Oil and gas production handbook - Process Control and ...

• Field instrumentation: sensors and switches that sense process conditions
such as temperature, pressure or flow. These are connected over single and
multiple pair electrical cables (hardwired) or communication bus systems
called fieldbus.
• Control devices, such as Actuators for valves, electrical switchgear and
drives or indicators are also hardwired or connected over fieldbus.
• Controllers execute the control algorithms so that desired actions are taken.
The controllers will also generate events and alarms based on changes of
state and alarm conditions and prepare data for operators and information
systems.
• A number of servers perform the data processing required for data
presentation, historical archiving, alarm processing and engineering
changes.
• Clients such as operator stations and engineering stations are provided for
human interfaces.
• The communication can be laid out in many different configurations, often
including connections to remote facilities, remote operations support and
similar.
The main function of the control system is to make sure the production, processing
and utility systems operate efficiently within design constraints and alarm limits.
The control is typically specified in programs s a combination of logic and control
function blocks such as AND, ADD, PID. For a particular system, a library of
standard solutions such as Level Control Loop, Motor Control is defined. This means
that the system can be specified with combinations of typical loops, consisting of one
or more input devices, function blocks and output devices, rather than formal
programming.
60