[[:file:surface-production-equipment_fig5.png|Figure 5]] shows a typical vertical heater treater. Notice that a heater treater is simply a separator in which a firetube has been placed to heat the liquid mixture as it enters the vessel. This heating of the oil and water mixture reduces the viscosity and promotes the separation of the two phases. The fuel for the firetube is usually taken from the gas produced from the well.
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[[:file:surface-production-equipment_fig5.png|Figure 5]] shows a typical vertical heater treater. Notice that a heater treater is simply a separator in which a firetube has been placed to heat the liquid mixture as it enters the vessel. This heating of the oil and water mixture reduces the [[viscosity]] and promotes the separation of the two phases. The fuel for the firetube is usually taken from the gas produced from the well.