WHat is a drilling Jar?

[mbchuks]

Pls can anybody explain in clear unambiguous terms what a Drilling Jar is. Thanks in advance.

[pramodkumar1990]

Drilling Jars
The rig crew installs a drilling jar in the drill string if there is a concern of becoming stuck. Drilling jars are usually made up on the upper part of the bottom hole assembly with drill collars placed above and below the jars. When activated, a drilling jar provides a heavy blow to the stuck portion of the drilling string below the jar. Often the blow delivered by the jar is enough to knock loose the stuck string.

Drilling Jar Operation
To create a jarring blow up with a hydraulic jar, the driller lowers the drill string to cock the jar. Then the driller applies an upward pull. The upward pull puts the up jar in tension and allows the jar trip mechanism to slowly bleed. Eventually, the jar trips when the hydraulic oil bleeds past the ports. The drill string contracts, rapidly accelerating the bottom hole assembly above the jars. When it reaches full stroke, the jar mechanism suddenly stops the motion energy of the string. When the motion suddenly stops, it converts the kinetic energy (or energy in motion) into impact force on the stuck point. This heavy upward blow may free the stuck string below the jar

source from schlumberger drilling cd volume 1

[markspend01]

Hey Guys well i think that the jar is a mandrel which slips within a sleeve. The free end of the mandrel is formed by means of a sort to offer a stunning activity against the experience of the anvil.Thanks!!

[9september]

[link Point to another website Only the registered members can access]
This might help.

[9september]

[link Point to another website Only the registered members can access]
This might help.