USA Archives - QuantiServ

Thread Repair on the Low-Speed Rotor of a Wind Turbine

17th November 2023

A work site with a view

It is not a secret anymore that our thread repair solutions excel in the most demanding applications and environments. It is therefore not surprising that our colleagues from Lock-N-Stitch were recently contacted for assistance in repairing damaged threads in the hub of a wind turbine operating in the American Mid-West. Our specialists quickly engineered a repair solution and brought it to life inside the 4.2 MW turbine’s nacelle, which sits 105 meters (345 feet) above ground.

Three out of 88 bolt holes that connect the rotor hub to the (low speed) rotor shaft had their threads stripped. Our solution was to machine these to over-size and to install Full-Torque^TM thread inserts. Unlike convential thread repair inserts, Full-Torque^TM thread inserts are equipped with the patented spiral-hook thread, which makes them the ideal for any application, where superior strength is required.

The three inserts that the Lock-N-Stitch specialists installed have an M48 x 5 internal thread that is 130 mm deep. They are also counter-sunk to a depth of 25 mm.

Inside view of the nacelle, towards the rotor, with the drive train components (gear box, generator, ...) removed.

Our specialists locked the inserts in place with three bolts, to prevent them from ever rotating during any future loosening of the bolts.

A few days after we completed our work and after the drive train had been installed back, the customer reported that the alignment of our inserts had been found to be perfect.

Crack Repair on an Excavator Counter Weight

10th June 2023

To prevent them from toppling over during digging, transporting earth and raising or lowering the bucket, excavators need to be fitted with a counter weight at their back that balances out the forces.

Typically, these counter weights are made of cast iron. Cast iron offers a number of advantages over other materials, such as concrete: Higher density, less fragile than concrete, made by casting so that even complicated shapes are easy to produce.

Even though cast iron is a strong and very long-lasting material, high degrees of wear and tear common in the construction industry do take their toll over time.

A large provider or construction rental equipment contacted QuantiServ about repairing a cracked counter weight on a relatively large, USA-made excavator.

An inspection showed the presence of three individual cracks with a combined length of 750 mm. Why the counter weight was suffering from cracks is not entirely clear. One or more collisions with an object during tail swing, or latent stresses in the casting might be possible explanations.

It was in any case apparent, that unsuccessful attempts had been made to repair two of the cracks by arc welding. It is very hard to weld cast iron. Most attempts fail, especially if the repair is attempted under site working conditions.

At QuantiServ we always repair cast iron by metal stitching, which is a cold process and which results in a repair that is always as strong as the original part, and often stronger.

The failed welding meant that we had to spend more time and effort during the metal stitching than would normally be required. We estimate that it took about twenty additional working hours to deal with the damage caused by the arc welding.

We charged the customer a total of USD 15’000 for the repair, including traveling and accommodation costs. The retail sales price of a new counter weight was USD 36’850, meaning that the customer’s insurance company saved USD 21’850 by having it repaired rather than replaced.

Metal Stitching an Engine Block from 1921 in-situ!

26th November 2022

1921 Duesenberg Model A

We do a lot of in-situ work. We routinely carry out machining and metal stitching work, among others, on components that are too large to be moved to a workshop or where dismantling work is too time consuming or costly. But repairing a an antique car engine block, in the chassis, in a museum, is still quite special. Even for us.

The engine in question is an in-line, eight cylinder one with a bore of 72 mm and a stroke of 125 mm (2.875″ x 5″). With a swept volume of 4’256 cc, or 260 cubic inches, this early Duesenberg Model A engine is capable of producing up to 88 hp (66 kW) of power.

Repair in progress. The engine remained in the chassis, only the cylinder head was removed.

We got the opportunity to work on this engine as cracks had began to show at the corners of the engine block. The cracks originated from the threaded bores housing the cylinder head studs. They extended towards the outside of the engine block on one side and into the cooling water passage on the other.

The fact that the engine was left inside the chassis made the repair a little more challenging than usual. Our metal stitching expert had to use a mirror for much of the repair work. Without it he could not see, let alone repair the cracks at the rear end of the engine block. In addition to sealing the cracks with stitching pins, our expert also installed Full Torque™ thread inserts at the threaded bores. Unlike conventional thread repair inserts, Full Torque™ inserts do not create spreading forces. They are therefore the perfect solution for cases like this one, where threaded bores close to an edge have to be repaired.

Cracks extending from the cylinder head stud bores to the outside and to the cooling water space

Installation of Castmaster stitching pins. They are the strongest and most advanced stitching pins on the market today.

Ultrasonic inspection of the casting to determine the wall thickness

Metal stitching in progress. Due to the location of the crack a mirror was used.

The completed repair. Cracks stitched and Full Torque thread inserts installed.

Links

Metal Stitching

Metal stitching is a very well-established repair method. It is applicable to a wide variety of materials such as cast iron, cast steel and many non-ferrous metals.

Thread Repair

The repair inserts that we use to repair damaged threads are super strong and do not create spreading forces. They are ideal for high-load applications.

Metal Stitching a Fractured Engine Block from 1913

25th November 2022

Pierce Arrow

This post describes the repair of a Pierce Arrow engine block from 1913. The Pierce Arrow was the largest production automotive engine at its time. The swept volume of this 6-cylinder, 48 hp (36 kW), engine amounts to a whopping 13’500 cc (824 cu in)!

This engine is of the T-head engine type, which is essentially an early form of crossflow engine. This design is characterized by two separate camshafts, one on either side of the cylinder. One camshaft operates the inlet valves and the other the exhaust valves. This makes this engine design quite complex and expensive to produce.

The main advantage of the T-head engine design is the fact that it is not at all prone to knocking – a condition where the gasoline vapour in the cylinder ignites too early by itself due to compression, before it is lit by the spark plug. Knocking was a big issue especially during the early decades of the 20th century, when gasoline sold typically had a very low Octane rating. T-head engines were therefore popular until about 1920, when better fuel became widely available. At that time, the disadvantages of the design started to outweigh the advantages.

A large piece had broken off the cast iron engine block and had to be reattached

The in-line 6-cylinder Pierce Arrow cast iron engine block that we received for repair at our workshop at Lock-N-Stitch in California, USA, was severely damaged. A large piece of the casting had been broken off at the block’s front (timing belt) end.

Our metal stitching specialists successfully reattached it. In order to do so, they installed about thirty Castmaster™ stitching pins over a total fracture length of 160 mm, in material with a thickness ranging from 12 – 16 mm. For additional strength, they also installed two high-strength locks perpendicular to the fracture line.

The fracture line passed through a hole for a positioning dowel pin. To repair that, our specialists first closed the hole by installing a solid Full Torque™ plug, before drilling it anew in the exact location.

Repair completed. Stitching pins, locks and Full Torque insert installed

Repairing a V12 Flathead Engine Block from 1934

2nd November 2022

Packard Twelve

We routinely work on museum pieces. In this post we introduce a typical case: The repair of a Packard Twelve engine block from 1934, carried out by our colleagues from Lock-N-Stitch in California.

As the name implies, the Packard Twelve is a 12-cylinder engine. It is a flathead engine, sometimes also called side-valve engine, where the intake and exhaust valves are contained within the engine block rather than within the cylinder heads. Flathead engines were very popular until the 1950s and were built in large numbers by automotive manufacturers. Their advantage is their simplicity, compactness, reliability and low cost as the flathead design obviates a complicated valve train. Such engines therefore need far less components than alternative designs such as, for example, single or double overhead camshaft arrangements.

The main disadvantage of the flathead engine is its relatively low efficiency and power output. The Packard Twelve V12 engine has a displacement of 7300 cc (445 cu in) and a maximum output of 119 kW (160 hp).

Engine block received with cracks in both longitudinal side walls and around the valve seats

Repair of cracks in the side walls of the engine block

When the engine block was delivered to us, it contained eleven cracks of various lengths. Some were small, others rather long. Added together, they amounted to a total length of 200 mm. In addition, the block suffered from corrosion and material loss around the camshaft spaces.

The cast iron block had been “repaired” before by arc welding. This has not been a great success – new, fairly large cracks could be seen extending to the left and right of the weld.

As they always so on cast iron parts on which someone has already been attempting a repair by welding, our specialists cut out all material in the vicinity of the weld, in the so-called heat affected zone. This is our standard operating procedure. Whenever cast iron is welded at, the heat from welding burns out the carbon, which constitutes between 2% and 4% of the cast iron. Once the carbon is burnt, the cast iron becomes hard and brittle, looses its structural integrity and becomes worthless.

To replace the cut out material on both longitudinal sides of the block, our specialists installed repair patches made of cast iron. They stitched them firmly in place with Castmaster™ stitching pins. Similar pins of various lengths and diameters were also used to repair the cracks found in various locations on the block, in material ranging from 3 – 10 mm thick. Some of these cracks are visible in the pictures below.

Our specialists also installed five Full Torque™ thread inserts to repair thread holes damaged by corrosion and erosion.

The engine block had been arc welded in the past. As expected, this did not solve the problem but led to further cracks extending left and right. — The engine block has been arc welded in the past. As expected, this did not solve the problem but led to further cracks extending to the left and right of the weld.

Crack extending leftward from the weld, serious corrosion at the edge of the sealing surface.

We removed the material that has previously been welded and installed a repair patch.

Crack extending rightward from the weld. Again, serious corrosion at the sealing surface. — Crack extending rightward from the weld. Again, serious corrosion at the camshaft cover sealing surface.

Installation of stitching pins to seal the crack

Skimming of cylinder head landing surfaces

Repair of cracks around the valve pockets

A thorough magnetic particle inspection (MPI) of the block revealed hairline cracks between some of the valve seat and cylinder liner bores. We permanently repaired these cracks by installing small size stitching pins.

After completion of the repair, we took the opportunity to skim all cylinder head gasket mating surfaces, on the engine block as well as on the two cylinder heads.

Crack between valve seat and cylinder bore clearly visible during Magnetic Particle Inspection (MPI)

Cracks between valve seat and cylinder bores successfully repaired

Another crack, seen here under Ultraviolet (UV) light during MPI

Tractor Engine: Stitching Repair in the Combustion Chamber

6th October 2022

Ford 1710

This post is about a small metal stitching repair that we carried out on the cylinder head of a Ford 1710 tractor built in 1984.

The cylinder head of this 3-cylinder, 1’400 cc (85 cu in), 84 mm bore and 84 mm stroke engine suffered from a crack close to one of the fuel injectors. The crack led to cooling water leaking into the combustion chamber. The cylinder head had been repaired before, by metal stitching, but not by us.

3-cylinder, 26 hp (19.4 kW), Ford 1710 tractor cylinder head

To permanently repair it, we carried out the following work on the cylinder head of this 19.4 kW (26 hp) engine:

Dismantling
Visual and Magnetic Particle Inspection (MPI)
Metal stitching of two cracks
Milling of the landing surface
Reassembly
Pressure testing

Metal stitching cracks inside various engines’ combustion chambers is something that we routinely do with excellent results. Our repairs are well able to withstand the challenging environment of up to 200 bars (2’900 psi) pressure and 350° C temperature that exists there. This time, the repair will last (unlike the earlier one, not done by us).

Magnetic Particle Inspection (MPI) reveals two cracks, extending from the earlier repair into the valve seat bores

Cracks repaired, valve seat rings reinstalled

After skimming of the landing surface — After pressure testing and skimming of the landing surface

The reassembled cylinder head prior to return to the customer — The reassembled cylinder head prior to returning it to its owner

The Benefits of a Global Footprint: Connecting Rod Repair “On the Fly”

24th March 2021

If your ships operate globally, then you benefit from relying on a service partner that has a truly global footprint. This post neatly exemplifies this fact.

The subject is an American-owned, 9’000 TEU container ship with an 82-bore main engine. The vessel experiences a crosshead bearing failure while crossing the Atlantic. We repaired it “on the fly” with a minimum of down-time:

During the last days of 2020, the vessel experiences a severe crosshead bearing failure close to Bermuda island. The crosshead pin and connecting rod are found severely damaged and are in need of repair or replacement. Our experts assess the situation and give remote assistance to the crew during removal of the connecting rod from the engine. Once that is done, the vessel continues its journey towards Europe with one cylinder cut out.
On 15 January 2021, the vessel arrives in Algeciras. The damaged connecting rod gets offloaded and is transported by truck to our workshop in Genoa.
It arrives at our works on 18 January and at once undergoes repairing. After completion of the repair, we ship the connecting rod by air freight from Milan, via Doha, to Singapore. It arrives in Singapore in the morning of 05 February 2021.
Our technicians in Singapore assist the crew to reinstall it. After a short and successful trial run, the ship continues its journey towards the South China Sea.

QuantiServ operates out of 15 locations that are strategically placed along major shipping routes or close to important ports. Wherever your ships go, we are never far away.

Corrosion protected and ready for dispatch

Metal Stitching on Historic Bridge in Washington DC, United States

29th January 2021

Our American colleagues have just completed metal stitching repairs on a historic bridge crossing the Chesapeake and Ohio Canal.

The Canal

The Chesapeake and Ohio Canal stretches over a distance of 297 km (184.5 miles) from Cumberland, Maryland, to Georgetown, DC on the US East Coast. It was constructed between 1828 and 1850 by approximately 35’000 labourers, mostly immigrants from Europe. Its purpose was to enable the shipment of coal from the rural but coal rich Allegheny Mountains to the much more densely populated regions and sea ports along the Atlantic coast.

The canal was operated from 1831 until 1924. While originally built for the transportation of coal, it quickly became an important lifeline for communities along its way.

The bridge we assisted restoring. Visible in the foreground is one of the canal's 74 lifting locks

Boats were used to ship agricultural produce and lumber to markets downstreams. They then returned loaded with manufactured goods. These boats typically did not have their own means of propulsion, but were pulled along by mules walking on towpaths located at either side of the canal.

One end of the canal, Cumberland, lies at an altitude 184 m (605 feet) higher than the other end, Georgetown. This meant that lift locks were needed – in total 74 of them were constructed. One of them is visible in the picture above, in front of the bridge.

In addition to the 74 locks, the canal also featured many other feats of early engineering. There were seven dams, about 240 culverts, a few aqueducts, a tunnel 950 meters (3’120 feet) long and, of course, bridges. A few of these bridges still exist today, such as the one that our metal stitching specialists proudly helped to restore.

Metal Stitching Work Performed

Exposure to the elements for over 150 years took its toll on the bridge structure. Cracks had developed in many of the vertical cast iron columns carrying the bridge deck. In all likelyhood, the cracks that were found were freeze cracks. Freezing temperatures are common in Georgetown from the middle of December until early March. If water enters one of the exposed, hollow columns and gets trapped there, then it very likely freezes during a cold winter night. Over time, the freeze/thaw cycles led to cracks.

All of the cracks ran in vertical direction. They had a cumulative lenght of 7’400 mm (25 feet). Our specialists sealed them with stitching pins and added perpendicular locks for extra strength. They then ground the locks and pins flush and made them blend in well with the weathered surface texture of the antique columns.

For the work to be carried out, a section of the canal had to be drained

The width of the cracks required pins with a large diameter to length ratio

Installation of stitching pins: Close to 1'000 were used for this project

In many locations, the cracks were wide open — On some of the columns, the cracks had caused a gap of up to 12 mm

Our specialists stitched over 7 meters of cracks — On this restoration project, our specialists stitched over 7.4 meters (25 feet) of cracks

Once completed, the repair blends in very well — The completed repair blends in very well

Stitching in progress — Metal stitching in progress: Stitching pins installed in an overlapping pattern

Locks were added for extra strength — Metal stitching in progress: Adding of locks, perpendicularly to the crack, for extra strength

Four-stroke Engine Block Metal Stitching and Crankshaft Machining

29th December 2020

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

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:

: Serious damage above crankcase door / camshaft space

: Missing piece size: 430 mm wide, 355 mm high and 150 mm deep

: Rendering of the damage. Data aquired through 3D scanning

: All damaged material removed by in-situ milling

: Newly fabricated repair patch

: Stitching in place of the repair patch

: Repair inside, prior to painting

: Stitching completed, view from the inside

: Remachining of the lower liner bore

: Stitching completed, new stud holes about to be drilled

: Repair is hardly visible and much less so when painted

: Completed repair, prior to painting

Flywheel In-situ Repair on the US East Coast

4th March 2019

Starting up a handymax bulk carrier’s 48-bore, two-stroke main engine with its turning gear engaged resulted in the turning gear shattered and in damage to 12 consecutive teeth on the flywheel.

The turning gear was damaged beyond repair and had to be replaced. Not only was its housing shattered but the planetary gears were completely destroyed too.

Faced with the costly and unpalatable reality of most likely having to replace the flywheel as well, the ship management company turned to QuantiServ for help. Always liking a challenge when we see one, we engineered and delivered a comprehensive solution that consisted of the following:

Inspection on board
CAD and FEA modeling to engineer an economical yet structurally very strong solution
CNC machining of repair inserts in our workshop
In-situ machining of the flywheel on board
Stitching the repair inserts in place

Our in-situ machining and metal stitching specialists carried out the work in February 2019, during the vessel’s port stay in Florida, without interfering in her schedule.

QuantiServ carries out a number of gearwheel repair assignments every year, mostly for industrial, marine and mining customers.

: Flywheel was damaged over 12 teeth

: CAD simulation, used for engineering a repair

: 3-D printed prototype of a repair insert

: Prefabricated repair insert

: Flywheel undergoing crack testing after repair

: The completed repair

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

15th August 2017

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.

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