Shaftless

Multiple screws, variable geometry, inclination from horizontal to vertical, jacketed casings, shaftless and ribbon screws, plug seals , and a host of design variants offer scope for innovative and speciahzed functions. 

Conventional feeder screws have full-face flights welded to a centre shaft or tube. Uniform pitch screws are sometimes used in simple feeding applications. In order to secure differential intake of product along the axis of a screw, a range of techniques can be adopted, either individually or in combination where appropriate. Typical constructional features are (see Fig. 4.5) stepped pitch variable pitch stepped or taper centre tube or shaft variable screw diameter part ribbon or shaftless construction. (Occasionally the construction is stepped on the outside diameter.)... 

For feeding applications, shaftless screws are generally short and cantilevered from a drive shaft, which in turn may incorporate a short section of ordinary screw. Very small diameter screws, 10-30 mm in... 

Fig. 5.19 Multiple, cantilever feed screws, with shaftless sections...

One example of a shaftless system for underground gasification of coal is the percolation or filtration method (Figure 21.30) in which two boreholes are drilled from the surface through the coal seam. The distance between boreholes depends on the seam permeability. 

FIGURE 21.30 Shaftless method (percolation method) of underground coal gasification (a) section through boreholes and (h) plan of boreholes. (From Braunstein, H.M. et al., Environmental health and control aspects of coal conversion An information overview. Report ORNL-EIS-94, Oak Ridge National Laboratory, Oak Ridge, TN, 1977.)... 

PRACTICAL INFORMATION FOR RIBBON OR SHAFTLESS SCREW MIXERS... 

Property Plow Type of Mixer Paddle Ribbon Shaftless Screw... 

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