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17th December 2014

Improvements have been made to the Hard Driver®, Sling Shot®, Flow Release Overshots, Double Flapper Check Valves and the Grapple Connectors to name but a few. The intention of this article is to highlight the improvements which have been made to some of the more commonly used items, namely the Motorhead Assembly (MHA), the Hydraulic Disconnect and the Heavy Duty Disconnect.


In Q2 2014 LiMAR® launched the 10,000 psi MHA, an enhanced redesign of the original 5,000 psi rated tool. Through customer demand the design and development of a 15,000 psi rated tool followed suit and was launched in Q3. Both tools feature single piece check valves which not only improve the working pressure potential but allowed a larger through bore. The 10,000 psi rated tool was released with no reduction in the MHA internal diameter or drop ball size, however, to achieve a 15,000 psi working pressure tool some modifications were necessary. To ensure that the tool remained H2S compatible alterations were made to the wall thickness which resulted in a slightly reduced internal diameter.


  • Relocated o-ring grooves from the OD of the upper body to the ID of the lower body to improve resistance to side loading and vibration, which also provided a significant increase in tensile strength.
  • Increased hydraulic surface area in the disconnect section to encourage the tool to separate without applying tensile load.
  • Slots were introduced to the shear piston to prevent the accumulation of slurries below the shear piston.
  • Flow area from the circulation sub was increased to minimize back pressure and maximize flow rate to aid removing debris from the well-bore in stuck pipe scenarios.
  • Optional Ball Seat Retainers were designed to permit circulation through the MHA after shifting the shear piston and prior to picking up to separate the tool. (An important function in situations where the work-string is stuck above the BHA and debris may need to be dissolved or circulated from the well-bore).


With notable improvements in tensile strength and resistance to sideward loading made to the MHA, LiMAR® Engineers then applied the same concepts to the Hydraulic Disconnect. With all designs complete, calculations performed and the results confirmed using Finite Element Analysis software, the outcome was an H2S compatible tool with a higher tensile safe working limit than the current revision of the non H2S compatible Heavy Duty Disconnect. It was clear that the next step in the product evolution was to improve the tensile rating of the Heavy Duty Disconnect (HDD).


The capabilities of the existing Heavy Duty Disconnect would not allow the drop ball to be returned to surface with the upper half of the BHA. With a new version of the tool to be designed the brief was clear.

  • Increase the tensile rating
  • Ensure the drop ball could be returned to surface following a disconnect
  • Improve resistance to shock and side loading
  • Design a tool which is less susceptible to failure, or premature disconnecting under heavy jarring loads


Following months of planning and testing the new Heavy Duty Disconnect has been developed with improved tensile strength, a ball seat retainer which allows the drop ball to be returned to surface and a shock absorbing shear piston which further reduces the likelihood of premature disconnect under abnormal jarring loads or extreme vibration. New revisions of all tools are now available in 1-11/16”, 2-1/8”, 2-7/8” and 3-1/8” sizes as standard, other sizes are available on request. Please download the product sheets: Heavy Duty Disconnect 10,000 MHA 15,000 MHA or contact sales@limaroiltools.com should you wish to receive further information on any of these products.



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