The maximum lump size is important. The size of a screw conveyor not only depends on the capacity required, but also on the size and proportion of lumps in the material to be handled. The size of a lump is the maximum dimension it has. A closer definition of the lump size would be the diameter of a ring through which the lump would pass. However, if a lump has one dimension much longer than its transverse cross-section, the long dimension or length would determine the lump size. The character of the lump also is involved. Some materials have hard lumps that won’t break up in transit through a screw conveyor. In that case provision must be made to handle these lumps. Other materials may have lumps that are fairly hard, but degradable in transit through the screw conveyor, thus really reducing the lump size to be handled. Still other materials have lumps that are easily broken in a screw conveyor and lumps of these materials impose no limitations.