Can we make a general statement that the higher the base oil viscosity of an open gear grease, the more effective is the lubrication effect? This is the stand often taken by the grease suppliers to sell a grease with higher base oil viscosity (and higher price!). I would rather go by the specific test results of a particular grease than its base oil viscosity alone.

One would expect a better film thickness and damping effect with a grease of higher base oil viscosity. But I have observed several instances where an open gear drive operated quite satisfactorily when the grease having a 1000 cSt base oil viscosity was replaced with a grease of 500 cSt base oil viscosity.

Also, are there any apparent effects of higher base oil viscosity on the performance of the grease spray system ?

Dear Barun,
I think its a general staement of comparision that the performance levels of higher base oil viscosity is better than that of a same compisition of lower base oil viscosity.
But of course the perfomance levels are not exhustively listed in any datasheets and neither they are conducted here.
Simulation are not as accurate as field results and also exhaustive field results are missing.
I think in the 2nD PARA we are only talking about adequacy of 500cst Vs 1000cst.
Its not of better performance.
I have some test results done for comparision between lubes of diffeent viscosities and brands done by BHP Australia in their lab as well as a write up on spary Lubricants from Svedala and can share with you if you like.
regards
Arupanjan

I have been wondering a bit on this topic myself as the plant I work in has large roll dryers with the trunion rollers and the spur gears spray lubricated with ISO VG 46 AW hydraulic fluid. Would anyone consider this an adequate lubricant for such a heavy load application. At least there isnt alot of thick lube to clean up around the base.

Is the spray continious? and of course AW 46 Oils I have my reservation, but the best persons are OEMs of the machine to permit the minium ISO VG range of the oils for this oil.
Well u might be saving on clean up and disposition but some one has to check the temp of the gear tooth flank amd vibration of the drive system before commenting.

Interesting topic....and without a doubt controversial.
The debate between the residual compounds and the greases and the synthetics and the PIB fortified open gear lubes has been ongoing for a long time.
As was pointed out some of the proponents will claim that their product is the best for your application, bar none. If you ask them for the engineering calculations and the standards by which they base their statements most will be unable to provide much meaningful data. What they offer up is a list of people who are using their product, testimonials from other users that may or may not know the difference in lubrication performance. A customer that might have gotten a 2X increase in the MTBF of their pinions but it is still 1/2 of industry average life. Long on hyperbole but low in fact.
In my maintenance life I have seen the tried and true asphaltic residuals used with success. I have seen some grease used with success and even a heavily fortified PIB mineral oil perform well. But I have never seen 1 product family that was suitable (the best) for all applications.
There is a school of thought that suggests that if the lubricant is too thick then it has the effect of causing the generation of localized pressure ridges that cause the effect of plastic flow. The rational is that the load is focused on a localized point instead of being spread out across the gear face.
I would suggest that serious consideration be given to assessing and understanding the particular requirements of the application and then performing the calculations necessary to at least provide a starting point from which to specify the requirements.
So to the question "can we generalize by saying that {in open gear grease} that a higher viscosity is better? My opinion is yes because most North American greases use base oil viscosity's that do not match up with fundamental viscosity requirements for the applications that I have performed the calculations for. You will find that most of these greases carry a fairly high amount of solid additives, obviously to fill in the void that the base oil cannot.
Will consensus ever be reached on this subject? I doubt it, as long as there are no definitive testing protocols that can simulate and hence guarantee performance standards.

Re the issue of the AW ISO 46 oil. If the rim speed is sufficiently high enough then an ISO 46 might work. What kind of life are you getting from the spur gearing and are the failures related to scuffing or pitting across the face and hence lube viscosity or for other reasons. Understanding your failures will help you to determine the suitability of the lube. A 46 seems low but...........

re: the sprayability of different greases, sprayability is a function of the synergies between the base oil and the thickener system as well as the recipe followed when making the grease. Generally the higher the combination of NLGI grade and base oil the higher the volume (ratio between lube and air) and velosity of air that is required. I have had success with a Spraying Systems vendor in the past to run some tests for us with different lubes (minimal or no charge). You tell than the capabilities of your system and provide a sample of the old and new lube and they run the comparisons and recommend the nozzles etc suitable for the new lube.

hope this helps

regards........

This message has been edited. Last edited by: Alan Wallace,

First of all I must agree with Allan and thank him for some insight as well as his own views on that.
Secondly this is a very very serious topic of Debate in India, specially in the cement industry.
Third I would comment the following and also require inputs from the forum to learn and perfect the subject and share with every one what I learn.
We now see in Indian Market the following products
residual compounds, the greases and the synthetics from some multi national company- some are black due to high concentration of solids, max 10%, and some are over coming the prblem of low viscosit and high solids with high base oil viscosity to get the same property and performance, which are transparent and making the gear surface inspection meaningful, which is of absolute necessasity. Its also a fact that there might have a 2X increase in the MTBF of their pinions but it is still 1/2 of industry average life. Long on hyperbole but low in fact.
I think AGMA gives a guide line based on the PCD of the gear and Face width of the pinion and whether, the spray is on the gear or pinion the minimum amount of Lube necessary for a particular type of Lube that is the viscosity of the grease either in Cst or SUS and so also the OEM specifies according to the peripheral speed and gear material. And that’s how the calculations are based. If there is any thing else I would like to know that form the forum. The asphaltics have success but are banned now due to Environmental as well as health reasons as well the revision of Design parameters in gear materials.
As far a thickness of the Lubricants, if we are mentioning NLGI grade – Higher base oil viscosities are generally with low consistency i.e. 00-000, and if the spray is uniform then there is no chance of localized pressure as the knowledge goes and hence plastic deformation should not be the issue.
Considering the gear is new and peripheral speeds are high low viscosity greases may be used as hydrodynamic conditions are achieve able in high speeds like in mills of certain speeds about 20- 25 rpm. And I also Agree with Allan a higher viscosity is better for protection.
As in north America, so also in Europe, the base oil viscosity is supported by higher solids, but the potential danger remains on the purity as well as type of solids. The higher the base oil viscosity lower is the percentage of solids – is that right Allen?
As far as simulation and test methods are concerned, there could be 2 the modified FZG Test of A/2.76/50 and not A/8.3/90 for reasons of channeling in higher viscosity sump lubrication giving misleading results. There are some suppliers in India proposing A/8.3/90 as the test and THE CREDIBILITY of this test in open gear systems is questioned by FZG also as per information because of the test results and field experiences are contradictory.
A SRV test was hence done by ball on plate, in Australia to get the pitch line stress effect as well the co-efficient of friction vs. time and wear and results were plotted gave a better insight on performance capabilities and was in commensurations with the field result.
Yes Again ISO- 46 speed is an issue but the but remains
and so also the comment on sparybiliy is fully agreed with the opinion of Allen.
Any further input please on this issue.
regards

I think looking at takifier levels and anti corrosives could be just as important. As well as how long its hanging in there throughout the service life.

This message has been edited. Last edited by: astrixstar,

Yes they are important and regarding how long......
US Steel retention test is important.
regards
Arupanjan

Dear Arupanjan,
Dr. Barun has started an interesting debate.
Unfortunately there are no international specifications for Open gear lubricants. Each company tries to propagate their products indicating their benefits/advantages and the customer has to make a choice based on experience, cost, data claimed by lubricant supplier, OEM approval and its performance in other plants.
This could be because of different operating conditions.
You may be aware that in India we are trying to develop the specifications for Open Girth Gear Lubricants.We have studied analysed no. of lubricants and they vary a lot.Yet each one claims to be the best.
The subject of higher base oil viscosity better or not is really a babatable issue.What Ifeel is that depending upon the requirement(?), the base oil viscosity should be chosen.

Dear Mr Vijay
Any specific reason why the mail was addresses to me only?
Having asked that I would like to put forward my observations and comments:
Open gear Lubes are sold in a similar way as any other lubes or products.They are specified in similar parametrs like any other grease or oils by international standards like ASTM or DIN.
But unfortunately in Indian Industry, there are very little conclusive data on the performance of each product, either from users or independent bodies, though we have seen these lubs in the country for almost last 20 yrs or more,
I will be obeliged if you could share the process of developing the specifications for Open Girth Gear Lubricants. and also the procedures & results on-"We have studied analysed no. of lubricants and they vary a lot.Yet each one claims to be the best".

How ever I have gone through some elaborate procedures and logics of testing of OGL by SVEDALA-USA cuurently Nodberg and BHP Mineral systems of Australia.I have also seen good comments made by Alan, who seems to have worked with open ideas, in his elaborate note on this subject.
I think Svedala, BHPs are not less knowledgebale on this subject and we need to trust them, if we have to make an advancement on this and look at the global experiences.
regards
Arupanjan

This message has been edited. Last edited by: Arupanjan,

No special reason why it was addressed to you Mr. Arupanjan.But you have been very active in these discussions.
Yes I agree with you that there are no sufficient data of performance of the product against the operating conditions/mill specifications.
You are aware that there are products from KLUBER, Reiner, OKS, Croft, Shell, Castrol etc.each having different specifications.One of the product has Weld Load 400 Kgs.yet claiming to be highly efficient.
NLGI India Chapter has been working to arrive at uniform specifications for these products like ISI specn. for Gear Oils, Turbine oils etc.
But its always nice to get the views from others on these subjects.
Thanks.
Vijay

I know the product which is having 400 Kg of weld load and since that product is designed for a unidirectional rotation machine 400 kg is adequate. Other Products are designed to meet the requireemt of both unidirectional and reversible rotational products.
I think they dont sell this product of 400 kg in the reversible load application.They have a product of 800Kg for that application. Is that right?
Any way as I said and also reconfirm that these products are tested and evaluated by OEMs and only a basic engineering is required to evaluate the products.
Other info is Renires have been taken over by Fuchs and Kraftt has been taken over by Molykot
Regards

quote:

write up on spary Lubricants from Svedala

Dear Mr. Arupanjan Mukherji.

Could you send me the details of write up on spary Lubricants from Svedala on tradingdubai@gmail.com