Question

With regard to large 2 stroke engine:

(a) Explain, how can the cooling spaces within a cylinder jacket be examined without withdrawing the cylinder liner?

(b) To what parts of a cylinder jacket would you give attention after removing an old cylinder liner prior to fitting a new one?

(c) What periodic attention must be given to the scavenge air space and piston-rod packing (stuffing box) at the bottom of a cylinder liner?

Answer 1

Part (a)

Examination of cooling spaces in a cylinder jacket without removing the liner

Cooling spaces can be examined by the following methods:

Borescope / endoscope inspection
Inserted through cooling-water inlet/outlet connections or inspection plugs to visually check for:
- Scale formation
- Corrosion
- Cracks
Hydrostatic pressure test
The jacket-water system is pressurised to the specified test pressure to detect:
- Leakage
- Hairline cracks
- Weak joints
Cooling-water analysis
Monitoring pH value, chloride content and iron content gives an indication of:
- Internal corrosion
- Possible liner or jacket leakage
Temperature monitoring
Abnormal temperature rise or uneven temperature distribution indicates:
- Blocked cooling passages
- Scale build-up
Flow-rate comparison
Reduced or uneven jacket-water flow suggests:
- Fouling
- Partial blockage of cooling passages
Part (b)
Parts of the cylinder jacket to be inspected after removing an old liner (before fitting a new liner)
After removal of the liner, close attention should be given to the following areas:
- Liner landing faces (upper and lower)
- Check for:
  - Cracks
  - Fretting
  - Distortion
  - to ensure correct seating of the new liner.
- Cooling-water spaces
- Inspect for:
  - Scale
  - Rust
  - Sludge
  - and clean thoroughly to restore efficient heat transfer.
- O-ring grooves / sealing faces
- Examine for wear, corrosion or damage that could lead to cooling-water leakage.
- Tie-rod holes and stud seating areas
- Look for cracking or deformation due to stress concentration.
- Cylinder jacket bore
- Check for ovality, corrosion pitting or erosion that may prevent correct liner alignment.
Part (c)
Periodic attention to the scavenge air space and piston-rod packing (stuffing box)
Scavenge air space
- Regular cleaning
- Remove oil sludge, carbon deposits and debris to reduce the risk of scavenge fires.
- Inspection of scavenge drains
- Ensure drains are clear and effective to prevent oil accumulation.
- Checking scavenge ports
- Look for signs of:
  - Broken piston rings
  - Scuffing
  - Excessive oil carry-over
- Fire detection and safety devices
- Inspect scavenge fire flaps, drains and alarm systems for correct operation.
Piston-rod packing (stuffing box)
- Inspection of sealing and scraper rings
- Ensure effective separation between:
  - Scavenge air space
  - Crankcase oil
- Leakage checks
- Excessive leakage indicates worn rings or incorrect ring tension.
- Drain condition monitoring
- Observe drain oil for contamination, which may indicate stuffing-box ring failure.

✓ Verified Model Answer (Text Solution)

Examination of cooling spaces in a cylinder jacket without removing the liner

Cooling spaces can be examined by the following methods:

Parts of the cylinder jacket to be inspected after removing an old liner (before fitting a new liner)

Periodic attention to the scavenge air space and piston-rod packing (stuffing box)