Posted on 03 January 2014
Successful testing takes CT Hang Off capabilities to new levels
LiMAR were recently approached by one of our well service clients in Brunei who urgently required a Grapple Type Connector to hang off a 2 7/8” Coiled Tubing Velocity String.
The initial brief for LiMAR’s design team was to design and test a connector capable of hanging a 60,000 lb calculated string weight, with an additional 25% safety margin in order to achieve a 75,000 lb capability.
To meet the short lead time required by the client, LiMAR’s design engineers created an initial prototype based on an existing design of a smaller connector. This prototype was fully tested and appeared to be successful until the final stage of testing where the CT slipped from the connector when applying load from 70,000 lb – 75,000 lb. Disassembly revealed that the grapple configuration had caused the Coiled Tubing to yield where the Coiled Tubing OD had reduced to the point it became free to disengage from the grapple insert. A further design evaluation was undertaken and a second prototype was manufactured for testing.
As with the first prototype, the load was applied in 10,000 lb increments with the connector being re-torqued at each stage. It was apparent at 70,000 lb with minimal slip between the Coiled Tubing and connector that the re-design was had proved successful. After achieving the required 75,000 lb working load, the decision was made to continue applying load though limit the maximum pull to 118,000 lb, 2,000 lb less than the yield of the Coiled Tubing Sample.
During the upper range of testing it was clear that the connector would not slip, nor deform the Coiled Tubing. The load was increased to the maximum agreed figure and 118,000 lb was successfully achieved. During disassembly and inspection, all components of the 3.125” OD Grapple Connector were within spec, showing no signs of deformation in any way, the Coiled Tubing did however show a negligible change in outer diameter which was recorded at 2.843”.
This accelerated design and testing program has proven a huge success. Not only did LiMAR exceed the customer’s expectations by providing a robust solution at short notice, they also successfully demonstrated their capabilities within the Insert String Market.