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FIGURE 2 PATENTED VE TECHNOLOGY AERODYNAMIC PROBE FIGURE 3 A SELECTION OF SILCONERT 2000 COATED SAMPLE SYSTEM COMPONENTS (SILCOTEK, 2019)
TIP AND HELICAL STRAKES MINIMISE DETRIMENTAL FLOW
DISTURBANCES

failure due to static bending loads and
vortex shedding behaviour and do not
provide sufficient information on gas
behaviour around the probe tip (inlet),
and the effect that has on measurement
performance. These codes also neglect
and often magnify the problems caused
by the effect of media flow disturbances
on mechanical integrity. This may also
cause inaccuracies on other items of
downstream measurement equipment,
such as flow meters. FIGURE 4 ILLUSTRATION OF THE PIPELINE SIMULATOR AND APPARATUS USED FOR SAMPLING SYSTEM COMPARISON TESTING

The implementation of a finely
polished surface finish and inert
coated tubing is often used throughout
the gas industry.
H₂S is known for its reactive, chemical
adsorptive nature onto steel surfaces.
Therefore, the ability to reliably
transport this molecule to the analyser,
in a timely manner, is crucial to the
measurement. The effects of this
include slow response time with
increased and unnecessary lag time
and an unrepresentative sample
reaching the analyser and yielding an
inaccurate measurement.
The use of inert coated tubing allows
a non-reactive silicon-based coating
to improve sample flow paths for
better process consistency, control
and analytical results. It is essential to
properly employ suitable transport lines
to eliminate issues such as sample loss
and lag/delay from chemical reactions
and adsorption on the surfaces. The results – H2S cycling cycle between a zero gas and span gas,
At Orbital, a H₂S comparative specifically to be able to flow gases of
So, why only use inert coated tubing/pipe? investigation was carried out between interest past the sampling probe tips –
It is possible to utilise sample probes a conditioned conventional system as would be experienced in a pipeline.
that can be coated over all surfaces. and a conditioned VE Technology Also, to ensure a true comparison
This, in theory, could eliminate the system. Neither system utilised inert was made, each set of sampling
effect of H₂S adsorption within the coating in the initial testing, as it equipment was set up to replicate real
sample probe (before entering the inert was not possible to coat all wetted life situations, with typical lengths
coated tubing and other components of parts of the conventional system of sample transport lines, sample
the sample system) and provide a much and the experiment was aimed at conditioning equipment and filters.
more stable and reliable representative ascertaining if the sample system Further to this, it was necessary to
sample. All wetted parts of a sample design features made a difference to ensure sealed conditions at typical
system, from probe tip to analyser inlet, measurement performance, not the pressures found in gas pipelines. The
should be inert coated to minimise application (or absence of) a coating. following actions were taken minimise
adsorption of H₂S and other such The test was performed by using a delays from potential purging, diffusion
sorptive compounds of interest. pipeline simulator on a 15-minute and sorption effects:

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