Anti-loop magnetic devices and magnetic salvage salvage salvage device is the well can be magnetized metal debris of a tool. Hard formation in the salvage effect is remarkable.
Structure and principles:
Salvage device according to the type of magnetic force into a permanent magnet type and magnetic-type charge; by cycle salvage divided into common type and anti-recycling. It consists of shell, magnet, magnetic milling shoes and nursing boards. Salvage device outer tube is made of high permeability, low coercivity magnetic materials made of. Core through the upper ends of the magnetic field lines form magnetic field lines and shell access, can be seen as a shell and milling shoes made by the magnetic pole as a ferromagnetic jacket; permanent core of the bottom of another pole. In the middle of milling shoes with non-magnetic core material (copper) isolation to prevent short circuit. Salvage, the litter of the two magnet poles take the pass, so firmly adsorbed on the magnetic bottom fishing
Magnetic device is a positive cycle of salvage; salvage anti-magnetic device pitching circle before the positive cycle, after pitching into reverse circulation, flow around the pieces to help the bottom rail toward the borehole center will help salvage the scrap iron from more. Magnetic salvage salvage device and counter-cyclical device using magnetic methods are the same, except that the latter need pitching, is to salvage as an example of reverse circulation magnetic as follows:
(1) magnetic salvage device should be selected according to borehole diameter.
(2) milling the choice of shoes according to underground conditions.
① flat shoes: it's bottom end with the core in the same plane, in contact with the whereabouts of large area well, so suction is also large, litter size for the number of large and more widely distributed, but that had been pressed into the formation of metal debris are powerless.
② call shoes: with a higher core litter the bottom of the dial is used to toggle shoe ring for litter to be stuck or pressed into the cake bottom of debris salvage.
③ mill shoe: it has a core base of the mill shoe above the ring for caliper irregular or cone-shaped hole, the core can not reach things off the situation, it can be milled hole and litter.
(3) go down the suction should be checked before, appearance, eye screw and water conditions. Magnetic salvage device should be connected on the board, shall not be salvaged for direct magnetic turntable or other metal objects sitting on the surface, not violent shock, in order to avoid loss of field.
(4) salvage magnetic devices away from the litter down to 2 to 3 m open-loop drilling fluid pump. Rinse until the bottom (bottom grit determine whether or not rinse the salvage effect), put on a pitching drill pump stops. Decentralization of drilling from the bottom to open the pump of 0.5 meters, cycle for ten minutes, and then guide shoe type, take different measures to salvage. When using flat shoes must be delegated the slow side circulation drilling to bottom edge (note: not more than 9.8 kN WOB, can only prove in the end), then put on the drill 0.3 to 0.5 meters, then the direction of rotation decentralization of drilling, so that repeated several times, check into the side, that may have been purely monetary litter from drilling.
When using dial shoes, while cycling up and down while intermittently rotating and drilling activities, when the salvage device contact with litter magnet rotation when the drilling ban to prevent damage to the core. Then put the edge of edge loops 0.3 to 0.5 meters, can be repeated several times since recovered drilling. When using milling shoes, methods of operation and allocation of shoes, except that the continuous rotation into intermittent rotation. Salvage in soft formations, should pay special attention to rotation and the depth of decentralization added WOB, pressed into the ground to prevent the failure of the salvage.
(5) magnetic charge and magnetic devices under salvage and, it must give the core magnetization, and pay attention to polarity of charge, shall not be reversed.
(6) parking, the cover protecting the magnetic board. Be careful not to short circuit the poles of ferromagnetic material will be.