Crankshaft Care Key to Vessel Profitability
Mark van Schaick Marine Services is a relatively new company, based in
Schiedam (Port of Rotterdam) specializing in crankshaft repair, repair of
engine and industrial parts, technical consultancy, and marine and industri-
al spare parts.
The company has capacity at its workshop for grinding crankshafts up to
20 ft. (6 m) on a lathe built by Naxos Union. As a result of a co-operation
with Mitchell Shackleton in the U.K., crankshafts up to 39.5 ft. (12 m) can
be repaired. Every possible kind of crankshaft can be checked, ground, pol-
ished, straightened, hardchrome-plated and hardchrome-ground. If a client
requests, the company will undergo inspection by certification and classifi-
cation societies. Repairs can also be carried out on turbine parts, engine
blocks, connecting rods and pistons.
Avoid Serious Crankshaft Damage
As maintenance is becoming more important with high output diesel
engines, especially when it comes to crankshaft failure, the company offers
the following advice to potential clients:
In the past, the material used for a crankshaft was, for example CK40,
which after a bearing failure and overheating does not show extreme crack-
ing or increase in hardness. This meant that such shafts could be ground
undersize and re-used without any restriction.
Today, engines have high-tensile steel crankshafts with non-hardened or
hardened running surfaces; after a bearing failure and overheating most of
these shafts are beyond repair. The non-surface-hardened shafts react on an
overheated bearing with very hard spots up to Brinell 600 (about Brinell 300
is allowed), bending and often severe cracks. The available undersizes are
normally not enough to salvage the shaft.
Surface-hardened shafts, on the other hand, lose their hardness when a
bearing gets overheated and will often crack as well. This is also a reason
for rejection because the hardness is totally gone in particular locations and
will not come back when the shaft is ground undersize.
Rejection of the shaft can be avoided by keeping an eye on the following
points:
•Keep the oil in good condition, take samples and have them examined.
•Check the big ends of the connecting rods and repair them if ovality
exceeds the limit.
•Check the ovality of the crank pins and the wearstep between the webs. If
there is a serious wearstep between the crank webs do not fit new bearings
without removing it.
•Check the torque of the connecting rod bolts and main bearing cap bolts.
Use a calibrated torque-wrench.
•Renew bearings according to maker's specifications.
•Renew connecting rod bolts according to maker's specifications.
•Make sure that the engine has no misalignment.
•Check vibration damper according to maker's specifications.
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May, 2002
ISLAND BOATS, INC.
ALUMINUM CATAMARANS & UTILITY CRAFT
VESSEL SHOWN IS A 60' x 20' USCG CERTIFIED 100 PAX EXCURSION/FERRY
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• COMPETITIVE PRICING TO EAST/WEST COAST BUILDERS
• BOATS UNDER CONSTRUCTION (2) 65' UTILITY LANDING CRAFT
PASSENGER FERRIES • SHIP TENDERS •
EXCURSION VESSEL • PILOT BOATS • CREW BOATS
ISLAND BOATS, INC.
6806 HWY 90 EAST NEW IBERIA, LA 70560 PH: 337-560-4483 FAX: 337-560-4473
EMAIL: islandboats@eatel.net
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