Recently I´ve been doing an intership in a liquefaction gas plant in Peru, in the technical services area, control and instrumentation department. I saw a very interesting things in special in security of the proccess, you know, if the gas escapes pipeline all can end in a big boom! a lot of money is lost and maybe happen an explosion. I will explain in a few lines some of the control devices and controllers.
First of all you have to know the diference between a DCS system and a SCADA system, I will do a post for more information about that. In this plant they use a DCS system for monitoring and control all the variables and packages of the plant. The DCS system is DELTA V from EMERSON
In this DCS you can create the control logic and the HMI view for all the variables, variables with a phisical connection (HART, Foundation Fieldbus, MODBUS, etc)
Example of a control logic
Example of HMI view
The delta V has its own controller pack with its power supply and I/O modules, this controller can be reduntant or not, in the plant all controllers is redundant, for more security.
Also this System has an especial module for safety called logic solver. This module runs only the logics for cause and effect charts, and only has hard wired connection doesn't have bus connection for more security.
This is the diagram of connection for the SIS system and the control system.
The control and Instrumentation is a very interesting topic and I will do more post about this.
See you later
