Recently, Maritime Propeller Repairs BV, an affiliate of the S-T Diesel and Marine Group, carried out an extensive repair job on a fixed pitch propeller in Cadiz, Spain. The work was done for the “MV Barry”. The work involved the repair of all five blades, three of which required the forging of brand new blade tips (1000 kg each). The new tips were cast in MPR’s Drunen foundry (Gieterij Drunen), and were then transported to Cadiz, Spain.
After a meeting with the shipyard manager, it was decided that the propeller would be repaired in the cargo hold on the vessel. The yard had erected a tent for the purpose; however, it was susceptible to interference from strong winds and changes in temperature.
On the same day, the inspection and measurement of the two whole blades which required repair was carried out. Blade 2 had a bent area of 700 x 250 mm, and was missing a piece 350×90 mm of area through corrosion and wear. Blade 3 had a bent area of 850 x 200 mm, and was missing 360 x 160 mm. The edges of the blades were cleaned before repair, and the dye-penetrant tests of all edges and blade roots were also carried out. A dye penetrant test of the blades and blade tips will identify any cracks that may not be visible with the naked eye.
On Sunday, MPR engineers carried out preparation of welding grooves and polished off the pressure side of the propeller, and on Monday the propeller was transported to the cargo hold of the vessel after many delays. Argon, propane gas, oxygen, electricity, air and hoses all had to be arranged to be accessed from the cargo hold.
A couple of days later, the welding of the blade tips began, as well as the straightening of the two bent blades. When the welding of the blade tips on the suction side was complete, the propeller was raised and turned to the pressure side. This side then required the same process of grinding and a dye-penetrant test before welding could begin. The blades were pre-heated, welded, and then measured from the pressure side.
During the stress-relieving process that follows this, the blades are wrapped in thermo blankets and kept at a set temperature by a control unit, and once again, grinded and polished to ISO class 1.
Upon completion, the propeller repair was approved by DNV-GL.