Shiprepair & Maintenance: 1st Quarter 2021
Denmark’s MarineShaft has got off to a flying start this year with a number of significant projects being undertaken at its Hirtshals workshop in the early part of 2021. This January, two CPP hubs were repaired using the company’s laser cladding techniques, while a cylinder head was given a new lease of life after laser cladding of valve seats.
Two sister vessels were undergoing a planned overhaul at a shipyard in Europe, and the owners requested that MarineShaft repair the CPP hubs. Seal areas on the propeller hub needed repair due to wear, and the company applied two layers of bronze material, each layer being 0.8mm thick, followed by the necessary machining after the laser cladding.
Along with the two hubs, MarineShaft received eight new bearing bushes for this project. The inner diameter of each bush was machined to the required final dimension and both the hub and bush were fitted together before the components were returned to the yard to complete the overhaul.
Hanne Magnussen, marketing manager, says: “There are a number of advantages of using laser cladding for cylinder hub repairs. This includes the fact that the bronze binds 100% to the base material. Moreover, because laser cladding involves a minimum of heat input, it does not disrupt the base material.”
Cavitation under cylinder head valve seats is a common problem and this was the case for another repair carried out by MarineShaft this January. The tolerance of two cylinder valve seats could no longer be maintained, even with a valve insert, and the solution was to either replace the units or rebuild by laser cladding. With the owner opting for the latter option, MarineShaft rebuilt the seats to the original dimensions using its laser equipment.
Magnussen adds: “We applied three layers of Inconel 625 followed by machining to the original size. This repair has prolonged the service life of the cylinder head quite substantially.”
MarineShaft’s experience of using laser cladding is relatively recent as it invested in its first laser equipment only in 2017, but already it is a well-established and much valued tool to meet customer requirements for effective and long-lasting repairs. “The repair options and benefits of laser cladding are far greater than we first assumed,” says Peter Pallesen, senior project manager at MarineShaft. “We can rebuild and repair wear and cavitation on items that would otherwise often be discarded.”
He continues: “Applying a stainless material on, for example, an ordinary steel shaft increases the wear resistance of the shaft and thereby its life expectancy. Based on our successful experience over the past few years, we are now using our laser equipment on a wide range of vessel components, including propeller shafts, propeller shaft cones, bearing journals, couplings, and engine parts.”
To support the use of laser repair techniques, MarineShaft now has a number of tools and equipment that can be used for on site and in-house repair tasks. The company has recently built a new mobile carousel type unit, which makes it easier to use the laser equipment on larger items such as propeller hubs and gears. The mobile unit was in fact used to good effect on the recent CPP hub project.
In order to keep pace with demand for its propulsion system repair services, MarineShaft is currently expanding one of its three workshops in Hirtshals to further boost capacity. Its Silverveg facility is being almost doubled in size from 1,600 to 3,000m², while additional equipment will be installed to increase lift capacity from 1000 to 2,000tonnes. The expanded workshop will house a newly acquired 35m lathe and an 8,000tonne hydraulic press that can cold straighten shafts up to 1.5m diameter. The expansion work is nearing completion and the new area of the workshop is expected to be operational within the next few months.
