دیکشنری تخصصی مهندسی نفت - نسخه آنلاین

n: a device made up in the drill string that, when actuated, de- livers a heavy downward blow to the string. A bumper jar has a hollow body that moves upward when the drill string is picked up. When the string is dropped quickly, the jar body produces a sharp downward blow on the tubing or pipe made up below the jar. If downward blows can free a fish, a bumper jar can be very effective.

n: Made by upwardness, lower part of the body and joint. The upwardness and lower part of the body are connected with plain bearing. The operating principle of it is the same with bumper sub. Used to handle sticking when the drill bit is not at the bottom.