line boring Archives

Propeller Shaft Line Work on New ULCS

21st November 2024

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

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!

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

Machining the outer circumference of a stern tube bearing bush

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 at our workshop in Shanghai

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.

Very Extensive Crankshaft and Block Repair on a Passenger Ferry

5th November 2024

Overview

QuantiServ recently completed a large-scale repair assignment on a passenger ferry. The ferry was built in the year 2000 and is equipped with four 12-cylinder, 46-bore main engines, with a nominal power output of 12.6 MW each.

In early 2024, two of these engines required extensive repairs, having each accumulated over 120,000 running hours and having suffered a recent failure.

QuantiServ was contracted to carry out the repair of both engines. As additional defects were found during the repair, the work turned into a sizeable project that took almost four months to complete.

Our in-situ machining specialists from Sweden carried out all work during the winter months of 2023/2024, while the vessel was out of operation during the low season.

One of the two crankshafts was removed from the engine and underwent repair on the vessel's car deck.

Damage

The following damages were found. They were all addressed by our specialists during the repair.

Engine Number 1

Crankpin bearing failure
As a consequence: Multiple cracks, excessive surface hardness of 600 – 680 HB

Engine Number 2

Failure of four crankpin bearings
Crankshaft bent
Failure of one adjacent main bearing
A collapsed main bearing saddle, as a consequence of the heat generated
Poor fitting of another bearing saddle
Severe cam effect on all other crankpins

Multitude of cracks in the crankpin journal — After cutting off some material from the crankpin, a multitude of cracks became visible. They were caused by the rapid temperature raise and fall during the bearing failure.

In-process hardness measurement during machining. The areas with increased hardness are easily visible. — In-process hardness measurement during machining. The dramatic temperature changes resulted in changes in the local microstructure that are easily visible.

Surface hardness of up to 680 HB following the failure. The acceptable limit is 300 HB. — Due to excessive heat generated by the failed bearing, the surface hardness had increased to 600 - 680 HB. The acceptable upper limit is 300 HB.

Detailed Work Performed

All repair works was done while the vessel was berthed during low season.

Engine Number 1

Crankshaft Repairs:

Heat Treatment and Machining: One crankpin was machined to an undersize of -3.00 mm.
Polishing: Two main bearings were polished to ensure smooth operation.

Engine Number 2

Due to damage found on the engine block, the crankshaft was removed so that line boring on the block could be carried out. Heat treatment and in-situ machining on the crankshaft was carried out on the vessel’s car deck.

Crankshaft Repairs:

Heat Treatment: Four crankpins and one main journal underwent heat treatment.
Machining: The treated components were machined to undersize diameters ranging from -2.00 to -5.00 mm, depending on their condition.
Straightening: The crankshaft, found bent with a run-out of 1.50 mm, required peening (in-situ straightening).
Polishing: All main journals and crankpins, exhibiting strong indications of the “cam effect,” were polished.

Engine Block Repairs:

Bearing Saddle Realignment: The overheating of one main bearing caused misalignment, necessitating the replacement of the bearing cap and subsequent line boring.
Bearing Cap Adjustment: Another main bearing cap showing a gap with the cylinder block was corrected.

Additional Improvements

In addition to the primary repair tasks, QuantiServ addressed machining work previously carried out by another company on some of the crankpins. The fillets were not nicely cut, and the radius around the oil hole needed improvement. Our specialists refined these areas, ensuring optimal performance and longevity of the crankshafts.

Summary Table of Work Done

Engine	Work done
# 1	Heat treatment and machining to -3.00 mm undersize of one crankpin
	Polishing of two main bearings
# 2	Removal of the crankshaft for external heat treatment and in-situ machining
	Machining to undersize diameters of -2.00 to -5.00 mm
	Peening (in-situ straighening) to correct a bent crankshaft with 1.50 mm run-out
	Polishing of all main journals and crankpins
	Replacement of a bearing cap and line boring due to misalignment
	Adjustment of a main bearing cap gap with the cylinder block

One of totally five crankpins that our specialists machined to under-size

The mirror-like finishing on one of the crankpins. — Impressive, mirror-like finishing after polishing of the crankpins.

Conclusion

This extensive in-situ repair project on a passenger ferry highlights QuantiServ’s expertise and ability to perform critical repairs without interrupting service.

The phenomena known as “cam effect” or “ridge wear” could be identified as reason for the bearing failures and the ensuing, rather extensive and therefore costly, repairs. It is therefore very important that ship owners and operators are sensitive to this issue and regularly check the condition of the crankpins once their engines have surpassed aproximately 60,000 running hours.

Has your four-stroke engine accumulated around 60,000 running hours or more?

Although the crankpins might appear to be in good condition, it is very likely that they suffer from the cam effect (also known as ridge wear) and are in need of machine polishing. If this is not done, then you might face a failure soon!

Line Boring of a Locomotive’s Diesel Engine Block

10th November 2023

Our in-situ machining specialists recently carried out line boring of the main bearing pockets on a 20-cylinder, two-stroke engine. The engine is installed in an American-built diesel-electric locomotive and operates in Scandinavia.

Line boring became necessary due to the seizure of three main bearings. We performed the repair work in our workshop in Gothenburg, Sweden.

We routinely carry out line boring on all kinds of diesel and gas engines, mostly on main bearing and camshaft bearing pockets, or to install sleeves to stop water leaking along the cylinder liners into the oil sump.

This particular job stands out due to the innovative design of the engine. And not only is the design innovative, it was very successful too. Between 1965 and 1983, almost 29’000 such engines were built!

Engine particulars:

20-cylinder V-engine
2’900 kW (3’950 hp) output
230 mm bore, 250 mm stroke
900 – 950 rpm nominal speed

Innovative engine design

In a nutshell: This engine is very compact, very powerful and it runs at a rather high speed for this size of engine: 900 – 950 rpm. This results in a rather remarkable maximum piston speed of just over 12 m/S at mid-stroke¹. Because of its high power and compact packaging, this engine has a high power to weight ratio. This is achieved through innovative design features that are worth looking at. Here we look at three of them.

1) 45 degree angle between A- and B-bank

V-engines are a common configuration for internal combustion engines. In a V-engine, the cylinders are arranged in two banks, which form a “V” shape when viewed from the front of the engine. The angle between these two banks is known as the “V-angle” and can vary significantly between different engines.

Most V-engines have a V-angle of 90 degrees. However, this engine type uses a V-angle of only 45 degrees. This design choice can have several implications for the engine’s performance and characteristics.

A 45-degree V-angle results in a more compact engine design compared to a 90-degree V-angle. This can be particularly beneficial in applications where space comes at a premium, such as in high-performance sports cars, in motorcycles or, you guessed it, in railway locomotives.

However, a smaller V-angle can also result in increased mechanical stress and vibration, as the forces generated by the pistons are not evenly distributed across the engine block. This can lead to increased wear and tear on the engine components, and may require additional mechanisms to counteract the imbalance.

In terms of performance, a 45-degree V-angle can potentially offer improved balance and smoother operation compared to a 90-degree V-angle. This is because the smaller angle allows for better primary balance and reduces vibrations.

In conclusion, while a 45-degree V-angle can offer some advantages in terms of compactness and potentially smoother operation, it also presents challenges in terms of increased mechanical stress and complexity of manufacture. As with any engineering decision, the choice between a 45-degree and 90-degree V-angle will depend on the specific requirements of the application.

2) Non-offset V-engine block

Some V-engine blocks have cylinders that are not offset (when viewed from above), meaning that the cylinders of both banks are exactly aligned. This design is known as a non-offset V-engine block. One advantage of this design is that it results in a more compact engine, as the cylinders are arranged in a more space-efficient manner.

However, there are also some disadvantages to this design. One potential issue is that it can result in increased mechanical stress and vibration, as the forces generated by the pistons are not evenly distributed across the engine block. This can lead to increased wear and tear on the engine components, and may require additional mechanisms to counteract the imbalance.

Overall, the choice between an offset and non-offset V-engine block will depend on the specific requirements of the application. While a non-offset design can offer some advantages in terms of compactness, it may also have some drawbacks in terms of increased mechanical stress and vibration. It is important for engineers to carefully consider these trade-offs when designing an engine.

3) “Blade and fork” connecting rods

The blade and fork type connecting rod arrangement is a unique way of joining two pistons to a single crankpin. In each pair of engine cylinders, a “fork” rod is divided into two parts at the big end and a “blade” rod is tapered from the opposing cylinder to fit this gap in the fork. This type of connecting rod has long found application on for example V-twin motorcycle engines (by BSA and Harley Davidson, among others) and V12 aircraft engines. The most famous example of a “blade and fork” engine is probably the Rolls Royce Merlin aircraft engine. Close to 200’000 such engines were built over many years. They were installed in many very famous aircrafts, such as the North American P51 Mustang, the Supermarine Spitfire, the Avro Lancaster and the Hawker Hurricane.

The advantage of this arrangement is that it allows both cylinders and rods to be in the same plane, as is required by an non-offset engine block. It also makes the motions of the two pistons identical. In the aircraft world, there were additional reasons for using fork-and-blade rods, rooted in history. Both Allison and Rolls-Royce produced V-12 engines which used knife-and-fork rods.

However, there are also some disadvantages to this arrangement. The underlying physics and manufacturing practice supporting plain journal bearings have improved to the point that big-end bearings no longer require the support of a full-width bearing. This means that side-by-side con-rods can now be used instead of fork-and-blade rods, which are more complex to manufacture.

Overall, the blade and fork type connecting rod arrangement has its advantages in terms of simplifying design and making piston motions identical, but it is more complex to manufacture than side-by-side con-rods. With advances in bearing technology, side-by-side con-rods have become a viable alternative. However, the choice between the two arrangements ultimately depends on the specific requirements of the engine design.

Work performed

The work that we carried out to get this 20-cylinder engine block back into good working condition consisted, broadly, of the following tasks:

Laser alignment and dimensional check
Hardness check and Magnetic Particle Inspection (MPI) to search for cracks
Line boring of the 12 main bearing pockets to remove existing fretting corrosion. We machined all main bearing bores to nominal dimension.
Blue fitting of the bearing caps

Metal Stitching and Line Boring on a Japanese Auxiliary Engine Block

17th May 2022

In late 2021, a Greek owner of a 4250 TEU container vessel approached us for the repair of an auxiliary engine. The 26-bore, japanese-made engine had suffered from a so-called “side kick” – the connecting rod had smashed a hole in the engine block, above cylinder #2.

As the vessel was about to call Singapore, QuantiServ Singapore arranged for one of its metal stitching specialists to go on board to conduct a comprehensive damage assessment.

As is nowadays almost always the case, our specialist deemed the engine block damage to be repairable. We engineered a repair proposal, consisting of metal stitching and in-situ machining to be carried out in our workshop in Singapore. The customer gladly accepted our repair proposal due to the obvious time and cost savings compared to replacing the engine block. He made arrangements for the 12-year old engine block to be sent to our Singapore workshop for repair.

The block arrived at our workshop in March 2022 and was immediately attended to. The repair work carried out included the following main steps:

We arranged for a tailor-made cast iron repair patch to be cast in a certified partner foundry. The repair patch was then stitched in place using Castmaster™ stitching pins and matching locks. This provides for a permanent, very strong repair.
As the damage extended into the lower cylinder liner bore, a repair sleeve was installed there. The repair sleeve guarantees a good fit with the cylinder liner o-rings, preventing water leaks.
The ovality of seven out of nine main bearing pockets was found to be excessive. This finding was independent of the accident but needed attention too. We corrected the ovality with in-situ line boring.
All eight cylinder liner landing surfaces in the engine block were machined to clear them from corrosion and cavitation damage.

A Magnetic Particle Inspection (MPI) was carried out on the completed repair to the satisfaction of the customer and attending class surveyor.

From start to finish, the repair work took approximately four weeks to complete, well in time for the engine block to be sent back to the vessel during her next routine call to Singapore.

Engine block damage at cylinder number 2 — Damaged engine block

Machining of the cylinder liner landing surface

Cylinder liner landing surface after machining

Another job well done — After completion. Another repair job well done!

More metal stitching information

Two-stroke Bedplate Line Boring in Mexico

5th March 2018

When a six year old bulk carrier suffered main bearing failures on its Japanese-made main engine, QuantiServ was called in for an initial inspection and for discussions on how to arrange the repair in the fastest and most economical way. The inspection in Veracruz, Mexico, showed that main bearings # 7 and 8 failed and that the crankshaft as well as the main bearing pockets were damaged.

The crankshaft was beyond repair and had to be replaced by a new one. The bed plate, on the other hand, could be recovered by line boring. With the engine frame lifted up, QuantiServ’s in-situ specialists carried out

a thorough inspection of the bedplate, including NDT crack detection and hardness measurements
laser alignment checks before line boring
line boring of main bearing pockets # 7 and 8
laser alignment checks after line boring
blueing checks

The work was carried out successfully while the vessel was alongside in the shipyard in Mexico.

: Setting up the boring bar

: Line boring

: Flatness measurement

: Flatness measurement

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