Lubrication pumps are usually positive displacement type of pumps. They are usually gear-type pumps. Most codes require these pumps to be spared, and the spare pumps have a separate source of power since these turbines would be very badly damaged if the lubrication were to stop. A third pump is also required-usually this is a DC drive pump and does not have the flow capacity of the two main pumps. Instead of a DC pump, some plants have a special lubrication tank, which is placed at a height above the turbine; thus, in case of lubrication pump failure, the tank would, due to gravity, provide the lubrication for a safe coast down of the system.