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:

 

Flywheel In-situ Repair on the US East Coast

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.

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.