Paddle shaft

Close inspection of USP Apparatus 1 and 2 before use can help identify sources of error. Obviously, dimensions should be as specified. In cases of both baskets and paddles, shafts must be straight and true. The paddles are sometimes partially coated with Teflon. This coating can peel and partially shed from the paddle, causing flow disturbance of hydrodynamics within the vessel. Paddles can rust and become nicked or dented this can adversely affect dissolution hydrodynamics and be a source of contamination. Thorough cleaning of the paddles is also important, to preclude carry over of drug or medium. 

Figure 10 Rotational (tangential) flow (UA) as a function of stirring rate (co) for paddle (filled circles) and basket (open circles) Mean SD position S2 approximately 1 cm above the paddle and midway between the paddle shaft and the wall of the dissolution vessel. (Please note that, in contrast to simulation techniques such as, for instance, computational fluid dynamics, these data are based on dissolution experiments.) Source Data from Ref. 10, UPE method.

Figure 15 Variation coefficient v as a function of the dimensionless mixing time for different L/D ratios. Copper and nickel particles of

Diameter and length of the drum Diameter of the paddle shaft Mean particle diameter Degree of fill of the drum... 

When dealing with small volumes, a fairly common approach has been to take the glass vessel and reduce its size to 100-200 mL, and to also scale down the size of the paddle shaft or basket shaft and baskets accordingly (Fig. 11.1). In most cases, the modified and smaller vessels are configured within the standard dissolution tester. Table 11.1 provides a comparison between standard USP dissolution Apparatus 2 and minidissolution assembly. Because the minidissolution assembly is not compendial, chemical and mechanical calibration procedures should be developed for performance verification. 

Other variations of the rotary drum mixer-agglomerator, fitted with either lifting blades or independent paddle shafts, are also used in feed preparation for sintering operations (see Section 2, Chapter 4). 

Equipped with counter-rotating paddle shaft Paddle assembly diameter 36 in. 

Since about 1990 the paddle or infeed rolls can also be driven separately, each from a slip-on type geared motor. Frequency control gives infinite variabihty of the paddle shaft speeds, so that these can be optimally adapted to the auger shaft speed (Fig. 38). 

Basket and paddle shafts must be perpendicular to the base plate Distance between shaft axis and vertical axis of the vessel should be <2 mm... 

Change-can mixer (pony mixer) n. A type of planetary mixer comprising several paddle blades mounted on a vertical shaft rotating in one direction while the can or contained counter-rotates. The paddle shaft is usually mounted on a hinged structure so that it can be swung out of the can, permitting the can to b removed, emptied, and replaced easily. This type of mixer is employed for relatively small batches (12-480 L) of fluid dispersions and dry materials. 

Alternatively, paddle shafts can be installed at the head end of a discharge conveyor for sticky materials such as loam or chalk. With this arrangement the material is, as it were, chopped or sliced off as it emerges from the hopper outlet and is then fed in a uniform layer to the conveyor (Fig. 39). 

Fig. 39 Paddle shafts for the discharge of sticky material from a bunker...

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