Checking and Disassembling Piston


Tools Required
  1. Piston ring expanding pliers.
  2. Adapter
  3. Extension
  4. T-handle
  5. Wrench socket
  6. Ratchet
  7. Feeler gauge
  8. Lifting gear and hemp rope
  9. Note pad
MAINTENANCE  

Remove and check piston at specified intervals. The length of periods between overhauls depends upon operating conditions, i.e in engine load, fuel used, quality of combustion, on engine lubrication and cooling. Compression rings should normally not be removed for checking, as rings are subjected to severe stress during removal and refitting. Check pistons and liner wall for effectiveness of lubrication.
The compression ring and oil control ring are to be replaced every 10.000 operating hours, unless damage as per work card necessitates replacement at an earlier stage.

Carbon deposits on piston crown
Clean piston ring grooves
Starting Position
Piston has been removed and placed on wooden support.

SEQUENCE OF OPERATION
Checking
  1. Check condition of the piston and piston ring.
  2. Clean piston of carbon deposits, taking care not to roughen the surface of the piston crown. Cautiously clean running surface.
  3. Measure axial clearance of ring in their grooves, note down measurement and enter them in the engine log.
  4. Measure shoulder clearance between piston crown and piston skirt at 4 point evenly distributed over entire circumference and note them down. For admissible shoulder clearance rates and admissible deviation of tares from amount the various measuring points.
  5. Using piston ring expanding pliers, remove  the piston rings, inspect them closely and renew if required.
  6. Carefully clean groove in piston and check wear.
  7. Install rings on piston, using piston ring expander pliers, measure groove clearance and record in engine operation log.
Note: While installing a used piston in a cylinder liner from the original, new compression rings and a new oil control ring must be used at any rate.The engine must then be run in again.

Dismantling
Piston has been removed and cleaned on outside, shoulder clearance has been measured.
  1. Remove piston pin an connection rod head.
  2. Loosen four nuts and unscrew.
  3. Slip hemp rope through piston pin bore in piston skirt and attach, lift off and cautiously deposit. When lifting off, attention has to be paid to the stud bolts and the thrust pieces.
  4. Carefully clean piston crown and piston skirt. Inside of cooling spaces must be cleaned to be metallic-bright. Oil passages are to be cleaned with compressed air. Check parts for damage (cracks).
  5. If required unscrew studs form piston crown.
Note: Operation of engine with intensely contaminated lubricating oil results in increased coke deposits in the cooling space of the piston.  

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