The pumping of solids usually refers to mixtures of liquid and solid constituents such as sewage, agricultural slurries, hazardous waste and industrial process sludges being transported within an enclosed pipeline. Each type of material has its own physical and chemical characteristics in terms of, solids content, maximum particle size and flow behaviours, although not every one can necessarily be pumped, due to lack of plasticity, for example.
In addition to their more common use in waste treatment plants, pressure and vacuum solids handling pumps are in use in a wide range of applications, for example at BMW's "state of the art" engine manufacturing facility outside Munich, to the more mundane, such as can be seen at almost every construction site, where concrete is delivered using two-cylinder piston pumps with an S-transfer tube.
There are two principal types of pumps used for handling solids, the rotary and the reciprocating, of which the latter has the widest range of applications. Rotary pumps include centrifugal, screw and peristaltic formats. Reciprocating pumps can be subdivided into plunger, diaphragm and piston formats, using either single cylinder or two-cylinder "push-pull" configurations.
In terms of applications, the single-cylinder type pumps, or High Solids Pumps, are suitable for bulk materials with a coarse composition - for example wood chips, organic waste, hazardous waste or shredded paper, whilst the two-cylinder pump is more suitable to materials with a smoother profile - such as cement, mine tailings and sewage sludges.
There is a good selection of quality pump manufacturers to choose from, including such leading brand names as; Grundfos, Lowara, Flygt, KSB, Mono and ABS.
