Page 237 - Pipeline Risk Management Manual Ideas, Techniques, and Resources

10/214 Service Interruption Risk
Previous excursions, perhaps from the other sources listed High 0 pts
above, may accumulate and later precipitate major events in Excursions are happening or have happened recently. Recent
this category. pipeline activities allow the possibilities of excursions
Note that pipeline dynamics can also precipitate a service (recent maintenance work, change in service, etc.). Frequent
interruption due to a delivery parameter not being met. changes in pipeline products are occurring. Customer
Pressure surges or sudden changes in product flow may not impacts occur or are only narrowly avoided (near misses) by
create a contamination episode, but may interrupt service as a preventive actions.
control device engages or the customer equipment is exposed to Medium 10 pts
unfavorable conditions. Even though these are not contamina- Excursions have happened in the past in essentially the same
tion-related situations, they can be considered here for conven- system, but not recently; or theoretically, there exists a real
ience. possibility of a relatively simple (high-probability) event
Potential for contamination from changes in pipeline precipitating an excursion; occasional changes in product
dynamics is as follows: transported occur.
Low 15 pts
High 0 pts Rare excursions have happened under extreme conditions.
Excursions are happening or have happened recently. Customer Highly effective and reliable prevention mechanisms exist to
impacts occur or are only narrowly avoided (near misses) by correct these rare occurrences. Customer impacts are almost
preventive actions. nonexistent.
Medium 10 pts None 20 pts
Excursions have happened in the past in essentially the same System configuration virtually disallows contamination possi-
system, but not recently; or theoretically, a real possibility bility. Very stable pipeline uses. A customer impact has never
exists in that a relatively simple (high-probability) event can occurred in the present system configuration. High reliabil-
precipitate an excursion. Preventive mechanisms minimize ity, redundant measures are employed to virtually eliminate
customer impacts. possibility of customer impact. No other possible contami-
Low 15 pts nation events can be envisioned.
Rare excursions have happened under extreme conditions.
Highly effective and reliable prevention mechanisms exist to B. Delivery parameters deviation (DPD)
correct these rare occurrences. Customer impacts are almost
nonexistent. The second possibility that must be included in assessing the
None 20 pts risk of service interruption is the failure to meet acceptable
System configuration virtually disallows contamination possi- delivery parameters. Delivery parameters or conditions nor-
bility. A customer impact has never occurred in the present mally include pressure and flow. Product state conditions (vis-
system configuration. High reliability, redundant measures cosity, density, purity, etc.) are usually covered in the product
are employed to virtually eliminate possibility of customer composition specifications discussed previously. Temperature
impact. No conceivable change in pipeline dynamics can may be included as either a delivery condition or as part of a
precipitate an excursion. product state requirement.
General causes of delivery parameter deviations are
These prevention activities can be factored into the assess-
ment for contamination potential due to pipeline dynamics: Pipeline failures
Pipeline blockages
Proven procedures are used for special tasks. Procedures Equipment failures
should reflect knowledge and experience in performing Operator error.
pipeline pigging, cleaning, dehydration, etc., in manners that
prevent later excursions. Conditions upstream of the section assessed must be
A “management of change” discipline establishes a protocol included in the evaluation.
that requires many experts to review any planned changes in As the assessment begins, a list should be developed, based
pipeline dynamics. Such reviews are designed to detect hid- on customer specifications, that shows critical delivery param-
den problems that might trigger an otherwise unexpected eters. Along with each potential delivery requirement, specific
event. mechanisms that could upset those parameters should be iden-
Close monitoring/control of flow parameters is conducted to tified. This list will serve as a prompter for the evaluator as
avoid abrupt, unexpected shocks to the system. assessments are made. Table 10.2 is an example of such atable.
The threat of sabotage will normally increase the risk of
A4. Other pipeline failure and equipment failure, so evaluators should
include the sabotage module when this threat is significant.
This category includes any other potential Contamination
sources. Examples include improper cleaning of pipeline after BI. Pipeline failures
maintenance or change in service or infiltration of ground
water into a low-pressure distribution system piping. When A pipeline failure will usually precipitate a delivery interrup-
such “other” events can be envisioned, they can be assessed tion. The possibility of this is scored by performing the basic
with a qualitative scale. risk assessment detailed in Chapters 3 through 6. The resulting
Potential for contamination from other sources is as follows: index sum is a measure of the failure potential.