The Suntec E1069 Series pumps are designed for use Heavy Oil. They are suitable for use with a one or two pipe system and are usually used with an in-line solenoid valve. The shaft seals on the E1069 pumps are designed to resist high temperatures, there is also a drilling to allow for the installation of a pre-heater.
During starting period when the gear-set speed is increasing, all the oil passes through a special flat on the piston, back to the return. Once the speed reaches a certain value and the flow can no longer pass through this flat, then the pressure increases rapidly overcoming the valve spring force and opens the valve. During the stop sequence, the gear-set speed slows down and the valve closes when the gear-set capacity is lower than the flat flow.
Rotation of these pumps is determined by viewing the pump from the shaft end.