ENGINE OVERLOAD, INLET AND EXHAUST VALVES, INJECTORS, FUEL SYSTEM OVERFLOW VALVE CONCERN

This document consists of the detection of engine overload. A issue in the area of inlet valves unit no 2, 4, 5, 6, 7 and 8. A issue in the area of exhaust valves unit 1, 2, 3, 4, 7 and 8. A issue in the area of injectors of unit no 3, 4 and 5. A issue in fuel system overflow valve of a Nigata 8L28HX Main Engine PS. A Hi, Raw, Ultra vibration and PV measurements were performed with vibration equipment, the results were analyzed.

1 INTRODUCTION

The main engine condition is based on the real load calculated by our measuring equipment and vibration an ultrasonic measurement collected. The fuel system overflow valve condition is based on the pressure readings taken during the engine operation. The data obtained from the engine analysis was processed, analyzed and compiled by a qualified professional analyst, resulting in the following recommendations:

  • Unit no 1 – Exhaust valve clearance has to be checked
  • Unit no 2 – Inlet and exhaust valves clearance have to be checked
  • Unit no 3 – Injector has to be checked, exhaust valve clearance have to be checked
  • Unit no 4 – Injector has to be checked, inlet and exhaust valves clearance have to be checked
  • Unit no 5 – Injector has to be checked, inlet valve clearance have to be checked
  • Unit no 6 – Inlet and valve clearance has to be checked
  • Unit no 7 – Inlet and exhaust valves clearance have to be checked
  • Unit no 8 – Inlet and exhaust valves clearance have to be checked
  • FO system overflow valve has to be checked
  • Engine load should be reduced to minimum 15% to protect the engine from immediate damage. (According to our data the engine is overloaded 107,9 %)

2 DEVELOPMENTS

2.1 THEORETICAL REFRENCES:

Early closing of the valve indicates a problem of excess clearance ore damage on the hydraulic tappets. Low compression pressure indicates a problem of injector clogging or poor atomization. Low pressure of FO indicates a problem in the overflow valve. The high load is the effect on the engine caused by the previously indicated problems.

2.2 VIBRATIONS SHOWN

Inlet valves Hi Freq Vib measurements acquired can be shown as follow:


Vibrations on inlet valve of unit no 2, 4, 5, 6, 7 and 8 are observed, much sooner than the other on the other units. As a conclusion of this analysis, it was recommended to check the inlet valve clearance.

Exhaust valves Hi freq vib. measurements acquired can be shown as follow:


Vibrations on exhaust valve of unit no 1, 2, 3, 4, 7 and 8 are observed, much sooner than the other on the other units. As a conclusion of this analysis, it was recommended to check the exhaust valve clearance.

Pressure measurements acquired can be shown as follow:


FO pressure is much lower than the pressure from the sea trials. As a conclusion of this analysis, it was recommended to check the FO system overflow valve. According to our data the engine is overloaded (107%).

3 SHIP ENGINEERS CHECKS

The engine was cooled down then the cylinder head no 1, 2, 3, 4, 5, 6, 7 and 8 caps were disassembled to access the rocker arm device and injectors. The inlet and exhaust valves clearance were measured by a feeler gauge and correctly adjusted. Injectors were removed, cleaned and checked injector nozzles will be replaced as soon as spare parts will arrive. FO system overflow valve was checked and replaced.

4 REMEASURE

After the adjustment was made the engine was restarted (at lower load as recommended) and new FO pressure was remeasured and new vibration measurements of inlet and exhaust valves were taken. The results can be shown as follow:




It is clearly shown that after the adjustment the valves are closing at the same moment and that the FO pressure is in limit.

5 CONCLUSIONS

It can be concluded that the diagnosis obtained from the measurements and the data analysis was correct. The crew was informed to maintain the reduced load on the engine. Until new parts will be available. Further measurements will be done as soon as possible. If no actions where performed a serious damage could put this engine out of order for a long period of time.