The Wenzel Hydraulic / Mechanical Drilling Jar (HMJ) is a jar designed to deliver hydraulic operation in the upward jarring direction, and mechanical operation in the downward direction. A time delay allows load variance prior to jarring up, and a safety latch mechanism to prevent unexpected jarring. The latch eliminates the need for a safety collar and special handling/precautions on the rig floor.

The Wenzel HMJ has just two oil chambers—one combined chamber for the spline drive and mechanical latch, and a second for hydraulic jarring. Fewer oil chambers means fewer seals and greater reliability. A robust metering device controls delay times across operating temperatures.

Like all Wenzel drilling jars, the HMJ has no free-moving balance piston or ports through the housing to the annulus. This keeps fluid and drill cuttings out of the tool, preventing additional wear on seals.

Feature overview

• Hydraulically activated in the up direction with impact force controlled by operator
  • Internal metering device ensures consistent delay times over a full range of operating temperatures
• Operates via simple up and down motion, unaffected by right- or left-hand torque
• Spline drive and latch mechanism enclosed in a single oil chamber without ports to the annulus
• Can be run in tension or compression within the preset latch setting
• Standard seals in the tool are effective to 250ºF (120ºC). Our hot hole seal kit is available for operation in environments up to 400ºF (200ºC)
• External sealing surfaces are tungsten-carbide coated to enhance wear and corrosion resistance.

Operation

When jarring up:

• Apply sufficient overpull to overcome latch setting; this will initiate hydraulic delay sequence. During time delay, overpull at surface is adjusted to vary impact force. Contact us for specifications on max pull load during delay.
• After impact, apply down force sufficient to close jar and re-engage latch. Repeat jarring cycle as required.

When jarring down:

• Apply sufficient downward force to overcome latch setting and pump open force. Mechanical latch will release, jarring downward.
• After impact, pick up work string to re-engage mechanical latch. Repeat jarring cycle as required.

For added flexibility, consider our HJDA or HMDA drilling jars, which can be converted to a Hydraulic Mechanical Single-Acting (HMSA) jar. The HMSA is similar in function to the conventional HMJ, but with a longer stroke adopted from the base HJDA/HMDA design. Contact a WZL representative for details.

Additionally, the Wenzel HMJ is available in Enhanced or ULTIMATE configurations:

• The Enhanced series jar (EHMJ) offers higher latch settings and a smaller pump open area to carry heavier string weight below the jar.
• The Ultimate series jar (UHMJ) provides the highest overpull capacity on the market. Using proprietary technology, the maximum allowable overpull force is dramatically increased within the design. The UHMJ can be easily converted to the HMJ design.