Hole in Piston Causes Major Accidend in Engine
In this post on Hole in Piston Causes Major Accidend in Engine, I will write about an actual life incident that has taken place on board a ship. This incident is the horror story of a piston failure. Readers will learn about the consequences of the negligence of an Engineer in reacting to the warning signal given by the mist detector.
Accident description
Accident took place at about 6 pm. Not long after, the staff had left the engine room for the day.It was lucky that no fatal injury took place due to this crankcase explosion. This explosion lifted and buckled the engine room floor plating and blew the spare parts store door (two decks above the crankcase). The frame blew the oil mist detector off the engine and caused extensive lighting, trunking, paintwork, and crankcase relief valve doors. The workshop door was buckled and de-laminated the control room door where shards of glass got embedded in adjacent woodwork.
On investigation, revealed that the cause of the crankcase explosion was the hole in the piston crown of No. five cylinders. Through the hole in the piston, combustion gases passed to the crankcase and ignited the oil mist.Further investigation observed the oil puddle on top of the piston, with a pen lying next to the crack sealing. Burn away was excessive on the piston crowns, with # 1, 6, and 8 out of tolerance. (No. 6 and 8 piston crowns were also cracked).
The hole in the piston crown has been by erosion due to improper fuel injection. Examination of all the other pistons also revealed the erosion effect with intensive cracks on the centre of the crown. There was an accumulation of carbon deposits of around 3mm, which could have compromised the cooling of the piston.
Fuel Valve Examination
Examination of the fuel valves revealed the following.
Blockage in the holesInvestigators observed enlarged Nozzle holes.Injection opening pressure was 45 bars below the standard injection pressure.Fuel injection was taking place in the form of a jet due to the enlarged holes. No proper atomization was taking place. This jet injection was causing the overloading due to poor combustion.
The purchaser didn’t purchase the nozzles from a genuine sourceDuring the investigation of crankcase relief valves, investigators found the improper assembly of the valves with defective flame arresters. Due to the jam operation of the relief valve after opening, remaining in the open position would have been the reason for the secondary explosion.There was a signal from the mist detector of the engine five seconds between the first abnormal indication- Engine governor fault and the Engine cylinder # 1 outlet high temperature. Due to the short period between the first indication and explosion, it was suspicious about the slowing down of the engine by the monitor fast enough to avoid the crankcase explosion.
Reasons for the Accident
During the investigation of crankcase relief valves, investigators found the improper assembly of the valves with defective flame arresters. Due to the jam operation of the relief valve after opening, remaining in the open position would have been the reason for the secondary explosion.There was a signal from the mist detector of the engine five seconds between the first abnormal indication- Engine governor fault and the Engine cylinder # 1 outlet high temperature.
Due to the short period between the first indication and explosion, it was suspicious about the slowing down of the engine by the monitor fast enough to avoid the crankcase explosion.
Piston seizure due to insufficient clearance.Seizure due to lack of lubricationDry running damages due to lack of lubrication caused by fuel floodingOverheating seizureAbnormal combustion damagesMaterial fusion by piston crown meltingPiston crown and combustion recess cracksFracture in-ring landHydraulic locksHole in the piston crownPiston seizure due to use of incorrect Piston Piston crown erosion Piston ring fracturePiston pin fractureFailure due to Piston pin circlipSeizure in the piston pin whole
Importance of Piston maintenance
Improper care of the Piston can cause severe damage to the Engine and associated engine parts—most of the failures in the engine area are due to piston failures. Every engine manufacturer provides guidelines for the proper maintenance of the Piston. Most of the Accident Due to | Hole in Piston have been due to the use of non-genuine components.
Piston failures are also due to the improper maintenance of fuel injection equipment. In this present piston failure, the cause of failure has been due to improper combustion. During the investigation, found the Nozzles were of inferior quality. The fuel flooding has caused a significant accident.
How to prevent catastrophic Piston failures
Unfortunate catastrophic failures cause the high cost of repairs apart from the downtime of the machine. Prevention of such devastating loss is with the following careful steps.
To inspect the pistons during overhaul. Carry out the NDT testing of pistons for crack detection. Avoid continuous high load on the Engine.Monitor the exhaust parameters to detect the fault in the combustion process.Inspect the piston cooling system during maintenance.Proper inspection of the piston lubrication system and to replace the defective nozzles for the piston cooling.Never follow the pound-foolish penny-wise formula.Avoid local procurement of critical spares of any machine.Never use the spare part without the proper inspection and stamp of the inspecting authority.Stop the Engine immediately in the event of a knocking sound from the Engine.Always use the proper grade of lubricating as per the suggestion of the Engine manufacturer.Carefully analyze the lubricating oil report—especially the metallographic analysis.Check the tightness of the piston plugs as per the schedule. In MAN B&W, the case of piston failure has been in the past.
Plugs have fallen due to the aging of glue applied on the thread of the plugs. Clean the spaces below the piston crown adequately as per the scheduled maintenance.Piston crown measurement is to be carried out by the unique piston crown measuring tool.
Detection of Piston Overheating
High cooling return temperatureVapor lock in the cooling system with increased noise.High crankcase mist detection by the mist detectorChange in color with dry patches of piston and exhaust valveSmell and smoke from the Engine.High smoke from the crankcase breather line.
Blog Conclusion
I hope the post on Piston’s failures has been helpful to the readers. The above-written suggestions are from the author’s experience as a marine Engineer and an expert with the Original equipment manufacturer.
Good Luck!!!
