Page 74 - Oil and Gas Production Handbook An Introduction to Oil and Gas Production

• Optimization of various processes to increase capacity or reduce
energy costs.
• Pipeline management modeling, leak detection and pig tracking.
• Support for remote operations, in which facility data is available to
company specialists located at a central support center.
• Support for remote operations where the entire facility is unmanned
or without local operators full or part time, and is operated from a
remote location.

6.1.2 Emergency Shutdown and Process Shutdown
The process control
system should control the
process when it is
operating within normal
constrains such as level,
pressure and temperature.
The Emergency Shutdown
(ESD) and Process
Shutdown (PSD) systems
will take action when the
process goes into a
malfunction or dangerous
state. For this purpose the
system maintains four sets
of limits for a process
value, LowLow (LL), Low
(L), High (H) and HighHigh
(HH). L and H are process
warning limits which alert
to process disturbances. LL and HH are alarm conditions and detect that the
process is operating out of range and there is a chance of undesirable
events and malfunction.

Separate transmitters are provided for safety systems. One example is the
LTLL (Level Transmitter LowLow) or LSLL (Level Switch LowLow) alarm for
the oil level. When this condition is triggered, there is a risk of blow-by which
means gas leaks out of the oil output and gives high pressure in the next
separation stage or other following process equipment such as a desalter.
Transmitters are preferred over switches because of better diagnostic
capabilities

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