Page 197 - Pipeline Risk Management Manual Ideas, Techniques, and Resources

7/174 Leak Impact Factor
used to estimate hazard zones. Such estimates are an important pipe that would contribute to a specific
part of modeling when absolute risk estimates are sought (see leak location, scaled from 0 to IO.
Chapter 14). The calculations underlying the estimates are Pipe-diameter pipe diameter
important in a relative risk assessment because they identify the Max flow rate pumped flowrate of product
critical variables that make one release potentially more conse- HVA high value area, as defined in this chapter,
quential than another. They also help the evaluator to better susceptible to spill damage
understand the threat from the pipeline and more appropriately Public lands binary measure of presence of national
characterize receptors that are potentially damaged. parks, wildlife refuges, etc. susceptible to
Damage states that can be used to define hazard zones are spill damage
discussed in Chapter 14. Water binary measure of presence of water body
susceptible to spill damage
Population 0-10 point scale indicating relative
IX. Leak impact factor sample population density susceptible to spill
damage
Many approaches are possible for evaluating the relative conse- Water intake binary measure of presence of drinking
quences of a pipeline failure. For each component of the LIF water intake structure susceptible to spill
that should be considered, some sample scoring protocols have damage
been presented. Some additional algorithm samples can be LIF Leak impact factor, as defined in this chapter
found in Appendix E and the case studies of Chapter 14.
This sample algorithm is a high-level screening tool used to
Leak Impact Factor Samples identify changes in consequence along the route of a specific
pipeline. The relative consequences are measured by the LIF,
In this sample LIF algorithm, a liquid pipeline operator uses the whose main components are
relationships shown in Table 7.23 to evaluate the LIE A brief
description of the variables used is as follows: Product hazard (PH)
Receptors (R)
prod-haz product hazard, scored as described in this Spill volume (S)
chapter Spread range or dispersion (D)
spill a score ranging from 0 to 1 .O proportional to
relative volume of potential release; 1 .O where
reflects largest volume spill possible in S is a function of pumping rate, leak detection capabilities,
this risk model drain volume, and emergency response capabilities; and
v1 volume lost to leak prior to system shut
down LIF= PH x Rx S x D
v2 volume lost to leak from detection to system
isolation This model is applied to a pipeline transporting butadiene,
v3 volume lost to leak due to drainage of whose product hazard is greater than for most hydrocarbons-
isolated pipeline section about twice as high as for butane or propane. A higher health
Spread measure of relative dispersion range hazard score (Nh per NFPA), reactivity score (N, per NFPA),
Overland measure of relative dispersion due to and a lower CERCLA reportable quantity create the higher
surface flows hazard level.
Subsurface measure of relative dispersion due to In the initial application of this algorithm, changes in conse-
subsurface flows quence are thought to be driven solely by changes in operating
Drain surrogate for drain volume, this is actually pressure and population density along this pipeline. Other
the upstream and downstream lengths of variables are included in the model but are not used initially.

Table 7.23 Algorithms for scoring the leak impact factor
LIF [(prod-ha) x (spill) x (spread) x (receptors)]
Product hazard (prod-haz) Product hazard is calculated elsewhere and stored as a database variable
Spill { [(Vl) + (V2) + (v3)]/23000)/10 + 0.2 3 components of total spill volume are adjusted by scaling factors
Spread [(overland)/3 + (subsurface)/8J Variables adjusted by scaling factors
Receptors [(population) + (HVA) + (public-lands) Total receptor score is sum of individual receptor scores, weighted elsewhere
+ (wetlands) + (water-intake) + (waters)]
v1 [(ma flow rate)/l2] Spill volume contributed by pumping flow rate
v2 (0) Volume contributed by leak detection and response time; to be included later
v3 [(drain) x (pipe_diameter)*] Contributing lengths of upstream and downstream pipe are adjusted hy pipe
diameter as surrogate volume calculation
High value (HVA)