This device is seat sealed by hydraulic differential pressure and self-locking, and packer released by safety pin in locking assembly forming tubing-casing connection.
In normal production, liquid produced from oil well, through screen liner (also called bell mouth) and the center pipe of the well washing machine, flows into the oil casing annular space which located above well washing machine and the pump. Then the liquid is discharged into surface flow.
In well washing process, washing liquid flows into the oil casing annular space. At the moment, seat seal plastic bowl opens while the inverted valve on the center pipe closes up. In this way, the leak-proof well washing machine prevents the leaking of washing fluid into formation, thus achieves the aim of leak proof well washing.
When wells are washed by feeding drugs, mixing oil and mixing liquid, for general wells the leakproof well washing machine can reduce the drug and blending liquid amount. While for leaking wells, it can prevent washing liquid (liquid dosed or oil blended) from leaking into the reservoir, reduce washing liquid amount, decrease well washing cost, improve well washing effect, reduce the pollution of washing liquid to the reservoir and finally achieve the aim of protecting the reservoir.
In the operation of pump detection and workover, when the oil pipe is lifted, well washing machine under the pump rises following the oil pipe. Owing to the combined action of friction and hydraulic pressure produced by the storage of liquid in annular space over the device on the seat seal plastic bowl, the center pipe of the well washing machine shifts down, then the unsetting pin snipped. As the oil pipe continues to be lifted, the related center pipe of oil drain sliding sleeve on the leak proof well washing machine shifts down, as a result the spill port is opened. The opening of the spill port connects the annular fluid above and shaft liquid under the well washing machine. This way guarantees the impollution to the well site.
In reverse well washing, when the pump pressure reaches a certain value, the unsetting pin is snipped under the action of well washing pressure; The shift down of seat seal plastic bowl and unsetting joint opened the spill port. The opening of the spill port realizes the connection of washing liquid above and shaft liquid below the well washing machine.

2. Main Characteristics
1. In pump's normal production, leakproof well washing machine doesn't affect the dynamic recovery and test.
2. In well washing or liquid blending, leakproof well washing machine effectively prevents from leaking.
3. In pump detection and workover, leakproof well washing machine can lead the liquid above flow into the well, thus prevents washing liquid from polluting the well site.
4. Leakproof well washing machine can eliminate the wear between sucker rod and oil pipe, the wear between piston and liner owing to the creep of the string when pump unit is working. Consequently it can enhance the pump's work efficiency and prolong pump's service life.