2.3.5 Sample system requirements
Line length If possible, avoid long sample lines. In long s, flow sample lines,
velocity can be increased by decreasing downstream pressure and
using by-pass flow via a fast loop.
CAUTION
Stream switching requires a sample pressure of 20 psig (137.9 kPa).
Sample line tubing material • Use sulfur-inert tubing for H
2
S streams; for all other applications,
use stainless steel tubing.
• Ensure tubing is clean and free of grease.
Dryers and filters Use small sizes to minimize time lag and prevent back diffusion.
• Install a minimum of one filter to remove solid particles. Most
applications require fine-element filters upstream of the gas
chromatograph (GC). The GC includes a 2-micron filter.
• Use ceramic or porous metallic type filters. Do not use cork or felt
filters.
NOTICE
Install the probe/regulator first, immediately followed by the
coalescing filter and then the membrane filter. See Appendix for a
recommended natural gas installation.
Pressure regulators and
flow controllers
• Use stainless steel wetted materials.
• Parts should be rated for sample pressure and temperature.
Pipe threads and dressings Use PTFE tape. Do not use pipe thread compounds or pipe dope.
Valving • Install a block valve downstream of sample takeoff point for
maintenance and shutdown.
• The block valve should be a needle valve or cock valve type, of
proper material and packing, and rated for process line pressure.
Quick Start Guide Installation and start-up
00825-0100-3770 July 2020
Rosemount 700XA 21
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