Page 292 - Pipeline Risk Management Manual Ideas, Techniques, and Resources

Risk assessment model 131269
’4. Design B. Construction
Overpressurepotential A measure of the susceptibility of the Because of the age of many station facilities and the construc-
facility to overstressing is a valid risk variable. The safest con- tion philosophies of the past, complete construction and test
dition is when no pressure source exists that can generate suffi- records of the facilities are typically not available. Evidence to
cient pressure to exceed allowable stresses. Where pressure score construction-related items might have to be accumulated
sources can overstress systems and safety systems are needed from information such as leawfailure histories, visual inspec-
to protect the facility, then risk increases. This includes consid- tions of the systems, and comparisons with similar systems in
eration of the pumping head, which can overfill a tank. It also other areas. Score these items for inspection, materials, joining,
includes consideration of changing allowable stresses due to backfill, handling, and coatings as described on pages
changes in temperature. Note that the adequacy of safety sys- 124- 125.
tems and the potential for specialized stresses such as surges
and fatigue are examined elsewhere in this model. It is common C. Operations
in the industry for systems to contain pressure sources that can
far exceed allowable stresses. Station operations typically have more opportunities for errors
Overpressure of customer facilities should also be consid- such as overpressure due to inadvertent valve closures and
ered for station facilities. It is primarily the responsibility of the incorrect product transfer resulting in product to the wrong
customer to protect their facilities downstream from a custody tank or to overfilled tanks. Some changes are made from the
transfer station from an overpressure event. When in-station basic risk assessment model for scoring items in this part ofthe
piping directly supplies adjacent customer stations, or when it incorrect operations index, as discussed next.
laterals off a mainline pipe end at a custody transfer station
(e.g., block valve, manifold, regulators, meter set), the cus- CI. Procedures Score as described on pages 125-126, with
tomer’s downstream overpressure protection scheme should he the following additional considerations.
examined to confirm that their safety system capabilities are A comprehensive and effective “procedures program” effort
designed to prevent overpressure of downstream equipment should capture all current station facility design, construction,
and piping. In general, score these items for design, hazard ID, maintenance, operations, testing, emergency response, and
MAOP potential, safety systems, material selection, and management related procedures. Current station procedures
checks as described on pages 1 19-124. that are considered important or required to adequately operate
the station should be available at each station or easily accessi-
Safety systems Risk is reduced as safety systems are able to ble to station personnel. Key station-related activity procedures
reliably take independent action-without human interven- should allow for the recording of data on procedure forms
tion-to prevent or minimize releases. Although there is no real (records) for personnel review and future use. There should be
standard in the industry, most agree that if false alarms can be no recent history of station procedure-related problems.
minimized, then safety systems that close valves, stop pumps, All procedures should be appropriate for the necessary type
and/or isolate equipment automatically in extreme conditions (design, operations, maintenance, etc.), conditions (location,
are very valuable. Early warning alarms and status alerts when personnel skills, systems complexity, etc.), best practices
actions are taken should ideally be sent to a monitored control (industry, company, etc.), communications method (written,
center. Also valuable is the ability of a manned control center to verbal, video), and needs (job safety analysis, job task analysis,
remotely activate isolation and shutdowns to minimize dam- job needs analysis). Several layers of procedures should be in
ages. Not as valuable, especially for unmanned, infrequently place, ranging from general corporate policies (is., IO princi-
visited sites, are safety systems that merely produce a local ples of conduct) to guideline standard practices (Le., damage
indication of abnormal conditions. prevention program) to station-specific procedures (Le., abnor-
Safety system actions that provide increasing station facility mal operations procedures) to detailed job task recommended
overpressure protection include equipment shutdown, equip- practices (Le., valve manufacture maintenance procedures).
ment isolation, equipment lock-out, station isolation, station Many technical writing ‘best practices’ could be listed to pro-
lock-out, and full capacity relief. Lock-out typically requires a vide guidelines for “what makes an excellent procedure,” but
person to inspect the station conditions prior to resetting trips this is outside the scope of this text.
and restarting systems.
Management of change A formal management of change
Safety systems evaluation To ensure the adequacy of safety (MOC) process should be in place that identifies facility proce-
systems, periodic reviews are valuable. Such reviews should dure-related changes that may affect the procedures program
also be triggered by formal management of change policies or and provides adequacy review guidelines (see below). A formal
anytime a change in made in a facility. HAZOPS or other haz- written process should exist that provides best practices for
ard evaluation techniques are commonly used to first assess the field personnel’s modification of company procedures, includ-
need and/or adequacy of safety systems. This is often followed ing communication of changes, procedure revision, and change
by a review of the design calculations and supporting assump- distribution and implementation. Recent procedure changes
tions used in specifying the type and actions of the device. The should be incorporated into company standards, recommended
most successful program will have responsibilities, frequen- practices, and local procedures for daily use by station person-
cies, and personnel qualifications clearly spelled out. DOT nel. Procedure changes that are more than 3 months old should
requires or implies an annual review frequency for overpres- be reflected in newly issued procedures accompanied by a
sure safety devices. change log.