A winch manufacturer was seeking for solutions to enlarge and deepen bolt holes on its supplied turret riser winch to increase the permissible heave in torque by request from the turret designer. As the winch is already housed on board an operating FPSO at Brazil’s offshore oil field, no hot work such as welding, gas cutting or lashing is allowed and therefore more engineering efforts have to be input in ensuring the success of the modification on the winch.
The modification of the winch involved stringent technical requirements; the bolts holes at the drum body had to be enlarged from M36 to M42 with running fit tolerance Ø43mm (+0.025/0.00) and as the bolt holes are orientated at horizontal position, the tight tolerance for both perpendicularity and straightness of the new thread holes are not possible to achieve using conventional portable tooling. Another delicate work scope is to machine and enlarge the inner pipe shaft with a tolerance range from 0.00mm to 0.057mm.
Metal Machines was call in by the turret designer to angle for a suitable engineering methodology for the restrictive site’s conditions and imperative job tolerance.
To illustrate the proof of concept, the team from Metal Machines constructed a 1:1 test model to prove the feasibility of the proposed approach by the usage of a customised jig and fixture together with a set of Climax BB5000 for the high precise drilling and boring processes.
The demonstration and results were endorsed with the presence from both winch manufacturer’s representative as well as the turret designer’s representative which included the test and inspection plan derived according to the engineering procedure.
The work scopes for the modification of the winch was completed by the site team within 2 weeks on board the FPSO.
The site team from Metal Machines was able to coordinate closely with the ship crews on the time and operation management to avoid causing unnecessary downtime for the FPSO.
With reiterate of process walk through and prudent planning, the site team was able to execute the job beautifully and receive high compliment from the client.