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Project

EMD R20-710G7B Main Engine Turbocharger & Gear Train Troubleshooting for AHTS Vessel in Namibia

Table of Contents

Background

Industry
Marine
Solution
Turbocharger & Gear Train Troubleshooting and Maintenance
Make & Model
EMD R20-710G7B
Main Engine
Asset
Anchor Handling Towing Supply Vessel (AHTS)

Summary About The Project

Neptunus carried out turbocharger and gear train troubleshooting and maintenance on the STBD EMD R20-710G7B Main Engine of an Anchor Handling Towing Supply Vessel in Namibia. The work focused on inspecting the turbocharger, rear gear train, front-end gear train, camshaft and related engine components to identify wear, damage and abnormal conditions. The scope also included water pump servicing, cooling system checks, exhaust valve timing, hotbox inspection, component repairs and replacement of selected parts. Pre-commissioning checks, engine trials, load trials and sea trials were carried out, with engine parameters monitored during operation.

Planning

  • Team Composition: Neptunus Service Engineer with technical expertise, supported by two local technicians.
  • Duration: 14 May 2025 to 09 June 2025
  • Work Scope:
    Turbocharger and gear train troubleshooting inspection and maintenance, including turbocharger removal and inspection, gear train inspection, camshaft and top deck inspection, water pump servicing, exhaust valve timing, component repairs, pre-commissioning and engine trials.

Procedure Carried Out

1. Turbocharger Removal and Inspection:
  • Engine isolated and jacket water drained before commencing the work.
  • Cooling pipework, solenoid, air intake duct and nose cone removed.
  • Turbocharger removed carefully for inspection.
  • Turbocharger impeller inspected and found free from abnormal rubbing or noise.
  • Turbocharger gear train inspected for wear, pitting and deformation.
  • Turbocharger drive gear showed moderate to heavy pitting.
  • Corresponding smaller turbocharger idler gear showed heavy wear and deformation.
  • Turbocharger components cleaned and inspected for serviceability.
2. Rear Gear Train Inspection:
  • Rear gear train inspected after turbocharger removal.
  • Existing camshaft gears were identified as previously repaired components.
  • Turbocharger drive gear and associated gear train components inspected.
  • Thrust washer condition inspected, including the broken retaining tang and evidence of washer movement.
  • Idler and carrier drive gears inspected and found visually serviceable.
  • Taper roller bearing inspected and found serviceable.
  • Gear backlash and thrust clearances checked after reassembly and found within specification.
3.Turbocharger Gear Train Overhaul:
  • Turbocharger gear train dismantled for inspection and maintenance.
  • New turbocharger idler gear and bushing installed.
  • New thrust washers, retaining plates and bolts installed.
  • Fasteners torqued and wire locked as required.
  • Turbocharger reinstalled with new seals, mounting gasket and bolts.
  • Gear backlash verified after installation.
  • Damper plate for the turbocharger mounting bolt fabricated and installed.
4. Engine Top Deck and Camshaft Inspection:
  • STBD and PORT Main Engine top decks inspected.
  • Camshaft followers, exhaust valve lobes, rocker arm rollers and related components inspected.
  • Wear marks identified on selected STBD camshaft components.
  • Camshaft lobes and roller surfaces inspected and lightly blended where required.
  • One worn roller replaced.
  • Damaged camshaft support retaining components repaired with newly fabricated retaining pins.
  • Further replacement of affected camshaft segment assemblies, bearings, dowels and fasteners recommended.
5. Water Pump and Cooling System Work:
  • Water pumps removed, serviced and reinstalled.
  • Cooling system filled and leak checks carried out.
  • Cooling water leakage identified at an aftercooler flange and water pump tell-tale area.
  • Aftercooler flange leakage rectified using a new gasket and sealant.
  • Water pump exchanged during troubleshooting.
  • New gaskets fabricated and installed as required.
  • Cooling system rechecked during engine operation.
6. Exhaust Valve Timing and Gear Train Inspection:
  • Exhaust valve timing checked on the STBD and PORT Main Engines.
  • Front-end gear train inspected.
  • Crankshaft axial play checked against the specified range.
  • STBD crankshaft axial clearance recorded at 0.018 inch.
  • PORT crankshaft axial clearance recorded at 0.014 inch.
  • Gear train components inspected for wear and serviceability.
7. Hotbox and Component Inspection:
  • Hotbox inspection carried out on both Main Engines.
  • Camshafts, rocker arm rollers, valve bridges, fuel lines, fuel racks and lube oil lines inspected.
  • Damaged hotbox door holding brackets repaired.
  • Exhaust valves, rotators, collets, bridge springs and valve seats inspected.
  • Fuel injection components inspected.
  • Injector height and fuel rack settings checked.
  • Crankshaft thrust play and connecting rod play checked.
  • Gauge lines and fuel distribution pipes inspected, with defective sections removed for replacement.

Recommendations

The first 100 running hours should be closely monitored for abnormal sounds, vibration and changes in engine parameters. Lube oil filters should be changed after the first 100 hours and inspected for particles, followed by a lube oil sample as recommended. Engine starting and stopping procedures should follow the manufacturer’s requirements, with close monitoring of lube oil pressure, jacket cooling water temperature and fuel dilution. The turbocharger drive gear should be replaced at the earliest opportunity, while the accessory and governor drive gears should also be considered for replacement due to the engine’s high running hours. Further monitoring of the camshaft lobe and roller condition is recommended.

Pre-Commissioning and Load Trials

Following maintenance, the engine was pre-lubed and cooling water was filled. Leak checks and lube oil flow checks were carried out before starting the engine. The engine was started and operated while monitoring lube oil pressure, cooling system condition, turbocharger operation and gear train noise. Both Main Engines were warmed up and speed was increased in intervals while operating parameters were recorded. Load trials and sea trials were carried out, with engine parameters found satisfactory and no abnormal operating conditions identified during the final trials.

Scope for Improvement

Considering the high running hours of the EMD R20-710G7B Main Engine, planned replacement of ageing accessory and governor drive gear components should be considered. The recommended camshaft segment assemblies and associated bearings, dowels and fasteners should also be planned for replacement. Maintaining critical EMD spare parts and special tools onboard can support faster troubleshooting and reduce downtime during future maintenance activities.

Conclusion

Neptunus carried out turbocharger and gear train troubleshooting and maintenance on the EMD R20-710G7B Main Engine installed on an Anchor Handling Towing Supply Vessel in Namibia. The work covered turbocharger inspection and maintenance, gear train inspection, camshaft and top deck checks, water pump servicing, exhaust valve timing, component repairs and pre-commissioning activities. Engine trials, load trials and sea trials were carried out after the maintenance scope, supporting the vessel’s continued operational readiness.

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