I've been studying the effects of bad oil against rotating machinery, to be specific on this particular gearbox which operates 24 hrs with input speed of 1500 rpm and gear ratio of 18. I've been looking closely at this machine for almost 6 month now and I have to say, it psychs me every time I think about it. It started off when I found a chipped or a better a way to say it, a spalled gear tooth.
Off course it didn't look right. In no time oil quality issues came right up in my mind as I found lotsa pitting points on other teeth as well. Bad oil will surely contribute to this kinda problem but why oil turns bad? It's only been a year and why is it that bad? When I asked the OEM (in my case is SUMITOMO, damn japanese, can you please design a more reliable gearbox?) they said, "Just follow the manual" and thank god their english are good, I could understand 'em clearly but that didn't help at all man!!!
It has to be the oil, it has to be the oil... I said to myself again & again. Micropitting can be caused by a too-thin oil film i.e a higher viscosity oil is needed and/or oil is badly contaminated. I forgot to mention, the oil foamed badly when we opened up the gearbox which suggests i) air entered the gearbox from loose piping or broken seal ii) too much detergent effect: detergent cleans the formation of debris from combustion at the gear teeth, which later suggests a more thicker oil is needed & iii) contamination.
So, I guess it's time for oil analysis now. We sent 3 sampels which two of them are the used oil (1 year old, used oil) and the other one is a fresh-from-an-unopen-barrel oil for base reading. SUPrisingly, the new oil is as bad the used oil!!! I mean contamination wise! TAN is slightly high than the used one but you have to remember Acid Number curve againts time is bath tub shape meaning it starts off high, goes down and goes back up again. So TAN is not the issue here. Hmmm Petronas didn't do a good job when blending this oil. So I came up with an idea or better yet a program which we'll only accept oil with cleanliness cert i.e QA/QC cert to ensure the new oil is fresh! One day will be implemented.
Now, WAY FORWARD?? Now we change the oil once in every two month and using a fully synthetic oil which posses a better Vicosity Index compared to Mineral Oil. It's expensive but worth every penny. So whenever you find spalling teeth, act quickly as the gearbox will fail in no time. It might be months, weeks... ummm maybe days. Stay sharp guys, eyes on the oil!!!
Just wanted to share; knowledge is power
It has to be the oil, it has to be the oil... I said to myself again & again. Micropitting can be caused by a too-thin oil film i.e a higher viscosity oil is needed and/or oil is badly contaminated. I forgot to mention, the oil foamed badly when we opened up the gearbox which suggests i) air entered the gearbox from loose piping or broken seal ii) too much detergent effect: detergent cleans the formation of debris from combustion at the gear teeth, which later suggests a more thicker oil is needed & iii) contamination.
So, I guess it's time for oil analysis now. We sent 3 sampels which two of them are the used oil (1 year old, used oil) and the other one is a fresh-from-an-unopen-barrel oil for base reading. SUPrisingly, the new oil is as bad the used oil!!! I mean contamination wise! TAN is slightly high than the used one but you have to remember Acid Number curve againts time is bath tub shape meaning it starts off high, goes down and goes back up again. So TAN is not the issue here. Hmmm Petronas didn't do a good job when blending this oil. So I came up with an idea or better yet a program which we'll only accept oil with cleanliness cert i.e QA/QC cert to ensure the new oil is fresh! One day will be implemented.
Now, WAY FORWARD?? Now we change the oil once in every two month and using a fully synthetic oil which posses a better Vicosity Index compared to Mineral Oil. It's expensive but worth every penny. So whenever you find spalling teeth, act quickly as the gearbox will fail in no time. It might be months, weeks... ummm maybe days. Stay sharp guys, eyes on the oil!!!
Just wanted to share; knowledge is power
2 comments:
gearbox tu load dia apa?
Its for cooling tower fan. Motorspeed 1500 rpm gear ratio is 18:1... so output shud be around 80 i guess. chipping gearteeth... has to be lubrication bro.. no doubt. if it is overloaded the designed motor for that specific gearbox shud be fully/over loaded as well. Have given a thought about it, but it comes back to lube.. have u experienced this kinda thing?
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