75W90 Synthetic oil Blackened in Aluminium Gearbox
75W90 Synthetic oil Blackened in Aluminium Gearbox
(OP)
Hello, I am running an Aluminium Spur gearbox with 75W90 Synthetic oil around 200F temp in lab endurance test continuously.After 400 hrs the lubrication is failing.The oil is completely blackened out. The oil condition test shows that Phosphorus and Boron particles are burned out. There was significant sulfur content increased in the oil over the test duration. The housing innner surfaces are permanently blackened . Please let me know the reason for the increase in Sulfur content and housing blackening.Whether 75W90 Synthetic is not correct choice for this application. Thank You.





RE: 75W90 Synthetic oil Blackened in Aluminium Gearbox
you might like to look into this one
http://www.widman.biz/uploads/Transaxle_oil.pdf
So, you check the base spec. of your oil whether it's an API GL-4 or a -5 and then also the additives content.
On the blackening of the oil itself, you might contact the suppliers tech support on this, whether it is really worn out.
Regards
R.
RE: 75W90 Synthetic oil Blackened in Aluminium Gearbox
given the fact that it is completely dark indicates that there may be either thermal breakdown of some of the baseoils used or there may be heavy oxidation. both can lead to oil insoluble products that will form a layer on the gearbox housing and the gears themselves. additives for gear oils are usually a combination of sulfur and phosphor. when those additives are used to prevent gear damage their composition may change and as a result the previous ratio of sulfur to phosphor may also change.
could you be somewhat more specific about the type of oil used? "synthetic" is a very broad term that can encompass all types of fluids and fluid combinations and not all of them would be suitable as a base for gearlubricants.
RE: 75W90 Synthetic oil Blackened in Aluminium Gearbox
RE: 75W90 Synthetic oil Blackened in Aluminium Gearbox
On the sulphur, the check would be to look what kind of sulphur containing additives were in the oil in the first place and then, whether these additives disintegrated or by use changed their chemical state.
Could you pls. add information about the gear / rpm running of your application, and the specificalities of the failing of the lubrication?
RSVP
RE: 75W90 Synthetic oil Blackened in Aluminium Gearbox
Many of the lube oil additives described above are designed to produce a surface layer on the steel gears that inhibits adhesion between the contacting surfaces under marginal lubrication conditions, but only for limited periods of operation.
Here is an article that might help: http://www.machinerylubrication.com/Read/652/black...