Design Of Flow Corrective Insert
How to design the flow corrective insert when the hopper half angle larger than 60?
How to design the flow corrective insert when the hopper half angle larger than 60? when the hopper half angle is less than 60, it can be calulated accroding the method described by Johanson[1].
[1] The Placement of Inserts to Correct Flow in Bins. 1967.
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Inserts For Low Wall Inclinations
If the hopper half angle is greater than 60 degrees it will not be practical to secure wall slip with the form of insert described by Johanson as the inclination to the horizontal will be little more than a self clearing angle, if that, for a cone. However, inserts may be useful in hoppers with shallow converging walls to spread the flow channel and the conversion from a radial flow pattern to a pseudo plane-flow regime will resist arching and prevent ratholing. A review of the many types, functions and objective of hopper inserts is given in Chemical Engineering www.che.com July 2010. P 32 – 37. This is an extensive and valuable subject, both for original equipment and as retrofits, but should be applied with great care by non-specialists. ■
Design of Flow Corrective Insert
How to design the flow corrective insert when the hopper half angle larger than 60?
Employing the method proposed by Johanson [1], the geometric shapes and
locations of triangle insert used were obtained.
The design procedures used to select a correct insert for causing mass flow in the
vertical portion of a bin are as follows: (i) select the insert half-angle 2; (ii) for
given values of internal friction angle , wall friction angle and half hopper angle
1, look up critical values of W/R and c.r. in Figs 7 and 8 of Johanson [1];
(iii) draw a straight line AB with an inclined angle π/2c.r. 2from the horizontal
(see Fig. 5); (iv) draw a straight line CD inclined at angle from the vertical where
tan = tan 1/(1 + W/R); (v) draw a straight line BE inclined at angle 2 (i.e.
insert half-angle) from the vertical. The point E, the intersection of CD and BE,
locates the bottom of the insert, and the size and placement of the insert are then
determined.
[1] J. R. Johanson, The placement of inserts to correct flow in bins, Powder Technol. 1, 328–333
(1967/68).
It is clear to design a proper insert when the hopper half angle is less than 60. But how to design the flow corrective insert when the hopper half angle larger than 60? ■