|Type Of Ship||: Car Carrier|
|Engine Make||: Wartsila – W8L32|
|Engine running hrs||: 34,027|
The ship crew were testing the Main engine (4 Stroke engine) as a part of the routine test at low to moderate engine power. During such test, there was an alarm for low cooling water pressure and subsequent high jacket water temperature. The engine tripped on high jacket temperature. Engine crew inspected the engine, cooling system and found nothing abnormal. The Engineers attempted to re-start the engine and the soft iron cylinder head gasket in unit # 8 blew out. Unit #8 was opened and a new gasket installed after cleaning the deposits. After assembling and warming up the engine, an attempt was made to re-start the engine. This time unit #1 cylinder head gasket blew out. Thus, a decision was made to open up all cylinder heads and change the cylinder head gaskets. The engineers suspected cooling water leak and thus decided to There was also a suspect of leaking cooling water into the combustion space which could have caused the cylinder head gasket to blow out. All cylinder heads were decided to be removed and pressure tested for leaks.
- Ship Staff removed all the cylinder heads.
- Unit #1 & Unit #8 big end bearing removed for inspection.
- New connecting rods used for unit #1 & unit #8 with the same piston.
- All piston rings renewed in unit #1 & unit #8.
- The fuel injectors were inspected suspecting that the fuel accumulation in combustion chamber could have caused the cylinder heads to blow out.
- It was found that the fuel injectors were not in good condition with:
- Low Opening Pressure
- Internal Leak
- Dripping Nozzle
- Clogged Nozzles
- All fuel injectors overhauled and pressure tested.
- All cylinder heads pressure tested and all found intact. No loss of pressure.
- Dye penetrant test was done on cylinder heads and no cracks observed.
- As per Engine maker’s guidelines, when a hydraulic lock is suspected, the connecting rod straightness has to be checked. Since this was not possible onboard, the spare connecting rods were used.
The ship manager decided to seek for engine expert’s opinion to solve the problem. The engine expert came onboard and upon inspection of all the parts, he inspected the engine entablature. To his surprise, when he held a cylinder head stud, it was loose and free to rotate by hand. All the jigsaw fell in place and the engine expert asked for a feedback on the cylinder head tightening pressure and loosening pressure. The Chief Engineer reported that the hydraulic nuts got loosened at a very low pressure at around 400 bar when compared with a pressure of 520 bar. The engine expert checked for the cylinder head studs whether they are “bottomed” and found that they were not. Thus, the root cause for the problem was established. The cylinder head studs were tightened to 400 NM as per engine maker’s guidelines.
The engine was restarted and checked for operating parameters from no-load to full load and there were no problems observed. The engine was stopped and started several times to check for cylinder head gasket condition and all were found intact.
- The Engineers failed to observe the loosening pressure when loosening the cylinder head nuts. If the hydraulic nuts open at too low pressure, then this needs to be investigated.
- Failure to Adhere to Maker’s instruction manual or service letters.
- Failure to attend to loose cylinder head studs caused the cylinder head gasket to blow up.
About the Author:
Mr. Holger Jacobsen, the “Engine Expert” has spent over 23 years with MAN Diesel & Turbo, managing both field and technical services in Australia and Singapore. He was the Head of Diesel Engineering at Teekay Shipping in Vancouver BC. In 2009, he started the Emission Services for Wartsila in Canada and has been with Wartsila for 6 years. With both MAN Diesel & Turbo and Wartsila’s tag over his name, he has a ‘Midas touch’ to solve/consult on any diesel engine problem. With over 30 years of working experience on diesel engines of any size/make, We honour him with the title – the “Engine Expert”.
Write to Holger through MFAME.
Do you Have an Engine Problem? Write to Holger at: firstname.lastname@example.org
Incorrect tightening, due to dirty thread (ei. Stud, jack, bolt)