Neptune Chemical Pump Co., a leading manufacturer of chemical metering pumps, designed its Neptune 500-D Series (Duplex) Diaphragm Metering Pumps for frother applications found in prep plants. The Neptune 500-D Series pumps diesel fuel from one pump head to coat the coal and feeds frother (alcohol) from the other pump head, which makes the coal float on top of the slurry so it can be extracted. The 500-D’s Eze-Clean valve cartridges can be removed from the pump heads without having to disturb the pump’s piping. Neptune’s Variable Oil By-pass stroke adjustment provides better valve performance than variable-linkage designs.