centrifugal separator · separation system

Alfa Laval ALCAP S-916

The Alfa Laval ALCAP S-916 is a marine centrifugal separator, a machine that cleans fuel oil or lubricating oil aboard ship by spinning it at high speed so that water and solid contaminants, being denser than the oil, are thrown outward and separated from it. Centrifugal separation is vital on ships that burn heavy fuel oil, because that fuel arrives contaminated with water, sludge and catalytic fines that would damage the engine if not removed before the fuel reaches the injection system, and the same principle is used to keep lubricating oil clean in service. What distinguishes the ALCAP concept is its method of controlling separation. Traditional purifiers rely on a gravity disc, a ring of a specific size that must be selected to match the density of the oil being treated and that sets the position of the oil–water interface in the bowl. The ALCAP system dispenses with the gravity disc and instead continuously monitors the quality of the cleaned oil leaving the separator; when the sensor detects that water is beginning to break through into the clean oil, the control system triggers the separator to discharge the accumulated water and sludge. This makes the machine largely self-adjusting across a wide range of oil densities and water contents, which is a real advantage as fuels vary. In operation the separator is a self-cleaning disc-stack machine: the oil passes through a stack of closely spaced conical discs that greatly increase the effective settling area, and the bowl periodically opens to eject the separated sludge and water without stopping the process. Correct feed rate, heating of the oil to the right temperature and viscosity, and proper maintenance of the bowl, discs and seals are all essential to good separation. Machines of this kind, arranged as fuel and lubricating oil treatment units, are a core part of a ship's engine-room auxiliary systems, protecting the main and auxiliary engines from the wear and damage that dirty oil would otherwise cause.