4.2 Scrubber Modes of Operation

Theo Wilson -

Scrubber Modes of Operation

 

The Lonestar Scrubber has three modes of operation, these are:

A) Re-circulation

B) Venting

C) Clean blend gas

  

Re-circulation

In re-circulation mode sample is pulled through the sample inlet and through the sensor head passing through the Scrubber before being blended with fresh sample air. In this mode the air in the Lonestar is being continuously re-circulated through the Scrubber with only a very low flow of outside air being drawn through the sample inlet.  This produces a very clean and dry sample and also extends the life of the Scrubber.  However the flow rate into the sample inlet is very low and not well defined.  To set the instrument to operate in this mode, ensure that the gas re-circulation button on the settings screen is turned on. 

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 Figure 27 - Lonestar re-circulation mode

 

In Re-circulation mode a small amount of sample will come out of the Scrubber Vent. 

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A separate line should be made ready to connect to the Scrubber Vent. This line should be checked for chemical compatibility and it is recommended that it is exhausted to a hydrocarbon trap or to a fume hood.

 

 

Venting mode

In Venting mode, air is drawn through both the inlet of the Scrubber Unit and sample inlet to be blended together into the sensor head before being exhausted via the Lonestar exhaust. To operate in this mode ensure that the gas re-circulation button on the settings screen is turned off.

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Figure 28 -Lonestar Venting mode

   

Clean blend gas mode

Clean blend gas mode is similar to venting mode but with a clean gas supply such as nitrogen boil off or a pre-filtered air supply.  To operate in this mode ensure that the gas re-circulation button on the settings screen is turned off.  The bottle/compressor supply of clean dry air is purged through the Scrubber headspace by the pump to generate a clean dry headspace. Operating in this mode increases the Scrubber lifetime indefinitely.

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Figure 29 - Lonestar clean blend gas mode

 

Note that the Scrubber exhaust should always be open to atmospheric pressure for the Clean blend gas mode to work correctly. During setup it is recommended that the gas supply to the Scrubber is increased until there is a small flow (0-100ml/min) coming out of the Scrubber Vent

 

Choice of Scrubber unit

 

To help in the decision as to what Scrubber unit is best suited for a certain application it is recommended that the Owlstone support team be contacted, where they would be happy to discuss and suggest the most appropriate Scrubber for the stated application

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