Line Boring of a Locomotive’s Diesel Engine Block

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
Line boring of the main bearing pockets
Line boring of the main bearing pockets

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

Read more about line boring

1This is an approximation calculated according to the formula PSmax = 250 x π x 950, where 250 is the piston stroke in millimeters and 950 is the engine speed in revolutions per minute

20-cylinder engine block at workshop
The 20-cylinder, welded engine block in our workshop. Note that the gear train is centrally located.
The block turned on its side with main bearing caps removed.
The block turned on its side, main bearing caps removed
Blueing test of the main bearing cap serration
Blueing test of the main bearing cap serration

Metal Stitching Repair on a Small Diesel Engine Bed Plate

A customer reached out to us in May 2022 in Singapore, asking for our help in repairing a damaged two-stroke engine bed plate. The cast iron bed plate suffered from cracks and missing material, inflicted as consequential damage following a connecting rod failure.

Our experts immediately carried out an inspection on board. They found this main engine bed plate to be repairable, but determined that the damage area could not be accessed properly without removing the engine’s A-frame. The shipowner therefore decided to bring the 19-year old, 100 m long asphalt carrier alongside a ship repair yard in Singapore.

“We are very satisfied with your service.”

Customer’s Technical Superintendent, by email, August 2022

Damage location
Damage location

While the shipyard’s personnel dismantled the ø 38 cm bore, japanese-made engine, our specialists prepared a repair plan and discussed it with the customer and classification society. Simultaneously, they arranged for a tailor-made repair patch to be made, including a set of accompanying classification certificates.

In late June 2022, once the engine had been suitable dismantled, three metal stitching specialists from QuantiServ Singapore carried out the bed plate repair. They first removed all damaged and deformed material and dressed up the facture. They then installed the newly fabricated cast iron repair patch with Castmaster™ stitching pins. They repaired all cracks in the same manner, including a 150 mm long one that had not been visible until the deformed material had been removed.

Once all stitching pins had been installed, our specialists then added high-strength locks, made of heat treated steel. These are always installed perpendicular to the fracture line and serve to distribute stresses over a wider area. They also add additional strength to the repair.

The completed repair was thoroughly checked by Magnetic Particle Inspection (MPI). The attending classification surveyor witnessed this. And last but not least, our in-situ team carried out a laser alignment check of the main bearing pockets. This was done to rule out any deformation in the bedplate due to the impact forces exerted upon it by the broken connecting rod.

Damaged bed plate prior to repair
Damaged bed plate prior to repair
Damage area prepared for stitching repairs
Damage area prepared for stitching repairs
Classification surveyor attending the Magnetic Particle Inspection (MPI)
Class surveyor witnessing Magnetic Particle Inspection
Installation of stitching pins along the crack line
Installation of stitching pins along the crack line
Stitching in the repair patch
Stitching in the repair patch
Magnetic Particle Inspection (MPI) of the completed repair
Magnetic Particle Inspection (MPI) of the completed repair
Magnetic Particle Inspection (MPI) of the completed repair
Magnetic Particle Inspection (MPI) of the completed repair
Preparing the repaired bed plate for laser alignment check of the main bearing pockets
Preparing the repaired bed plate for laser alignment check of the main bearing pockets

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

Line Boring Work on Large Hydraulic Forming Press

Last month, our colleagues from QuantiServ Shanghai completed an in-situ repair assignment on two large hydraulic forming presses. The two presses, that have a capacity of 2,000 tons each, are installed in a factory in Northern China. They are used to manufacture automobile chassis parts for BMW and Mercedes Benz, among others.

The situation on both presses was almost identical. Specifically, it was the gearbox sections at the upper ends of the press that were in need of repair. A total of six bearing housings (2 x 3 each) were found to be worn. Their diameters, concentricity and coaxiality were all out of tolerance.

Large hydraulic forming press
One of the two 2,000 ton hydraulic forming presses that we worked on

To bring the bearing housings back into specification, our in-situ specialists line bored them. Thereafter, they installed specially manufactured bushes. Non-destructive crack testing and multiple laser alignment checks prior, during and after the repair completed the work.

To minimize expensive down-time, the work was carried out around the clock, 24/7, to the full satisfaction of the customer.

Installing the boring bar
Installing the boring bar
Laser alignment check in progress
Laser alignment check in progress
During line boring
During line boring
Coaxiality calculation
Coaxiality calculation

Stern Tube Machining: Two Case Studies and a Time-Lapse Video

Within the marine industry, in-situ machining of stern tube bearing pockets or of bearings themselves belong to a group of line-boring assignments that we carry out very frequently. In this post we would like to introduce two recent cases, one performed in Las Palmas, Canary Islands, and the other in Singapore.

Case 1: Machining of stern tube forward and after bearing pockets in Singapore

Damage to the stern tube bearings is found during the routine dry docking of a vessel in a shipyard in Singapore. Upon this discovery, the ship owner turns to us for advice. As this is evidently an unplanned and serious case, our specialists mobilize very quickly and carry out an initial laser check of the pockets’ alignments and geometries. The check reveals that the bearing pockets are misaligned and that the ovality that is measured is excessive.

The customer concurs that line boring presents itself as the best remedy. Again, our machining specialists mobilize quickly and rectify the poor alingment and ovality. Both the forward and after bearing pockets are machined. Working around this clock, this is acomplished in just five days.

We arrange two new bearings to be made in Spain on an urgent basis. Once they are delivered, we supervise their installation at the shipyard in Singapore. A final laser alignment check confirms that the alignment is correct now. We also carry out a load test of the entire shaft line and attend the sea trial, which goes smoothly.

Case 2: Machining of stern tube after bearing pocket in Las Palmas, Canary Island

A Norwegian ship owner decides to upgrade the stern tube bearings and seal assembly on a 20-year old ship to a newer, improved design. The upgrade means that the after bearing pockets has to be machined to accomodate the new bearing bush and seals.

Our work scope is as follows:

  • Measure stern tube diameter using a micrometer
  • Find the existing center line through laser measurement
  • Set up the CLB80 line boring machine inside the stern tube and align it with the help of lasers
  • Machine the stern tube according to drawings
  • Final measurement of the stern tube using a micrometer and laser measurement equipment

As is usually the case with stern tube bearing bushes, three different inner diameters (Ø525, Ø524 and Ø523 mm) have to be machined. The  total lenght of the of the stepped area is 935 mm. Two QuantiServ specialists from Gothenburg, Sweden, complete the work in two weeks.

They use our new CLB80 line boring machine that we designed and built ourselves. This machine is capable to very accurately bore holes with Ø140 – 600 mm that are up to 10,000 mm long. Its flange facing capability ranges from Ø90 – 700 mm.

Here is a time-lapse video of the line boring work performed in Las Palmas. The laser alignment and measurement works taking place before and after the line boring are omitted from the video to keep it short.

 

Two-stroke Bedplate Line Boring in Mexico

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.

Lateral surfaces before and after in-situ machining

In-situ machining of lateral surfaces on 20V32 engine block in Bangladesh

Lateral surfaces before and after in-situ machining

Lateral surfaces before and after in-situ machining

In-situ machining of lateral surfaces on a 20V32 engine block in a power plant in Bangladesh

In October 2016, QuantiServ received an urgent request to carry out in-situ machining on a 20-cylinder 32-bore engine block in a power plant in Bangladesh. During the replacement of the crankshaft it was noticed that both lateral surfaces of main bearing cap number 5 showed signs of severe fretting and were in need of machining.

Immediately, in-situ machining equipment was prepared at QuantiServ’s Dubai workshop and was sent to site. Once the equipment had arrived at site, QuantiServ’s engineers from Dubai performed in-situ machining on the engine block to achieve a clean surface that was free from damage. The in-situ machining process was constantly monitored by laser to ensure perfect alignment and adherence to very tight machining tolerances.

The main bearing cap was sent to a local workshop in Bangladesh for machining and installation of compensation plates. This process was supervised by QuantiServ’s engineers. Once the machining was completed, all mating surfaces for the main bearing cap were checked with marker blue to ensure a perfect fit.

Once the work was completed, a final check by laser on the assembled bearing cap showed that both the bore alignment and diameter fully conformed to the engine maker’s specification.