BUCHI SpeedExtractor E-916 - Manual (Page 76)

8 Troubleshooting
76 SpeedExtractor E-916/E-914 Operation Manual, Version D
8.1.3 Handling and resolving blockages
When a position gets clogged, the pressure is not relieved when the outlet valve opens and dis-
charges the extract. As a result, the pressure remains high in this clogged position. This entails two
problems: Firstly, there is a possible chance of cross contamination between the pressurized clogged
position and the adjacent low pressure positions during the heat-up step of the subsequent cycle.
Secondly, the cell lift does not open when the process is finished to avoid splashing of the sample.
There are different reasons why blockages can occur during extraction under high pressure and high
temperature using the SpeedExtractor E-916/E-914: inappropriate sample preparation, extraction
parameters, or instrument configuration. Often a combination of these factors can cause blockages.
• An appropriate sample and cell preparation is important to avoid blockages. The use of glass fiber
filters and/or thimbles is recommended for sticky, fine powdery and polymer samples. See sec-
tion 6.3.
• An optimized method is essential. Control the following parameters: temperature, solvent, num-
bers of cycles and hold time. Too high temperatures can lead e.g. to melting of polymer samples.
A short first cycle can be helpful for samples with high concentration of analyte (e.g. fat in food
samples). For more detailed information about sample preparation and method development,
consider BUCHI's Application Notes, Technical Notes and the SpeedExtractor Application Book-
let. Please contact your local representative or BUCHI for these documents.
• Some samples are prone to precipitate upon passing though the cooling unit during the discharge
step. The shorter cooling unit (P/N 053682) does not cool down the sample that much and hence
reduces the risk of precipitation.
NOTE
The method development of a new unknown sample should be carried out on only one position,
preferably position 1. If it is necessary to replace parts for cleaning, position 1 is the position which
can be reached most easily. If a clogging occurs during the method development step, it is possible
to continue with further extractions using the remaining positions.
At the end of the discharge step pressure sensors at the activated positions will check if the pres-
sure is released before continuing with the next step (another cycle or flush with solvent or gas). If the
pressure has not been released to <1 bar, an error message will be shown and the operator should
then follow the instructions. Following the error messages, it will be necessary to release the pressure
manually.
Relieving pressure manually
Open the drain valve manually using the bit wrench P/N 052783. Opening the drain valve results in a
hot steam of solvent for a quick moment. In order to prevent possible splashing, open the safety shield
and put a towel around the clogged position. Close the drain valve and the shield when finished.