On-Site Repair In North Sea
In-situ machining Solutions (UK) Ltd have very recently, at the request of a major rotating machine company completed the repair to a large centrifugal fan shaft bearing diameter used for hazardous area ventilation situated in one of the most northerly oil fields in the North Sea.
Removal of the impeller/shaft assembly for onshore repair was not viable due to the assembly being too large to be removed from it’s casing and the fan room which housed three of these fans. The work, therefore, had to be carried out on site, offshore, where severe climatic conditions only allowed work to be carried out in three hour stretches at a time.
Damage to the 80mm x 220mm long diameter fan shaft was due to the bearing’s split adapter sleeve turning on the shaft during the fan’s operational speed of the 750 RPM causing extensive circumferencial grooving approx 2mm deep.
The solution was to orbitally machine and polish the shaft to 75mm diameter and to shrink fit a make-up sleeve of 2.5mm wall thickness onto the shaft enabling the shaft diameter to be brought back to the original 80mm diameter.
A series of roughing cuts were taken along the shaft initially, followed by a finishing and polishing operation prior to shrinking on the pre-made make-up sleeve.
An allowance of 0.5mm was left on the outside diameter of the make-up sleeve for finally machining and polishing the 80mm to the limit size requirement to allow the fitting of a new split spherical roller bearing arrangement.
Due to limited radial access to the shafting the In-situ design team produced a special small series orbital turning machine, associated attachments and tooling to add to it’s extensive standard range of larger machines.
All work was carried out in conjunction with our customer’s and the end user specification, inspected and passed of to their satisfaction, prior to the team’s demobilising from site.
