitatively, conditions that lead to specific point facilities? safety device failure? (HAZOP studies and other
assignments. The point scores for many of these items will appropriate hazard identification techniques are discussed in
usually be consistent across many pipeline sections if not Chapter 1 .)
entire systems. Ideally, the evaluator should see some documentation that
Ideally, the evaluator will find information relating to the shows that a complete hazard identification was performed. If
pipeline's design, construction, and maintenance on which documentation is not available, she can interview system
risk scores can be based. However, it is not unusual. especially experts or explore other ways to verify that at least the more
in the case of older systems, for such information to be partially obvious scenarios have been addressed.
or wholly unavailable. In such a case, the evaluator can take Points are awarded (maximum of 4 points) based on the
steps to obtain more information about the pipeline's history. thoroughness of the hazard studies. with a documented, current,
Metallurgical analysis of materials, depth-of-cover surveys, and formal hazard identification process getting the highest
and research of manufacturers' records are some ways in which score.