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Purifiers, a Simple Description:
We all know that purifiers are very high speed centrifugal separators, which are usually used to separate fuel and lubricating oil from water, other liquids, and solids. There may be two to four heavy fuel oil purifiers and two lubricating oil purifiers. The numbers may vary depending upon the type of ship and the machinery details.
These purifiers are usually kept in a separate room called the “Purifier room." I sailed on an oil tanker that had two fuel oil and one lube oil purifier. Out of the two fuel oil purifiers, one was out of operation for a very long period of time as there were no spare parts. Since only one of the two purifiers was operational, there was always a risk of running out of fuel if the running purifier fails. When I joined the vessel, I discussed with the 2nd Engineer regarding trying out the stand-still purifier. We both made a work plan and after completing watch routines, we both started the job with a work permit. We checked the gear case oil level and checked the freeness of the bowl. We also opened the top cover of the purifier, and checked the assembling and condition of the bowl. Everything was perfect and the decision was made to start the purifier.
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As we started the purifier, it slowly gained momentum and after few minutes, as the speed was about to reach rated value, there was a huge cloud of smoke originating from the gear case. I immediately activated the emergency stop button. We both ran away from the purifier room and waited until the purifier came to a stand-still.
After ten minutes, we both approached the purifier to find out the cause. The gear case door was opened up and surprisingly we found the gear case to be absolutely dry. The gear case was full of metal pieces and the gear teeth completely grinded and shattered. We both discussed about how this incident could have happened. Upon investigation, we found that the gear case sight glass was coated with oil stain as the machinery was kept stand-still for a long period of time. We both assumed that the oil level was sufficient on seeing the oil stain from outside the gear case.
Actually there was no oil in the gear case, and once the purifier was started, without lubricating oil, the gears shattered. Upon investigation we came to a conclusion that the position of sight glass was fitted wrong. It is quite obvious even a very experienced Marine Chief Engineer will commit such a mistake while fitting the sight glass.
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The Sight Glass Design:
The sight glass has parallel lines. These lines are usually fitted in a horizontal fashion by everyone. But nobody had observed or noticed the manufacturer's manual. The manual clearly indicates that the sight glass must be fitted with the lines in vertical fashion. What happens when fitted horizontally? When fitted horizontally, the oil level may match one of the lines, and thus does not appear to be seen correctly.
But when fitted with the lines in vertical fashion, there always forms an intersection between the horizontal oil level line and the vertical sight glass line, thus forming a corrugated design enabling the oil level to be seen clearly. The pictures are attached with this article to understand the difference. Thus we informed this issue to the Chief Engineer, who exclaimed “This is a costly lesson, but a good one." The management immediately sent warning letters to the other ships inquiring about the position of the sight glass.
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Alfa laval Manual.
My personal Pictures.