LUMP SIZE LIMITATIONS
When sizing a screw conveyor, the lump size
of the material and percentages of the lumps
as a proportion to the total amount of material
conveyed may be a consideration in the final
size selection of a screw conveyor. When
figuring the lump size the largest dimension
should be used.
If the material lumps are friable, that is, easily
crumbled, then they would not pose any
serious limitation to the screw conveyor and
could usually be discounted in calculating the
conveyor size.
Three classes of lump sizes apply as follows:
Class 1. A mixture of lumps and fines in
which not more than 10% are
lumps ranging from maximum size
to one half of the maximum; and
90% are lumps smaller than one
half of the maximum size.
Class 2. A mixture of lumps and fines in
which not more than 25% are
lumps ranging from the
maximum size to one half of
the maximum; and 75% are
lumps smaller than one half of
the maximum size.
Class 3. A mixture of lumps only in
which 95% or more are lumps
ranging from maximum size to
one half of the maximum size;
and 5% or less are lumps less
than one tenth of the
maximum size.
The lump ratio, LR, is indicated to show
the usual screw conveyor sizes and may
be used as a guide in sizing conveyors.
Unusual products and sizes should
be referred to Orthman Conveying
Systems for evaluation.