Page 300 - Pipeline Risk Management Manual Ideas, Techniques, and Resources

Modeling ideas I1 131277
Table 13.10 Maximum probable property damage reduction factors shown below. This shows factors, called risk drivers, that
were determined to be critical risk indicators. The relative
Property. damage reduction factors Credit multiplier weightings of the probability and consequence categories are
also shown.
Process Control Factors
Emergency power 0.98 [0.27Pc,+0.22Pdd+0.19Pp,,+0.15Pnc+0.17P,,] x[0.4CIp+0C,,, +
Cooling 0.97 0.6C,uJ = total station risk
Explosion control 0.84 where:
Emergency shutdown 0.96 P,, = Probability of an equipment-related event
Computer control 0.94
Inert gas 0.91 P,, = Probability of a design deficiency-related event
Operating instructions/procedures 0.91 PPlc = Probability of a pipeline contamination-related event
Reactive chemical review (can substitute P,, = Probability of an event related to natural causes
“risk management program”) 0.9 1 P,, = Probability of damage by a third party
TOTAL impact ofprocess control factors 54% C,p = Consequence to life or property
Material Isolation C,, = Consequence to the environment
Remote control valves 0.96 Cbus = Consequence to business.
Dumpiblowdown 0.96
Drainage 0.9 I This algorithm contains weightings for both probability and
Interlock 0.98 consequence factors. For instance, the designer shows that
TOTAL impact ofmaterial isolation factors 829.6
“natural causes” constitutes 15% of the total probability of fail-
Fire Protection ure and 60% of potential consequences are business related.
Leak detection 0.94 Environmental consequences are assigned a 0 weighting. The
Structural steel 0.95 failure probability categories are comprised of factors as fol-
Buried and double-walled tanks 0.84 lows:
Water supply 0.94
Special systems 0.9 1
Sprinkler systems 0.74 Equipment issues A failure due to the malfunction of a piece
Water curtains 0.97 of station equipment.
Foam 0.92
Hand extinguishers 0.95 Risk Drivers
Cable protection 0.94 Obsolete equipment
TOTAL impact of fire protection factors 38% Antiquated equipment
Equipment complexity.
Design deficiencies A failure due to a deficiency in design.
Using the maximum credit for every item would reduce the loss The deficiency is either a result of improper design or changes
to 17% of an uncredited amount (an 83% reduction in potential in the operation of the station after construction.
damages). Of course, to achieve the maximum credit, many
expensive systems would need to be installed, including foam Risk Driven
systems, water curtains, leak detection, dumpiblowdowns, and Improper capacity
double-walled tanks. Velocity > 100 fps
The loss control credits, as originally intended, do not Adequacy of filtration
account for secondary containment. The loss control variables Control loops.
shown here are generally applied to spill volumes that have Equipment separation
escaped both primary and secondary containment. They can Vaults and lids
also be applied when they minimize the product hazard during Valves
secondary containment (before cleanup). Venting
Table 13. IO is for illustration of the approach only. The eval- Manufacturer flaws.
uator would need to define the parameters under which credit
could be awarded for each of these. The percentage loss reduc- Pipeline contaminants A failure caused by contaminants in
tion may not be appropriate in all cases. the gas stream.
Within station limits, the drainage of spills away from other
equipment is important. A slope of at least 2% (1% on hard sur- Risk Drivers
faces) to a safe impoundment area of sufficient volume is seen Pipeline liquids
as adequate. Details regarding other factors can he found in Construction debris
Ref. [26]. Rust scale and sand
Valve grease
Bacteria (internal corrosion)
VI. Modeling ideas II
Employee safely An injury or accident involving an
Another possible scoring algorithm that has been recom- employee. Note that this factor is not used in the preceding
mended by an operator of natural gas station facilities is algorithm.