SCD 8355 Reaction Cell pressure.

Hi LabGuy,

Thanks for including information about the issue you are experiencing, as well as the troubleshooting you've done up to this point.

Reaction cell pressure should typically be below 7 Torr normally, and between 0-2 Torr with the transfer line capped. The reason it should be at such a low value is because the vacuum is being pulled directly from the reaction cell by the pump. Whenever I see high reaction cell pressure, my first instinct is to check the vacuum pump and hose connections to ensure that everything is still airtight and secure. During an Agilent Preventative Maintenance visit, the reaction cell and vacuum pump are maintained together at the same time.

When we add the Ozone trap onto the pump, we are essentially increasing the work the pump needs to do to pull a vacuum at the reaction cell. I would expect that removing the ozone trap would allow the pump to achieve a lower pressure at the cell due to this restriction being removed.

My first recommendation would be to ensure that the pump oil is clean and at the appropriate level, and to change the oil mist filter if this hasn't been done recently. If you are still seeing the issue after checking the pump, you may have an issue with an internal part of the detector needing to be replaced. There are O-rings within the detector's optical filter and reaction cell that help maintain an airtight seal. Over time these O-rings may get repositioned or lose some of their elastic properties, which can introduce leaks into the cell.

If you continue to see this issue or need any help with the recommended troubleshooting steps above, please reach out to our technical support team by navigating to the following link: Contact Us | Agilent. We would be happy to discuss this issue in further detail!

Solved!!!  The pressure leak ended up not being in the reaction cell at all.  I narrowed it down to the block/weldment that the pressure transducer is in.  There is an O-ring in the fitting that exits to the reaction cell.  To clarify, it was NOT the transducer O-ring.  I didn't see this in any maintenance/service manual.  Now we know.