Bearing Test Rig Update

The TRUNNION-LATCH™ subsea connector uses the type of marine bearings that are ordinarily used on mooring system fairleads, rudders, stern rollers etc.  There are a range of providers and materials available all with varying material properties.  These bearings have already been used in hybrid riser tower systems in both Angola and Brazil.   Interestingly much of the test data for the bearings was carried out some years ago before this application was conceived.  SRP discussions with offshore operators interested in the long term integrity of riser base and air-can connectors indicated uneasiness with the existing test data.  SRP therefore decided to embark on a program of testing with the aim of replicating the actual loads, angles and cyclic motion experienced by such connectors.

Results currently show almost undetectable wear to the shaft that passes through the bearing and oscillates radially with a 137Te load applied. This equates to a bearing pressure of 50MPa which is our design load.  There is minimal non-uniform wear to the bearing sleeves themselves.  The effect of wear debris is still being investigated.

Richard Hockley, technical manager, said, “The test rig is running 24 hours a day and we are performing a strip down approximately every two weeks . So far the bearings have been performing as expected with very little wear being exhibited. We see some wear debris, which we have analysed to understand its composition.  To date we have run 195,000 cycles of +/- 20 degrees.  This is a far higher angle than would be expected in installed service so as to accelerate the results.  It equates to a travelled distance of 5.8 km.”
SRP’s award winning engineering team expects further results in May 2009.  At present SRP doesn’t intend to publish the test results which are already producing some interesting insights and pointers for further product development.