2101510MNA H | NGC820 0 AN D PGC 1000 US ER MA NUA L |
29
IMPORTANT NOTE:
Do not use any type of plastic, Teflon
®
, or Teflon
®
-lined braided steel tubing.
Transport tubing must be chromatographically clean. Tubing should be free of hydrocarbon
contamination and particles. During cutting, fitting, and deburring, the technician should ensure that
no particles are allowed to remain in the tubing.
4.4.3
Maintaining phase
When designing sample transport tubing, phase of sample must be maintained. Gases containing high
concentrations of high boiling components can cause problems when they condense on the inside of
the transport tubing surface. To prevent condensation, the sample transport tubing should be heat-
traced to prevent any hydrocarbons or water from condensing in the sample lines (see
).
Figure 4-7: Heat tracing sample line
4.4.4
Sample probe installation
ABB recommends the use of a sample probe to extract the sample from the process stream. A probe
is essential in supplying a representative sample to the analyzer. Without a probe, analytical accuracy
will be negatively impacted and more maintenance will be required on the analytical system.
4.4.4.1
Location
Locate the pipeline coupling on the gas meter run in close proximity to the analyzer. This
allows the stainless-steel sample line from sample probe to the chromatograph to be as short
as possible.
The coupling should be mounted so that the probe can be installed horizontally or vertically on
the meter run pipe. This means the coupling should be mounted on either the top or the side
of the meter run pipe.
The sample probe should not be mounted at the ends of headers, dead T’s, large volume
accumulators or other spots where gas is likely to be stagnant.
Installation should allow the probe to penetrate the center 1/3 of the main gas meter run. This
allows sufficient heat transfer with the flowing gas sample. The sample probe inlet should be
high enough to avoid sampling of liquids at the bottom of the pipe.
The sample probe must be installed where the probe has access to the fastest flow of gas
within the pipe.
The sample probe should be mounted a minimum of five pipe diameters from any device
which could cause aerosols or significant pressure drops.
4.4.4.2
Other considerations
The sample probe line pressure should be as close to 1 atmosphere as possible to reduce
sample transport lag times due to line pack. Sample pressure at the analyzer should be 15 ±
2 psig (103 ± 14 Kpa).
To maintain this pressure at the analyzer filters, it may be necessary to increase sample probe
pressure to a value greater than 15 psig. Pressure is dependent on sample transport tubing
length between the TCR sample probe and the analyzer.
Be sure to use tubing electrical isolators on sample tubing when connected to pipelines that
are not isolated from cathodic protection.
