The HMJ incorporates a latch mechanism to keep the jar locked in the neutral position and eliminate unexpected jarring while tripping or racking on the derrick.

The built-in mechanical latch keeps the jar locked in a neutral position, which prevents stroking of the jar downhole and unintentional firing of the jar while drilling or tripping. When latched, the mandrel and housing act integrally, eliminating seal and inner-tool wear. The latch eliminates the need for a safety collar and special handling/precautions on the rig floor.

The hydraulic valve provides delay when jarring up, allowing drillers to vary overpull and control impact force. The valve resides in its own oil seal chamber for increased reliability, and a robust metering device controls delay times across operating temperatures.

Down strokes use the mechanical part of the jar, while upward strokes use the hydraulic part with hydraulic delay. The mechanical latch actuation force can be adjusted and set during the jar assembly upon customer request.