Height of Basket or Paddle Above Bottom of Vessel
USP: 25mm ± 2mm
ASTM: 25mm ± 2mm
Height setting for baskets and paddles is necessary prior to each test. Although it is part of the qualification process every six months, it should not be assumed that the height does not change between those times, and a check before each test ensures that the tester has been correctly set-up by the operator.
There are a number of useful tools that can be used to verify height.
25mm Ball Spacer
Digital Depth Gauge
Depth setting gauges are designed to set the exact height of the paddle or basket assembly to 25mm simply by placing a 25mm ball or spacer below the paddle or basket, lowering them onto the spacer and fixing into position. A digital depth gauge will provide an absolute accurate reading of the actual height for recording in a log-book.
Once fixed at 25mm, routine verification of the correct height is a very quick and simple process using a 'Go-No Go' Gauge.
With a specification of 25mm +/- 2mm that means that a 23mm spacer should easily fit under the paddle or basket, and a 27mm spacer should not fit at all. A Go-No Go' Gauge has both a 23mm and 27mm spacer and is an indispensable tool.
To eliminate potential errors between vessels (hand-blown vessels will always have some small variations in height), i is important to maintain the same vesels in the same positions all the time. The exception to this are the ASTM-UN vessels which are vacuum formed and identical every time.