A great deal of sludge can be removed from crude oil by proper settling. A recommended settling system consists of two conebottomed tanks, Figure 11, each holding a little more than four days usable supply of fuel.
Sludge in the bottom third is discarded before refilling. The tanks must be housed in a heated building, and each fitted with heating coils.
Immediately after filling, hot water is circulated through the heating coil until the tank is heated to 100ยฐF (38ยฐC). The heat is then shut off and the fuel allowed to settle undisturbed for four days.
During this time, fuel is being used from a second tank. Temperature inside the settling tank building should be maintained above 70ยฐF (21ยฐC), and the tanks must be vented outside the building.
A two-day supply of diesel fuel should be maintained for emergency use. This supply can also be used to start and stop engine when the crude oil fuel is highly viscous or heavy with paraffins.
