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Project

NIIGATA 6L28AHX Engine Cylinder Head Overhaul for Oil Rig in India

Table of Contents

Background

Industry
Oil & Gas
Solution
Cylinder Head
Overhaul
Make & Model
NIIGATA 6L28AHX
Main Engine
Asset
Drilling Rig

Summary About The Project

Neptunus carried out a cylinder head overhaul of a NIIGATA 6L28AHX Engine installed on an oil rig in India. Before the maintenance team arrived, the Engine had overheated and was shut down by the customer. Water leakage was also reported from the water jacket side. The overhaul scope included removal and dismantling of all cylinder heads, pressure testing, dye penetrant testing, removal of exhaust valve seats, cleaning of the cylinder block, piston and connecting rod assemblies, cylinder liners and water jackets, and inspection of the camshaft and fuel injection components. All cylinder heads were found to have leakage from the exhaust seats and injector sleeves during hydro pressure testing, while cracks were identified in the exhaust seat pockets during dye penetrant testing. The piston pins, piston crowns, connecting rods and camshaft were inspected, with the relevant components found satisfactory or in acceptable condition as recorded in the report. Cylinder liner jacket water rings were installed with new O-rings, and exhaust manifold flange gaskets were replaced.

Planning

  • Team Composition: Neptunus team of 4 led by the Team Leader
  • Duration: 21 October 2024 to 28 October 2024
  • Work Scope:
    Cylinder head removal and overhaul, cylinder head pressure and dye penetrant testing, exhaust valve seat removal, piston and connecting rod inspection, cylinder liner and water jacket cleaning, cylinder block and camcase cleaning, cylinder liner honing, rocker arm servicing, manifold cleaning, gasket and O-ring replacement, fuel injection component inspection, and crankshaft cleaning.

Procedure Carried Out

1. Cylinder Head Removal and Dismantling:
  • Removed all injectors and rocker arm assemblies.
  • Removed the cylinder heads, piston and connecting rod assemblies, and cylinder liners.
  • Dismantled all cylinder heads.
  • Cleaned all cylinder heads.
  • Removed all exhaust valve seats from the cylinder heads.
2. Cylinder Head Inspection and Testing:
  • Carried out pressure testing of all cylinder heads.
  • Hydro pressure tested all cylinder heads at 5 kg/cm².
  • Leakage was found from the exhaust seats and injector sleeves of all cylinder heads.
  • Carried out dye penetrant testing on the combustion surface areas of all cylinder heads.
  • Cracks were identified in the exhaust seat pockets of all cylinder heads.
3. Piston and Connecting Rod Inspection :
  • Removed and cleaned the piston and connecting rod assemblies.
  • Heavy rust residue was found on the piston crowns.
  • Carried out dye penetrant testing of the pistons, piston pins and connecting rods.
  • Piston pins were found satisfactory.
  • Pistons were found satisfactory.
  • Connecting rod small ends were found satisfactory.
  • Reassembled the piston and connecting rod assemblies using the OEM procedure.
  • Oiled and secured the piston and connecting rod assemblies properly.
4. Cylinder Liner and Water Jacket Servicing:
  • Dismounted the cylinder liners.
  • Heavy rust was found on the top areas of the cylinder liners.
  • Removed the cylinder liner jacket water rings.
  • Cleaned all cylinder liners and water jackets.
  • Cleaned the cylinder block and camcase thoroughly.
  • Sent all cylinder liners to the main workshop for honing.
  • Mounted the cylinder liner jacket water rings back on the Engine with new O-rings.
5. Exhaust and Intake Manifold Servicing:
  • Disconnected and cleaned the exhaust and intake manifolds.
  • Found all union couplings in damaged condition.
  • Replaced the gaskets of all exhaust flange manifolds.
  • Inspected the manifolds and found them in normal condition.
  • Secured the manifolds properly in a safe place.
6. Rocker Arm Servicing:
  • Dismounted all rocker arms.
  • Rust residue was found on the rocker arm of Unit #1.
  • Dismantled and cleaned all rocker arms.
  • Assembled and secured all rocker arms properly.
7. Camcase Inspection:
  • Cleaned and visually inspected the camshaft.
  • Camshaft condition was found to be satisfactory.
  • Cleaned the camcase cover and installed it back on the Engine
8. Fuel Injection System Inspection:
  • Dismounted all fuel injectors and kept them in a safe place.
  • Cleaned and inspected the fuel injection unions and pipes on their inner surfaces.
  • Fuel injection unions and pipes were found to be satisfactory and secured properly.
9. Crankshaft Inspection:
  • Initially cleaned the crankshaft.
  • Rust was observed on the crankshaft web of Unit #5.
10. Water Jacket and Assembly Work:
  • Cleaned the water jacket.
  • Mounted the water jacket back on the Engine with new O-rings.
  • Secured all dismantled Engine components properly in a safe place.

Recommendations

The NIIGATA OEM maintenance schedule should be followed strictly for all scheduled Engine maintenance activities. The Engine should be closely monitored after overhaul for abnormal sounds, vibrations, operating parameters, and other indications of abnormal operation. Lube oil filters should be replaced after the first 100 running hours following the overhaul, and the filters should be inspected for abnormal particles. A lube oil sample should be taken after the first 150 running hours for oil analysis, and any abnormalities identified through the analysis should be addressed immediately. Engine starting and stopping procedures should follow the maker’s specifications, with particular attention given to lube oil pressure, jacket cooling water temperature, and fuel dilution.

Pre-Commissioning and Load Trials

The Work Completion Report does not document post-overhaul engine starting, pre-commissioning activities, or load trials. Therefore, no post-overhaul trial results are included in this case study.

Scope for Improvement

The overhaul inspection identified several areas requiring attention, including leakage from the exhaust seats and injector sleeves of all cylinder heads, cracks in the exhaust seat pockets, heavy rust on piston crowns and cylinder liner areas, damaged manifold union couplings, rust on the rocker arm of Unit #1, and rust on the crankshaft web of Unit #5. The report also identified that the NIIGATA OEM maintenance schedule was not being followed, required special tools were not fully available onboard, and emergency spare parts were not available onboard. Maintaining the required special tools and emergency spare parts onboard, together with following the OEM maintenance schedule, can support more effective maintenance and improve Engine reliability.

Conclusion

Neptunus carried out a cylinder head overhaul of a NIIGATA 6L28AHX Engine for an oil rig in India. The work included cylinder head removal and dismantling, hydro pressure testing, dye penetrant testing, exhaust valve seat removal, piston and connecting rod inspection, cylinder liner servicing, water jacket cleaning, manifold servicing, rocker arm cleaning, camshaft inspection, fuel injection component inspection, and crankshaft cleaning. All cylinder heads showed leakage from the exhaust seats and injector sleeves, while cracks were identified in the exhaust seat pockets during dye penetrant testing. Piston pins, pistons, connecting rod small ends, and the camshaft were found satisfactory as recorded in the report. Cylinder liners were sent for honing, while new O-rings and exhaust manifold gaskets were installed as part of the maintenance work. The report also highlighted the importance of following the NIIGATA OEM maintenance schedule, maintaining required onboard tools and emergency spare parts, and closely monitoring the Engine after overhaul.

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