8.3 Make-up flow

Theo Wilson -

The second heated and deactivated sample transfer line has two ports in it, each with an 1/8” Swagelok connector. They may be blanked off or used to split and make up the sample flow as described below.

Figure_20.png

Make-up flow path (blue) superimposed on rear of the At-Line Sampling Module

  • The make-up flow is a flow of clean, dry air that has not passed through the headspace of the sample. It is used to supplement the sample flow in the following circumstances:
    • When a split flow is being used;
    • Instead of a split flow, to dilute the sample flow and prevent saturation of the detector;
    • If a flow restriction aperture is in place in the particulate filter block, restricting the rate of the sample flow.
  • In all of these cases, the make-up flow is used to bring the total flow through the Lonestar detector to a value that will ensure good operation (1.5-3.0 l/min).
  • The make-up flow comes from the Clean Air port on the Lonestar and is split off from the sample flow by means of a Swagelok tee.
  • The make-up flow should be connected to the second port in the sample transfer line, after the sample flow has passed through the particulate filter.
  • As with the split flow, the make-up flow rate may be controlled by a rotameter or mass flow controller. Alternatively, a flow-restriction aperture may be used (see Apertures section below).
  • While running the Lonestar with a make-up flow, the sample flow may also be controlled by a rotameter or mass flow controller inline (before the inlet to the sample bottle). Alternatively, a flow restriction aperture may be installed in the particulate filter block (see Apertures section below).
  • Please note that if an aperture is installed in the particulate filter block, the sample flow rate by itself may not be large enough to ensure good operation of the Lonestar detector (1.5-3.0 l/min). To switch back to running the Lonestar without a make-up flow, it will be necessary to remove the aperture from the block.
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