Category Archives: Validation & Calibration

Distek Center-Chek™

Distek Center-Chek

Raise the dissolution drive head or individual shaft out of the vessel and attach the Distek Center-Chek™ to the stirring shaft per the below requirement.

 USP Toolkit:

When the shaft is properly inserted in the vessel the attached Center-Chek™ should be positioned no more than 2cm below the vessel flange.

 FDA/ASTM Mechanical Calibration:

When the shaft is properly inserted in the vessel the attached Center-Cheks should be positioned so that the bottom centering tool is positioned 2mm above the top of the paddle blade or basket.  The 2nd centering tool should be positioned 80mm above the paddle blade or 60mm above the top of the basket.  

To install the Center-Chek™ onto the stirring shaft squeeze the legs gently together and attach to the shaft. Push inwards on the plastic tip of the Center-Chek™ while lowering the shaft into the vessel.

 Caution: If the tip of Center-Chek™ is not pushed in as it is lowered into the vessel, it may snap off damaging the tool.

When the shaft axis and vessel axis are aligned correctly, as in Fig. A, the Center-Chek™ pointer should not exceed a total sweep of 4mm as it rotates 360° within the vessel.

 Figure B corresponds to the maximum offset tolerance of 2mm from the center axis as described in USP 23.  The Center-Chek™ pointer is allowed to sweep 2mm left and 2mm right during a 360° rotation, for a total deflection of 4mm.

 The proper calculation for centering is the total measured sweep divided by 2.

Tip: If a vessel is slightly out of round, it may be possible to correct an offset condition by rotating the vessel in its mounting hole. An index mark should be made on the underside of the vessel flange and vessel plate.  This allows easy restoration of correct alignment after the vessel is removed and replaced. The vessel should also be marked for identification, and be returned to the same vessel position on the same dissolution system. The Distek Premiere vessel includes an index mark and serial number for this purpose.

Fig. A: Shaft Centered in Vessel

Fig. B: Shaft Offset by 2mm

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