Page 294 - Pipeline Risk Management Manual Ideas, Techniques, and Resources

Risk assessment model 13/271
the training being conducted and clear task/position qualifica- depending on the consequences of their failure to perform as
tion objectives, testing methods, minimum requirements, and designed. Where reliance is placed on another company’s
refresher requirements should be documented as part of an safety system, risk is increased. The extra risk can be partially
overall company personnel qualification program. reduced to the extent that witnessing of the other company’s
Several layers of training and testing may need to be in place PPM activities takes place.
to cover general corporate policies, standard practices, station-
specific procedures, and detailed job task recommended prac- AntzJLeeze program In many regions, freeze prevention is a
tices. Many personnel training and testing details could be critical part of failure avoidance. This can be added to the risk
listed to provide guidelines for “what makes an excellent quali- assessment when appropriate. For maximum risk-reduction
fications program,” but this is outside the scope of this book. credit, each potential “dead space” that can be exposed to prod-
A formal MOC process should be in place that identifies uct and subzero ambient temperatures should be on a seasonal
personnel qualification-related changes that may affect the or annual “antifreeze” maintenance program that includes
qualifications program and provides adequacy review guide- identifying all potential equipment, component, piping, tubing,
lines (see below). A formal written process should exist that or sump areas where water can collect and freeze causing mate-
provides best practices for field personnel’s modification of rial stresses, cracks, or failures. Examples of practices to
local qualification requirements, including taskiposition prevent freeze problems include the following:
changes, communication of changes, and change distribution
and implementation. Recent program changes should be incor- To protect station sensing tubingipots, an appropriate solu-
porated into company practices, procedures, and documents for tion of fluid is injected every fall where facilities are vulnera-
daily use by station personnel. Program changes more than ble.
3 months old should be reflected in newly issued program To protect station piping, low spots are removed or pigged
documents accompanied by a change log. and dead legs are flushed periodically during cold weather.
Station valve stems and lubrication tubing are injected with
C7. Mechanical error preventers This variable is fully low-temperature grease each fall.
described onpages 131-132. Pump drains and sumps are periodically flushed during cold
As a means of reducing human error potential and enhancing or heat traced aboveground (buried below grade).
operations control, computer permissives are routines estab-
lished in local logic controllers (field computers) or central The risk evaluator should look for a comprehensive and effec-
host computers (see earlier discussion of SCADA systems). tive “antifreeze” effort that is incorporated into the station
These routines help to ensure that unsafe or improper actions, PPM program. Specific facility design, maintenance, and
including improper sequencing of actions, cannot be per- operations procedures should also exist and be maintained to
formed. They are most often employed in complicated, multi- cover all program requirements. A formal MOC process
step procedures such as station starts and stops and pump should be in place that identifies facility conditions or design-
line-ups. Also in this category are control functions that cover related changes that may affect the antifreeze program and
more complex routines to interpret raw data and that take provides adequacy review guidelines (see below). There
actions when preset tolerances are exceeded. Examples ofcom- should be no recent history of equipment/material freeze-
puter permissives include routines that prevent a pump from related problems.
starting when the discharge valve is closed, delay a pump shut-
down until a control valve has reached a certain position, open a Leak impact factor
bypass valve when a surge is detected, and automatically start
or stop additional pumps when flow and pressure conditions are The potential consequences from a station spill or release can
correct. be assessed in the general way described in Chapter 7. This
involves assessment of the following consequence compo-
D. Muintenance nents:
As in the pipe-only assessment, a low score in maintenance Product Hazard
should cause doubts regarding the adequacy of any safety sys- Spill Size
tem that relies on equipment operation. Because features such Dispersion
as overpressure protection and tank overfill protection are criti- Receptors
cal aspects in a station facility, maintenance ofpressure control
devices and safety systems is critical. Score the maintenance Where special considerations for stations are warranted, they
practices for documentation, schedule, and procedures as are discussed here.
described on page 132. In most modem hydrocarbon pipeline stations, a leak of any
Whereas some regulations mandate inspection and calibra- significant size would be cause for immediate action. Gaseous
tion frequencies of certain safety devices, it is common indus- product pipeline stations typically control compressor or pres-
try practice to perform regular PPM activities on all “critical sure relief discharges by venting the gas through a vent stack
instruments.” The term critical instrument should be defined within the station. In the case of high-pressureivolume releases,
and all devices so labeled should be identified and placed on a large-diameter flare stacks (with apiloted ignition flame) com-
special, formal PPM program. Commonly, pressure relief bust vented gases into the atmosphere. Gas facilities are nor-
valves, rupture disks, and certain pressure, temperature, and mally leak checked periodically and remotely monitored for
flow sensors and switches are considered critical devices, equipment or piping leaks.