Emerson Rosemount 700XA, Reference Manual

Page: 11 / 294

system (SCS) where it is filtered or otherwise conditioned. After conditioning, the sample
flows to the analyzer assembly for separation and detection of the gas components.
Figure 1-1: Gas chromatography process model
A. Process line
B. Probe
C. Sample system
D. Chromatograph oven
E. Gas chromatograph (GC) controller
F. Sample return
G. Slip stream
H. Carrier gas
I. Reference vent
J. Detector vent
K. Analysis results
Separation and analysis
The GC separates the sample gas into its components as follows:
1. A precise volume of sample gas is injected into one of the analytical columns. The
column contains a stationary phase (packing) that is either an active solid or an inert
solid support that is coated with a liquid phase (absorption partitioning).
2. A mobile phase (carrier gas) moves the sample gas through the column.
3. The selective retardation of the components takes place in the column, causing
each component to move through the column at a different rate. This separates the
sample into its constituent gases and vapors.
4. A detector located at the outlet of the analytical column senses the elution of
components from the column and produces electrical outputs proportional to the
concentration of each component.
Output from the electronic assembly is normally displayed on a remotely located personal
computer (PC) or in a distributed control system (flow computer).
Reference Manual Overview
2-3-9000-744 June 2022
Rosemount 700XA 11