ICE – News no.4 (Boiler repair - Mitsubishi MCT 220)

ICE was contacted by a shipowner with a fleet of bulk carriers regarding a problem with the boiler onboard a vessel recently taken over.

The problem was leaking tubes in a composite boiler type Mitsubishi MCT 220 "Vertical water tube boiler". The boiler was classed shortly before the new owner, - our client, took over the vessel, without any remarks other than some tubes had been plugged (less than 5%). Hereby the owner wished for a second opinion of the boilers condition, whereby ICE arranged for an experienced engineer to inspect the boiler using modern technology, i.e. endoscope for internal check of tubes and ultra sonic measuring equipment for material thickness measuring.

The inspection revealed major corrosion problems in a rather limited area of the tube bank, initiated from cracks developing from fin welds to the tubes forming the vertical (centre located) furnace of the boiler. The cracks have caused leakages resulting in continuous moistening of an area inside the tube bank not visible from inspection / cleaning doors and was only revealed by the use of endoscope allowing to visually check the condition in between the tubes.

The largest problem for the owners were that the vessel just entered a new charter not allowing any off-hire within reasonable period without major economic consequences. The boiler of composite type includes an exhaust gas fired section in combination with an oil fired section, normally not allowing opening and repairing the boiler with main engine in operation.

Due to the experience of ICE from previous repairs to this and similar boiler types we proposed a solution to the owners where a by-pass was erected for the exhaust gas from main engine. This will allow running the engine without the gas entering the boiler. During the period of repair, the vessel was to be operated on MDO, which is more costly than HFO, - but compared to off-hire it is still a much more profitable solution.

The repair schedule was carefully planned by ICE and approved with vessels classification society ClassNK in Singapore where the repair was also commenced after shipping the necessary spares, tubes and special tools.

The full retubing of the boiler was carried out by one of ICE's highly skilled and professional teams of boilermakers, without any delays to the vessels schedule, other than planned for erecting and dismantling the exhaust gas by-pass necessary to carry out the repair in this way.

We are proud to say that this repair was only possible due to the professionalism and enthusiasm of our repair team, as the conditions under which the repair was carried out was during more of the time quite inhuman with temperatures at the work site reaching more than 80 degr. celcius on the metal surfaces.

The repair of this boiler type during vessels sea voyage was chosen only as a "last option" in order to save costly off-hire of the vessel, and the repair was completed as scheduled in the contract, with major savings for the owners compared to a traditional repair with vessel being idle.