The invention discloses an automatic underground sand bailing device and a sand bailing process thereof. According to the device, a steel
wire rope is used for driving a sand bailing pump to move vertically for realizing automatic sand bailing. A
rope guide wheel is coaxially provided with an
angular displacement sensor for detecting the length of the steel
wire rope. A fixed
pulley base is provided with a load sensor for detecting the load of the steel
wire rope. A sand loosening hammer and a valve plug of a sand
inlet valve at the bottom of the sand bailing pump are of an integrated structure. The steel wire
rope is connected with a
rope ring on the top of a weighted
piston rod, so as to drive a
piston to move vertically in a walking cavity between the sand
inlet valve and a sand carrying valve. When the
piston moves downwards, the upper part of the walking cavity forms negative pressure, and sand carrying well fluid on the lower part of the walking cavity pushes to open a
check valve in the piston and enters the upper part of the walking cavity. Before the piston touches the bottom
dead centre while moving downward, the piston moves downward slowly so as not to
impact a bottom
dead centre. Before the piston touches the top
dead centre while moving upward, the piston moves upward slowly so as not to
impact the top dead centre. The automatic underground sand bailing device and the sand bailing process thereof have the advantages that simplicity and reliability are realized, the pump efficiency is high, the degree of
automation is high, the piston is effectively prevented from impacting a top dead centre and the bottom dead centre, and the device and the process are particularly suitable for low-liquid level oil-
water well sand bailing.