Oil Sample Was Heavily Diluted
Professional Skipper Magazine Issue 36 Nov/Dec 2003 (unedited)
I received a phone call a while back from one of my customers, a fleet engineer, in charge of a number of vessels based in and around Auckland.
An engine on one of their vessels had suffered a major drop in oil pressure. At the time I was taking oil samples on another of their vessels, which had four main engines. The vessel with the change in oil pressure had three engines, the port, starboard and a central engine. The port was the one that had suffered the oil pressure loss. I was asked to sample all three so that they could compare the results. Other than the oil pressure loss I understood that the engine had been running quite satisfactorily and had sounded no different than the other two engines. Once all three samples had been drawn they were sent away to the lab for analysis.
A couple of days later I rang the lab to follow up on another sample that I had sent to them. I wanted to confirm the amount of fuel dilution in the oil. The lab said the tested sample showed approx 9% fuel dilution but mentioned that it was not the only one that contained large amounts of diesel in the oil. They told me that the starboard sample from the commercial vessel mentioned above contained even more, almost double in fact.
I rang the engineer straight away to tell him he should contact the vessel and have the starboard engine shutdown. As there were two other engines in operation this was obviously not going to be a problem, but he asked about the port engine. At the time I only had a verbal from the lab about the starboard's 16% fuel dilution problem. The full results were due out that afternoon but I contacted the lab again to find that there were no issues at all with the port engine, which the fleet engineer was very happy to hear.
When the results arrived on my email that afternoon the only thing of note was the very high fuel dilution in the starboard engine. The viscosity (oil thickness) of the oil was also very low. As a result the oil was not offering the engine any protection, which could have resulted in the engine seizing at any stage. All other results from the three engines were well within acceptable limits. All the wear-metal counts were very low as were the levels of contamination. As far as the lab results were concerned there was no indication as to the reason for the oil pressure drop in the port engine. Other types of inspection work would need to be carried out to discover the cause.
Once the vessel was back in port the tappet covers were removed from the starboard engine. The reason for the fuel dilution problem was very obvious! All but one of the injectors was covered in oil, however one was lovely and clean. The seal between the injector and the internal pipe work had gone. The diesel was flushing the immediate area around it clean. The problem had not long started before we came on the scene so the crew had not had time to pick up any increases in the oil level on the dipstick.
Whilst the vessel was down the engineers decided to have a look at the port engine. The engines being mounted the way they were meant that removing the sumps was very easy. To their absolute amazement sitting in the bottom of the port engine sump was one of the main bearing caps. The bolts had come loose and the bearing cap had just dropped away. As there was no obvious signs of damage or wear to the bearing shell it was decided to remove the rest, including the big-end caps. None of the other bearing shells showed any signs of wear either. It was concluded that no damage at all had taken place as a result of the bearing cap dropping off. All other areas connected with the oil pressure were checked i.e. oil pump, seals etc. Once these other areas were checked and tidied up, the only answer left for the oil pressure loss was the missing bearing cap.
As there were no signs of wear or damage, the main and big-end bearing caps were all put back in place and the sump was reinstated. Once the work was completed the engine was run up to operating temperature and to top it off the oil pressure had returned to normal.
The fleet engineer was very happy with the process as the oil analysis on the starboard engine alone saved him thousands, possibly even tens of thousands of dollars. However, to my joy I was pleased that the oil analysis had showed no sign of wear before the sump on the port engine was removed. To this day we have continued to carry out oil analysis sampling before each oil change so that we can build up a history or trend with the wear-metal patterns. With the 9 samples to date there has been no sign of any bearing wear at all in the port engine, while the fuel dilution in the starboard went from 16% to less than 1% and has stayed that way ever since.
Written By Kelvin Hieatt
Managing DirectorMarine Diagnostics Ltd
