HYDROCARBON
ENGINEERING
36
down to proper compensation for changes in volume caused
by temperature variations.
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DeltaV automated control driving valve actuators can create
lineups in an instant, eliminating the need for operators to
walk through and check potentially dozens of valves and
segments over thousands of metres.
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Instrumentation can detect spills and determine where other
releases are happening in a facility. Spilled product wastes
money in addition to creating HSSE issues.
Terminal management covers all activities at a facility:
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Inventory monitoring includes quality and quantity of
contents, heating or cooling if necessary, blanketing for fire
suppression, and corrosion monitoring to avoid leakage.
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Process control encompasses movements, vapour recovery,
in tank actions, blending, and other processes required by
customers.
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Asset management monitors the operation, utilisation and
condition of equipment including jetties, gantries, piping,
pumps, instrumentation and safety devices.
All of these capabilities have to work together flawlessly to
keep the operation performing at peak capability. A failed pump
motor or a leaking valve can prevent a critical lineup from being
implemented, delaying product movement or causing a spill or
contamination. Valves not closing fully can allow inventory loss
or products to mix, creating contamination issues.
An effective terminal automation system performs two major
functions. First, it has to be the terminal’s cash register and
bookkeeper, recording all flows in and out including custody
transfers and product movements. All the data comes from the
facility’s instrumentation through the process control system.
The second function is process control, monitoring and
operating all the valves, pumps, instruments and safety systems.
These two main functional areas may be supported on totally
separate platforms, but they must be integrated seamlessly
because information and data needs to constantly flow from one
to the other.
Product transfer and load out
In most cases, a terminal is not a consumer of products it
handles, at least not in any significant amounts. It makes money
Figure 2.
All the elements of a terminal operation, including
inventory management, are interrelated and perform
best when controlled by a seamlessly integrated terminal
management system.
by storing and moving product in and out, sending it
on to the final customer or the next processing phase.
Some products may be stored on the site for some
period of time, but in most cases, the less time in
storage, the better.
Many facilities have various pipeline connections
going in and out, along with the ability to load and
unload bulk carriers such as trucks and railcars, and, if
there is access via waterway, tankers and vessels. On
any given day product can be moving from any one of
those to any other causing a variety of challenges:
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Custody transfer data must be accurate at all
times: all the products stored or moving through a
facility represent money, so the ability to know
exactly how much product is moving and its value
is paramount. Without the highest level of
measurement accuracy, recognised and accepted
by all sides, customers can contest the validity of
transactions.
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Effective maintenance to keep pumps and valves
at peak performance: condition-based
maintenance is a critical part of asset management
because it can warn of developing problems while
there is opportunity to solve an issue before it
becomes an operational issue. Without such an
approach, maintenance becomes reactive instead
of proactive, either allowing outages to develop at
the worst times, or adding to costs due to wasted
efforts fixing things when not necessary.
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Accurate and fast lineups permit more throughput
while avoiding inventory loss. Consider this
example: the contents of a vessel must be
unloaded to a tank near a jetty and then
transferred to a truck. If the terminal is large, those
two places could be several thousand metres
apart, and a dozen or more valves may need to be
set correctly to establish the proper lineup. With a
typical manual procedure, an operator needs to
walk through the lineup, checking or changing each
valve so it is in the correct position, and reporting
on each to the control room by radio. If the
operator is conscientious and qualified, this can be
an accurate and reliable procedure, but it could
easily take an hour or two, and if he or she makes
an error in valve identification, the result could be
disastrous. When valves are automated, they can
be controlled and monitored by the automation
system, allowing the correct lineup to be
established and verified in minutes. Lineups can be
stored in libraries, allowing them to be used
whenever needed, and special operations can be
verified to avoid safety incidents.
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Broader ranges of products can be handled
without contamination: terminal operators
frequently cite operational problems caused by
increasing numbers of products. As product types
increase, so do opportunities for contamination.
Keeping product families and grades separate using
manual systems adds a level of complexity
difficult for operators to manage, whereas the task
is much simpler with automation.
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Delays due to equipment failures can be minimised
or even eliminated: if a vessel pulls into the dock
and needs to be unloaded, the owner expects it to
