Siemens GC..M.. Manual de instalación descargar pdf (Pagina 30)

Sampling System Installation, Continued

Liquid Samples

If the sample stream is a liquid, all of the liquid flows should be returned to the process. It is easiest to

return both the sample bypass and analyzer flows together; however, if the differential pressure available

at the analyzer house is less than 10 psig (69 kPa), a separate power pressure return is required for the

analyzer flow (typically 20 cm

/min.) If the liquid could reverse flow in the process line, install check

valves where applicable.

Make sure the return tubing is long enough to reach the connection points. Cap the open ends of the

tubing to prevent contamination.

Vents, Drains, or Means of Returning Samples to the Process Stream

If the sample gas is to be returned to a pressurized line, an atmospheric reference valve (ARV) is

required in the sampling system. The return line should have only a very low pressure (0 to 20 psig [0 to

138 kPa]). Install a check valve to prevent backflow.

When returning a gas sample that can condense, slope it downward to a liquid drain or return it to the

process stream using heat tracing to prevent any condensation. For details on installing heat tracing,

refer to the "Sampling System" description in this section.

If the sampled stream is a liquid, all of the liquid flows should be returned to the process. It is easiest to

return both the sample bypass and analyzer flows together; however, if the differential pressure available

at the analyzer house is less than 10 psig (69 kPa), a separate lower pressure return is required for the

analyzer flow (typically 20 cm

/min.) If the liquid could reverse flow in the process line, install check

valves where applicable.

Make sure the return tubing is long enough to reach the connection points. Cap the open ends of the

tubing to prevent contamination.

WARNING All vent lines and oven exhaust should be vented outside the shelter. The vents

should be connected to a location where the pressure is atmospheric. Connection of oven or

analyzer vents to a variable pressure source such as a flare header should not be done as

chromatographic performance will be severely affected. Backpressure on the oven vent could

cause the T-rating of the instrument to be exceeded, which might become an ignition source.

Refer to the comments on Hazardous gases on page 3.

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Siemens GC..M.. Manual de instalación Pagina 30