Crankshaft deflections are measured to detect the misalignment of main bearings. The
misalignment occurs due to bearing wear or deflection of crankshaft. The horizontal and the
vertical misalignment are checked.
• The crank web of each unit is provided with a punch mark where the deflection gauge is to be set
for measurement. Clean the oil from the web & place the gauge in the marks. For additional
precaution, tie the gauge with a thin rope to avoid it from falling into the sump.
• Turn the engine to 30° after BDC & then set the gauge to “0” with slight pre tension.
Now turn the crank shaft in the ahead direction with the help of turning gear & take the deflection
gauge readings. The deflection gauge reading should be recorded in the gauging sheet.
• TDC -BDC readings give vertical deflection &
• Port – Starboard readings give horizontal deflection of the crankshaft.
The recorded readings are then interpreted in a graph & compared to the original graph to point out
the worn-out or deflective bearings which are causing crankshaft misalignment.
Last unit reading might be higher due to overhanging of the flywheel.
BP -Near Bottom Fuel p/p side (should be 0)
P – Fuel p/p side
S – Exhaust side
T – TDC
BS – Near Bottom Exh Side
