DOUBLE ACTING HYDRAULIC-MECHANICAL DRILLING JAR

● Up Jarring

Lower the drill stem to ensure that drilling jar is closed completely (in locking  position). Up jarring is achieved by slowly increasing the lifting force on the drill  stem, until there is sufficient pull force to overcome the spring resistance and  initial hydraulic time delay. During the time delay, the overpull at surface can  be adjusted to vary the desired impact force. When the mandrel reaches the  trigger position, there is a sudden release in resistance, the elastic potential  energy stored within the drill string will be transmitted to forward up jarring  impact energy. After impact, apply a downward force sufficient to close jar in  locking position, then repeat the jarring cycle as required.

● Down Jarring

Lift and lower the drill stem to ensure that the drilling jar is closed completely  (in locking position). Down Jarring is achieved by applying sufficient downward  force to compress the spring and store elastic potential energy. When the  pressure of the jar is greater than the desired unlocking force, the grapple will  slide away from the mandrel to release the locking, performing down jarring  action. Repeat the procedures to produce continuous down jarring action