Page 310 - Pipeline Risk Management Manual Ideas, Techniques, and Resources

Comparing pipelines and station 13/287
as shown in Table 13. 15. From this table, a costibenefit ratio is be for reasons of project prioritization or to assist in design
easily calculated. This ratio is used to help prioritize mainte- decisions such as pipeline loops versus more pump stations.
nance and capital expenditures for the next period. The pipeline relative risk scores represent the relative level
AST Inc. utilizes all of their lower cost (high costmenefit of risk that each point along the pipeline presents to its sur-
ratio) options first. They do this with the confidence that their roundings. The scores are usually insensitive to length. If two
process is automatically compensating for risk reduction bene- pipeline segments, 100 and2600 A, respectively, have the same
fits-that is, because all risk points are of the same magnitude, risk score, then each point along the 100-ft segment presents
it makes sense to first exhaust the low-cost alternatives to the same risk as does each point along the 26004 length. Of
improve risk. Then, the more expensive alternatives can be course, the 2600-ft length presents more overall risk than does
explored if risks are still seen as being unacceptable. This yields the 100-ft length because it has many more risk-producing
the greatest amount ofbenefits because resources are most effi- points. A cumulative risk calculation as described in Chapter 14
ciently utilized. adds the length aspect to a risk score so that a 1 00-ft length of
AST Inc. decides to focus improvement efforts on Tank 655 pipeline with one risk score can be compared against a 2600-ft
first, given the higher risks (higher consequences) seen there. length with a different risk score.
They further decide to budget additional resources toward A direct and intuitive way to make comparisons with station
improved secondary containment only for Tank 655. This par- facilities is to recognize that, just as with the pipeline risk
tially offsets the higher receptor risk in that area. The other scores, each point within the station (or station section, if sev-
tanks, having lower risks, will have their secondary contain- eral portions of a station are scored separately) presents a cer-
ment improvements prioritized among all alternative uses of tain risk to its surroundings. To quantify the total risk
resources. The projected impact on risk is demonstrated in introduced by the station, we can use the station’s length and
Table 13.16. width summed together, just as we use the pipeline segment’s
Note from Table 13.16 that AST Inc. controls both the risk length to get a cumulative risk score for the pipeline. So, a sta-
level and the rate of change in this risk management process. tion that is 50 ft wide by 100 ft long has a risk score that applies
They decide whether to systematically and slowly improve to 150 ft. It has the same cumulative risk as a 150-ft-long
their entire tank population or rather to target identified hot pipeline with the same risk score, or as a pipeline segment that
spots for immediate improvements. (Note that the numbers is 300 ft long with half the risk score, and so forth. With this
used in this example merely provide the reader with a sense of simple approach, all station scores can be compared to pipeline
the methodology; they are not necessarily in correct propor- segments using the cumulative risk relationship. Alternatively,
tion, mathematically correct. or representative of actual data.) the risk evaluator may choose to use a perimeter or 2 times the
width + length as a better basis for comparison with pipeline
ROW lengths. Where available, failure rates in stations and
X. Comparing pipelines and stations pipeline ROW respectively can be used to help establish a size-
equivalency relationship.
Operators often want to compare pipeline segments with sta- This approach is consistent with the use ofrelease volume cal-
tions or parts of stations-facilities within stations. This might culations and implied hazard zones for releases. A station with

Table 13.15 Cost-benefit analysis of risk mitigation
Project Risk improvement (%) Cos? ($) Notes

Communicate HHA (tank level alarm) to central control room 8 4K
HHA to central control room plus automatic tank isolation valves 19 21K
Upgrade tank level gauge to laser model 3 9K Replaces 12-yr-old mechanical model
Increase station visits (with formal “rounds”) by 5 hours per week I 16K Improves several risk variables
Require orientation course for all station visitors 3 7K
Annual refresher training for employees 4 18K
Add impermeable liner to secondary containment 12 430K Improves “consequence” side of equation
Increase secondary containment volume by raising dike level 26 620K Improves “consequence” side of equation
Patch damaged dike areas 18 140K
alu-yr NPV or equivalent calculation.

Table 13.16 AST Inc.’s risk improvement plan
Risk scores
Equipmerit tag Current Next yearplan Five-year target Notes
Tank 655 235 178 140 Projects 43C, 22, 16 next quarter; projects 18,14D in subsequent years
Tank 101 I54 151 130 Project 22 next quarter; project 15 in 2 years
Tank 3 15 146 130 130 Project 18, 22 next quarter; then maintain risk level