Viscosity Regulator or Viscotherm, is a device used to measure viscosity of the fuel oil before sending it to the engine. It is generally fitted at the outlet of the fuel oil heater. The regulator is connected with the heater so that it can measure the viscosity of the oil and regulate the temperature at the same time.

Viscosity regulator is an “L” shaped instrument which consists of a small gear pump that rotates at a constant slow speed of 40 rpm. The pump takes suction from the heater discharge and is generally fitted close to it. A regulated flow of fuel is sent by the pump to a capillary tube. The capillary tube is so designed that the form of flow between the inlet and outlet of the tube generates a pressure difference, which is equal to the viscosity of oil flowing through it. the flow through the capillary is laminar, the difference in pressure between each end of the tube is directly proportional to the viscosity of the oil (the higher the viscosity, the higher the pressure differential).

FO Viscosity Controller: Viscotherm

.viscotherm

Viscosity controller malfunction:

.viscosity controller malfunction