Propeller Shaft Line Work on New ULCS

After we have in an earlier post looked at some recent two-stroke main engine crankshaft repair assignments that we have carried out on ships in operation, we now move the focus further towards the after end of the ship.

In this post we look at how we routinely support new building shipyards with shaft line alignment and machining work.

Read more about our recent two-stroke crankshaft work assignments

Read more

Shaft Line Work for VLCS in China: Recent Success Stories

At QuantiServ, we routinely perform essential alignment and machining work on behalf of shipyards in China on new vessels under construction. We do this for a wide range of vessels.

In this post we look at some of the very largest vessels that we work on, namely Very Large Container Ships (VLCS). These are vessels with a capacity to simultaneously carry up to 24’000 standard, 20-foot shipping containers. Typically, these ships are 400 meters long, about 62 meters wide and have a draught of about 16 meters when fully loaded.

These colossal vessels typically feature shaft lines that span between 80 to 100 meters in length, with shaft diameters ranging from 900 mm to over 1000 mm. These impressive dimensions are imperative due to the massive power of these ships’ main engines, which can reach up to 60,000 kW. This is equivalent to the power of 600 average-sized cars.1

Case 1: Stern Tube Bearing Failure Recovery

In one notable project, we assisted a shipyard and shipowner after a stern tube bearing failure on a recently delivered VLCS. While underway, the ship’s stern tube bearing suddenly overheated, reaching temperatures of well over 200 ℃, leading to the complete destruction of the bearing bush. The sudden heat increase also led to cracks in the propeller shaft.

Obviously, this critical issue required prompt action to prevent extensive downtime. Our team efficiently assisted the shipyard to replace the bearing bushes and machined the shaft in-situ to remove the cracks in its surface. Our ability to machine the shaft in-situ eliminated the need to withdraw it, which would have been a time consuming and risky operation. This approach thus not only saved valuable time and therefore minimized operational losses. It also reduced the risk of anything going wrong during the delicate propeller and shaft removal and reinstallation work and  ensured that the vessel could return to service swiftly.

After completion of our work, the shaft bearing temperature was recorded at just 32 ℃, no more than 13 ℃ Celsius above the surrounding sea water temperature, which is an excellent result!

Shaft alignment check by laser
Shaft alignment check by laser

Case 2: Construction Phase Alignment and Line-Boring

During the construction of another VLCS, our laser alignment checks revealed that the newly delivered and installed stern tube suffered from ovality and incorrect slope, posing a significant threat to the vessel’s long-term, safe performance. Once our team brought this information to the attention of the shipyard and proposed to line bore the stern tube, the shipyard, classification society and shipowner quickly agreed to our solution.

By employing precise in-situ line boring techniques, we corrected these issues, ensuring that the ship’s shaft line  will perform optimally for many years to come. This intervention during the ship’s build phase highlights our commitment to quality and foresight.

Case 3: Long-standing cooperation

QuantiServ has long been a trusted partner for shipyards worldwide. We are often involved from the early stages of new-building projects, providing technical expertise and precision machining services. For example in China we have ongoing agreements with several major shipyards, whereby we carry out laser alignment and inspection services for entire series of vessels.

During the summer of 2024, we for example completed shaft alignment services for the sixth and final delivery in a series of large, LNG-fueled ships built for a major container shipping line. All six ships are now in operation and are performing very well.

Demonstrating Expertise Across the Industry

All three cases were undertaken in China on some of the worlds’ very largest and newest ships, that will be owned and operated by three of the world’s largest container shipping lines. They involved different shipyards and different classification societies. This diverse customer base underscores the broad acceptance and trust in QuantiServ’s expertise and know-how within the maritime industry.

The three ships highlighted in this post are all either LNG-powered or are able to operate on more than one fuel. As such, they contribute to the decarbonisation of the marine industry, which is a goal that QuantiServ very much supports. Furthermore, QuantiServ is proud to contribute to the reliability and efficiency of these magnificent vessels, ensuring they meet the highest standards of operational performance and safety.

A severely damaged stern tube bearing bush
A severely damaged stern tube bearing bush
Machining the outer circumference of a stern tube bearing bush
Machining the outer circumference of a stern tube bearing bush
Stern tube line boring
Stern tube line boring
Delicate, ctitical work creates a lot of attention
Delicate, ctitical work always creates a lot of attention
Calibrating the outside diameter of the bearing bush
Calibrating the outside diameter of the bearing bush at our workshop in Shanghai
Inspection of a large stern tube bush at the shipyard
Inspection of a large stern tube bush at the shipyard

1 In 2018, the most recent year for which data are available, the average car in the European Union was fitted with an engine that was able to produce 98 kW of power.

15’000 TEU Container Ship Intermediate Shaft In-situ Machining

Our colleagues from QuantiServ Shanghai have just completed an intermediate shaft repair assignment on a 15’000 TEU container ship.

While underway to a southern Chinese port, the almost new vessel had suffered a breakdown to one of its line shaft bearings. Running steel to steel as a consequence of the bearing failure, the intermediate shaft got severely damaged.

QuantiServ Shanghai got contacted while the vessel was on tow to one of Chinas largest shipyards in the greater Shanghai area.

Our experts immediately got to work and presented to the shipowner and shipyard a repair plan and schedule, before the vessel even reached the shipyard. The plan included the re-design of the line shaft bearing, the design and fabrication of special in-situ machining tools and the execution of the work in three shifts, around the clock. All stake holders agreed to the plan.

Once the tools had been fabricated, our technicians performed the following work on board the vessel, while alongside in the shipyard. Some of the tasks had to be carried out multiple times, for example laser alignment checks before, during and after machining.

  • Laser alignment checks and alignment calculation
  • Dimensional and hardness measurements, non-destructive crack testing
  • Removal of cracks, shaft journal area machining to under-size, then polishing
  • Shaft alignment adjustment
  • Bearing load jack-up tests

Our six technicians performed the work in two shifts, around the clock. The entire repair took just seven days to complete to the full satisfaction and appreciation of the shipowner, shipyard, classification society and shaft line bearing OEM.

 

Key data of the installation:

  • Intermediate shaft total length: ~ 39 m
  • Shaft diameter: 790 mm
  • Shaft journal length: 1’200 mm
  • Max continuous engine power transmitted through shaft: ~ 53’000 kW
Intermediate shaft in-situ machining
In-situ machining (cutting)
Measuring of the diameter
Measuring of the diameter
In-situ polishing
In-situ machine polishing

Comprehensive Repairs: We Succeed Where Others Fail

Example of a Comprehensive Crankshaft Repair Assignment, Started and Then Abandoned by a Competitor

During the last days of 2020, our in-situ repair specialists out of Gothenburg, Sweden, repaired a damaged crankpin on a Korean-made four-stroke engine. The engine has a 32 cm bore and a 40 cm stroke and is installed on a 5 year old, 9’200 TEU container vessel.

When contacted by the ship owner, we proposed to carry out an inspection on board. The shipowner agreed, whereafter our specialist from QuantiServ Panama carried out a thorough inspection in Panama. To our disappointment, the ship owner then awarded the repair work to another company. Their technicians machined the pin to – 0.80 mm undersize and then gave up and disembarked from the vessel.

Finding himself in a tight spot, the customer came back to us and asked us if we could continue the repair that was abandoned by the other company. We took the opportunity to demonstrate that we succeed where others fail. Two in-situ specialists from QuantiServ Sweden joined the vessel and successfully carried out the repair work while  underway from Lima, Peru to Manzanillo, Mexico. They solved the problems as follows:

Issue Action taken Result
Damaged surface and cracks Machining Crankpin under-sized to – 3.00 mm
Excessive hardness Heat treatment (Annealing) Hardness Reduced from 620 HB to 255 HB
Bent crankshaft Peening Run-out reduced from 0.27 mm to 0.03 mm

The customer was very happy with the skills and performance of our specialists. He therefore kept them on board for subsequent reassembly and overhaul works and he also asked us to supervise an  overhaul of a similar engine installed on a sister vessel.