KXJ type bumper sub is a mechanical jarring tool. It allows operators to bump up or down repeatedly until the fishing objectives are met or when the stuck drill stem is released. In event where stuck drill stem cannot be released by lifting and jarring, the bumper sub can be rotated to engage and disengage releasable fishing tools to release the fish. In milling and cutting operations, the bumper sub is used to provide feeding force to the mechanical internal cutter, ensuring a reliable and even cut. When the bumper sub is used with a reversing unit, it helps to compensate the rising stroke for threads after reversing.
Working mechanism
● Energy conversion in jarring operation
Downward jarring forced is achieved through the conversion of stored energy to kinetic energy. When lift load is applied to the drill stem, the bumper jar is pulled open to a certain height creating a potential energy. As more lift load is applied, the drill stem begins to accumulate stored strain energy due to the spring extension. Sudden release of the lift load will convert the stored strain energy in the drill stem to a downward acceleration force. As the drill stem accelerate downwards, the bumper jar is released towards its closed position, releasing its potential energy. At this instant, both released energies combine, creating a large downward jarring force.
● Main factors that influence the jarring force
Hanging weight on top of drill stem with the bumper jar. Higher hanging weight will create higher jarring force. Length of spring extension of the drill stem.
Longer length of spring extension during lifting will provide a greater jarring force.
Stroke length of the bumper jar. Longer stroke length will provide a bigger jarring force.
