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.

 

Upcopming Webinar: Repairing the Irreparable

Advanced in-situ machining and metal-stitching repair solutions

 

In the marine sector, every time a machinery component is worn out or damaged, an important decision needs to be made: To either repair or replace the component with a new one.

Factors such as technical or operating possibilities, lead time for a replacement component, size or weight of the damaged component, the downtime required for the replacement works, loss of revenue, cost of the repairs etc need to be carefully evaluated before deciding to repair or replace a key component with a new one.

Join QuantiServ and Wärtsilä on the 7th of July 2021 at 14:00SGT to explore:

  • Possibilities and benefits of repairing a damaged machinery component with advanced in-situ machining, instead of replacing it.
  • Possibilities and benefits of repairing a damaged machinery component with metal stitching, instead of replacing it.
  • Reference cases

Naeem Arshad Zubair

Sales Development Manager, Specialized Services, Wärtsilä

Moderator

Peter Schwiecker

Technical Manager,
QuantiServ

Presenter

Jeff Reed

Sales Manager,
Lock-N-Stitch, QuantiServ

Presenter

Key Data 2020 – Number of Customers and Orders Increased

We have steadily grown our reach and our customer base during recent years. In 2020, our 356 staff have successfully processed close to 3’000 Reconditioning, In-situ Machining, Metal Stitching, Epoxy Resin or Mobile Team orders from nearly 700 individual customers.

We carried out 70% of these orders in one of our 14 workshops. The remaining 30% of orders we processed on board ships or in customers’ plants.

The customers that we served stem from a wide range of industries. On average, we commenced a new in-situ machining assignment every three hours, anywhere in the world.

Key Data 2020:

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.

Four-stroke Engine Block Metal Stitching and Crankshaft Machining

Over the years, medium-speed diesel engines have become very popular for a variety of applications, most notably in ship propulsion and in power generation. Accordingly, the number of such engines in service is very large.

Due to their large number and to the relatively high nominal speeds, combined with significant mass inertias, one would from a theoretical stand point expect more fequent and more severe damages on medium-speed, four-stroke diesel engines than on low-speed, two-stroke ones. That this is indeed the case in practice is evidenced be the fact that we are frequently contacted and subsequently repair a few dozen cases of severe engine damage every year.

Here is a typical example, one of many:

A Korean-made auxilliary engine with eight cylinders, 210 mm bore and 320 mm stroke suffered a serious bearing failure on crankpin #1. The engine block and crankshaft both got severely damaged, due to the connecting rod impacting both. The accident happened while the vessel, a Ro-Ro ship, was trading in East Africa.

Her next port of call was in Florida, United States, where our technicians went on board for a thorough inspection. They determined that both the crankshaft and engine block were repairable. As in addition to crankpin #1, which was badly damaged, all other pins were found with corrosion and scratch marks, we suggeted to the customer to offload the engine and to sail a few weeks without it. The customer agreed.

The engine was offloaded in Freeport, Texas, for repair and was delivered back to the vessel 46 days later in the same port. In the meantime, the vessel continued to sail with one engine less. The duration of the voyage, 46 days, was more than sufficient for our specialists to repair the crankshaft and engine block according to our very exacting standards.

Repair of the crankshaft

Due to the damage sustained by the accident, crankpin #1 had to be machined to – 3.00 mm. This was necessary to clear all dent marks. And as the other seven crankpins were suffering from scratches and/or corrosion, it was decided to machine them all to – 0.50 mm.

Repair of the engine block

Repair of engine block before and after

The cavity in the block caused by the accident was fairly substantial. A total volume of about 6’000 cm³ (366 in³) of material was missing and cast iron plates with a thickness of 19 – 51 mm (0.75 – 2 in) had to be repaired.

Our cast iron repair specialists scanned the damage with a 3D scanner. The data thus acquired was then used to fabricate a perfectly-fitting cast iron repair patch. The repair patch was stitched in place with stitching components, chiefly Castmaster stitching pins and locks, that are sold by Lock-N-Stitch.

After the repair was completed, it was hardly visible and the customer was very pleased with the outcome.

Here is a step-by-step description of how the block repair work was carried out:

 

Jaw Crusher In-situ Machining, 700 Meters Underground

In November 2018, our in-situ specialists carried out machining work in one of the world’s most modern underground mines, located in central Sweden. The mine processes about 2.5 million tones of ore annually and produces gold, silver, zinc and lead.

The assignment lasted about a week and consisted of milling, drilling and tapping work on a large jaw crusher located at a depth of 700 meters. There, the ore is crushed before it is hoisted to the surface for further processing.

Our specialists machined the upper section of both the stationary and the moving jaw. On each jaw, they milled off about 26,000 cm3 of steel and then drilled and tapped them so that a newly fabricated section could be bolted on.

Our Brand-new Case Study Page is now Online!

The new QuantiServ Case Study page is now online. It introduces recent work that we have done for customers coming from a variety of industries ranging from Marine, Mining, Hydro and Thermal Power Plants to Oil & Gas.

The cases are sortable by industry and cover services such as in-situ machining, metal stitching, reconditioning and many more. They each include a short description of the problem that the customer was facing, the solution and include many before/after and in-process pictures.

Case Studies

 

QuantiServ’s In-situ Machining Specialists are Very Highly Trained

The last few weeks have been a busy period for our internal trainers at our in-situ training center in Gothenburg, Sweden. Courses were scheduled back to back. In-situ machining colleagues from around the world were undergoing refresher training on a variety of topics: in-situ crankpin machining, in-situ heat treatment (annealing), engine block machining, etc.

At QuantiServ, we very highly value formal training. All our in-situ machining specialists undergo rigorous training and assessment when they first start to work for us. And it does not stop there. As we constantly keep on further developing and improving our tools and processes, we regularly call the in-situ machining specialists that normally are stationed all around the world back to our in-situ training centre in Sweden to equip them with the most updated skills and knowledge.

This was the case with colleagues from Italy and Brazil that joined a training course last month. Even though some of them already work for us for ten years or more, there are always new tricks that they can pick up. A lot of knowledge sharing and networking takes place during these courses too. The trainees meet with our designers and tool developers and provide them with valuable feed-back and experience from the field. This information then flows into the next generation of tools so they become ever better and more efficient. It is highly trained machinists and cutting edge tools that keep QuantiServ at the forefront of the in-situ machining industry.

Crankpin machining training

Crankpin machining training

Crankpin machining training

Crankpin machining training

 

 

 

 

 

 

 

 

In-situ heat treatment training

In-situ heat treatment training

In-situ machining specialists from Italy

In-situ machining specialists from Italy

 

 

 

 

 

 

 

 

Our Brazilian colleagues proudly showing off their renewed certification. Notice the quality of the pin surface.

Our Brazilian colleagues proudly showing off their renewed certification. Notice the quality of the pin surface.

 

 

 

 

 

 

Brand New Light Surface Grinding Tools Now Available for Sale!

We are asked frequently, whether we are selling the in-situ machining tools that we have developed and manufactured and that our specialists use in the field. While such requests are of course flattering and while we appreciate that other companies find our tools appealing and would like to purchase them, we have up to today always politely declined such request. The reason is that we first and foremost see ourselves as a top-notch in-situ machining company and not as a tool manufacturer. Our tools are thus a means to end – the more accurate and efficient they are, the better the result of our machining assignment that our customer comes to enjoy.

Our very newest Light Surface Grinding machine (LSG) has now proven to be so popular, that we have decided to break with tradition and to make it available for sale.

The machine was designed to be as compact and portable as possible. It has an adjustable base, no heavy adapter plates are therefore necessary. Its total weight is 30 kg (66 lbs). This is significantly less than any comparable machine currently on the market and means that it does not have to be sent as cargo to a ship or power plant, but can be brought along as checked-in luggage.

The tool’s main purpose is to quickly and accurately skim the cylinder liner landing surfaces at the top of medium-speed engine blocks. It can be used to machine diameters of 360 – 670 mm, which makes it suitable for engines with a bore size of 260 – 500 mm. Additional accessories to also skim the landing surface on the cylinder liner are also available.

The advantages of the Light Surface Grinder (LSG) are many:

  • High accuracy
  • Fast to set up and easy to use
  • Compact design
  • No adapter plates are necessary as the machine’s base is continuously adjustable
  • A single machine covers the range from ⌀ 360 – 670 mm
  • Total weight = 30 kg (66 lbs)

Contact us for more information, or to order one.

Contact us

 

 

In-situ Straightening (Peening) of a Bent Crankshaft

The pictures below show the straightening and subsequent machining of a bent crankshaft, carried out by our specialists in Singapore. All work was carried out in-situ. The crankshaft was found bent following a crankpin bearing failure.

The crankshaft belongs to a 12-cylinder, 40-bore engine installed on a dredger. A straightness check revealed that its run-out was 0.18 mm, which is far beyond the acceptable threshold.

Our specialists therefore carried out in-situ straightening by peening the shaft. Peening is a cold-process that consists of applying a small force repeatedly to the correct places to bring the shaft back to its original straightness. This took one day and resulted in an improvement of the run-out from 0.18 mm to 0.03 mm.

After straightening, our specialists machined the crankpin to -7.00 under-size and then polished it.

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.

Be Aware of Cam Effect/Ridge Wear that Affects Four-Stroke Crankshafts!

Whenever a four-stroke engine has accumulated around 60,000 running hours or more, then its crank pins are in all likelihood affected by what is called the “cam effect” or “ridge wear”.

This phenomenon develops over time and manifests itself in an uneven wear pattern that is, with the right tools, easily detectable as a protruding band (“cam”) that goes around the circumference of the crank pin. It usually only develops on engines equipped with grooved bearing shells and its development is a function of time. The more impurities (abrasive particles) the lubricating oil contains, the faster the cam effect develops.

The two major makers of medium-speed diesel engines, MAN Diesel & Turbo and Wärtsilä, have booth issued Service Letters to make their customers aware.

The following pictures are typical and exemplify well how the cam effect develops and what damage it can cause. The pictures were taken during an attendance on a German-owned small tanker, where QuantiServ’s specialists machined one crank pin and polished all the others on the vessel’s single 50/54 main engine. The damage was in fact so severe that in-situ heat treatment (annealing) had to be performed too in order to reduce the crankpin’s hardness, which had increased as a result of the failure.

QuantiServ very much recommends to all owners and operators of medium-speed four-stroke engines to keep a close eye on the condition of the crankpins and to regularly inspect them once they have surpassed around 60,000 running hours. The cost of rectifying the pin geometry in good time pales in comparison to the cost of a repairing a failed crankpin bearing. And fail they will, if no action is taken.

Read more

 

 

Reconditioning of Fourteen 96-bore Cylinder Covers

In November 2017, our Reconditioning Centre in Shanghai carried out reconditioning of fourteen cylinder covers for a major European ship owner. These covers came from one of the world’s largest container ships, equipped with a 14-cylinder, 96-bore main engine.

All fourteen cylinder covers and all fourteen exhaust valves were reconditioned within a period of less than one month, while the vessel was undergoing steel work at a shipyard in Qingdao.

This was the third vessel out of a series of similar vessels for the same customer. QuantiServ carried out the reconditioning work for all these vessels.

Significant Reconditioning and Field Service Job in Shanghai

In September our Reconditioning Centre in Shanghai carried out a a major reconditioning and field service order for an Iranian-owned tanker that was docked in a Chinese shipyard. This example shoes well the breadth of QuantiServ’s offering.

The following components were reconditioned:

  • 8 piston rods
  • 7 piston crowns
  • 7 cylinder covers
  • 6 exhaust valves
  • 7 crosshead pins
  • plus a number of smaller, related components

We also sourced for the customer a couple of new crosshead and crankpin bearings while we re-babbitted others, such as for example guide shoes.

QuantiServ engineers also carried out the overhaul work on board, supervised the oil flushing and attended the seatrial after the docking. We also replaced the stern tube shaft seals and in-situ polished some of the crankpin journals.

All the work was completed in 32 days.

Polishing All Main Journals and Crankpins on World’s Largest Engine

QuantiServ in-situ machining specialists from China, Sweden and Singapore joined forces in a shipyard in China to carry out in-situ polishing on one one of the world’s very largest diesel engines. The 14-cylinder, 96-bore engine is installed on a 14,000 TEU container ship.

Our engineers and technicians worked in two shifts, around the clock, seven days a week to machine-polish 17 main journals and 14 crank pins while the vessel was docked in Beihai Shipyard, Qingdao, undergoing steel work. It was one of the most extensive polishing jobs that we have ever carried out. And it was done in record time!

All the necessary dismantling and reassembling work was carried out by us as well. In a case like this it pays off that many of our in-situ personnel are multi-skilled – they don’t only do the machining work, but can conduct any mechanical work as well if required.

In addition, our reconditioning centre in Shanghai also carried out cylinder cover reconditioning for a sister ship, belonging to the same customer, that was docked in the same shipyard a few weeks earlier.

It’s All in a Month’s Work for QuantiServ’s In-situ Machining Crew!

On board various ships and oil rigs, in power plants and in factories: Far from being idle during the holiday season, during the month of July our in-situ specialists were maintaining and repairing our customers’ equipment in 26 different countries, across four continents. No other in-situ machining company has such global reach and completes more projects than QuantiServ. Wherever the location, whatever the damage – it’s all in a month’s work for us!

Explore the interactive map below and discover what services our in-situ engineers have been providing to our customers during the month of July 2017.

QuantiServ at the Norshipping 2017 Exhibition in Oslo

Our participation at the recently held Norshipping 2017 exhibition in Oslo, Norway, was very successful. We displayed our exciting metal stitching, in-situ machining and reconditioning solutions. These solutions created quite a lot of customer interest and led to many interesting discussions. It was also nice to meet many existing customers again and to know some new ones too.

Our next stop will be the Philmarine 2017 exhibition, which will be held from 12 – 14 July 2017 at the SMX Convention Center in Manila. We will be at booth 111/118. Come and visit us there.

QuantiServ at the Sea Asia 2017 Exhibition in Singapore

Sea Asia Exhibition 4Our participation at the recently held Sea Asia 2017 in Singapore was a big success. We displayed our metal stitching and in-situ machining solutions, as well as the refurbishment of four-stroke cylinder covers by furnace brazing, which we are particularly proud of. These solutions created quite a lot of customer interest and led to many interesting discussions.

Our next stop will be the Norshipping Exhibition in Oslo, 30 May – 02 June 2017, where we will be at booth D 05-34. Come and visit us there.

Crank pin machining mock-up

Crank pin in-situ machining mock-up

Furnace brazed 32-bore 4-stroke cylinder cover

Furnace brazed 32-bore 4-stroke cylinder cover

Fully reconditioned 35-bore 2-stroke cylinder cover

Fully reconditioned 35-bore 2-stroke cylinder cover

Flywheel Teeth Dentistry on a Container Ship in Hong Kong

 

Our in-situ specialists from QuantiServ Dubai have just completed another flywheel repair. This time it was for a very large European owner, on one of their large container ships with a 12-cylinder, 96-bore engine while on anchorage in Hong Kong. Our specialists machined off two damaged teeth and installed an insert, which they had pre-fabricated at their workshop before boarding the vessel and which they sent on board jointly with the in-situ tools.
The total work took 42 hours – three long days of work – and the result is something that they can be very proud of!

Damaged flywheel with two severely damaged teeth

Damaged flywheel with two severely damaged teeth

Removal of the damaged teeth by in-situ milling

Removal of the damaged teeth by in-situ milling

Pre-fabricated insert installed, repair completed

Pre-fabricated insert installed, repair completed

ABC Engineering Pte. Ltd. in Singapore joins QuantiServ

abc-logoWe are very honoured and happy to announce that all personnel from ABC Engineering Pte. Ltd. have decided to join QuantiServ with effect from 1 April 2017. This combination of forces further extends QuantiServ’s offering and geographical reach, particularly in Indonesia.

ABC Engineering is a well known company with excellent reputation that has been providing in-situ crankshaft and engine block repair services to customers in Southeast Asia since the 1970s.

The personnel from ABC Engineering and QuantiServ look forward to continue to serve ABC Engineering’s customers as reliably and to the same exacting standards as they always have.

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.

QuantiServ unveils its brand new, centreless facing machine

Months of design and development work came to culmination last week at a dry dock in Marseille, France, when QuantiServ’s new, state-of-of-the art surface facing machine was deployed into the field for the very first time. The machine is designed for in-situ milling and grinding of large, circular surfaces such as those found on large thrusters and well inserts, on slewing rings, hydro turbines, and on blast furnaces. Its first assignment was on the steerable thrusters and well inserts of a cruise ship.

The machine is highly versatile and able to machine surfaces that are vertical, horizontal or inverted. It is ideal to machine circular surfaces between 1500 mm and 5000 mm diameter.

The main advantage of this machine is that it is centreless. The machining head is supported very near to the surface that is to be machined. Thus, the cantilever-effect, which always occurs on traditional facing machines with a central pivot system and that negatively impacts their accuracy, is completely eliminated.

Surfaces that are not circular but rectangular or square shaped, are better suited to X-Y milling and grinding, which QuantiServ also offers.

Getting the machine ready for action at the bottom of the drydock

Getting the machine ready for action at the bottom of the drydock

Metal stitching test piece resists water pressure of 12 bars

Metal stitching test piece resists water pressure of 12 bars

Metal stitching, as long as it is carefully and properly carried out by trained technicians, is tight against gases and liquids. To demonstrate this, QuantiServ has manufactured two cast iron half-shells and has joined them together by metal stitching. The resulting container was successfully pressurized to 12 bars (175 psi) and no leak was observed.

This proves that there is no issue to repair cooling water spaces in for example engine blocks, where the cooling water pressure typically lies around 3 – 4 bars (44 – 58 psi), by metal stitching. In fact we knew this well, because we have done it successfully many times. But that the stitching could easily withstand 12 bars impressed even us.

 

 

Rudder stem housing In-situ Machining on new type of LNG carrier

laser-alignment-rudder-stem

Laser alignment of the rudder stem housing

Rudder stem housing in-situ machining on a new type of LNG carrier

QuantiServ have a long-term and good cooperation with many newbuilding and repair shipyards.

Recently QuantiServ were requested to carry out in-situ machining (line boring) of a rudder stem housing on a new type of LNG carrier that is under construction in a Chinese shipyard. Our team were on-board to calibrate the inner diameter of the rudder stem housing and found that the ovality and parallelism were out of limit.

Thereafter, a laser alignment check of the rudder stem housing was done and the corrections to be made were calculated. Finally in-situ line boring of the rudder stem housing was carried out successfully.

In-situ line boring of rudder stem housing

In-situ line boring of the rudder stem housing

A final check showed that the ovality, parallelism, roughness and centre line of the rudder stem housing were all within tolerance. The shipyard was very satisfied with our service and confirmed the final result.