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EP grease best for?

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A arielMember
Hello, Injun22.

There are many kinds of greases, and they are made from different viscosity base oils, the lower viscosity grades will make low consistency greases, higher viscosity levels will make higher consistency greases, the trick to choose the right grease IN MOST CASES is this. High speed, low viscosity. Low speed, high viscosity. High load, High viscosity. By high and low viscosity i mean the base oil which the grease is made of, ( the thickener nature is important also, however the most widely used is lithium 12-hidroxystearate ) and as far as I know the best EP aditive is molybdenum disulfide.
J johnmMember
Consistency of a grease does not depend nor is influenced in any way by viscosity of the base oil. Viscosity only affects the amount of thickeners added to achieve certain consistency of the final product.

Ranking efficiency of EP additives could be done only on the application basis; i.e. whether you count speed, load, shock-load, operational and/or environmental temperature, etc.
A arielMember
Hello John, i have read your reply and i have been reviewing my notebooks in order to realize if i need to retreat or stand in my words... i found this:

"The viscosity of the base oil used in making a grease is important since it has some influence
on the consistency, but the grease consistency is more dependent on the amount and type of
thickener used."


I am quoting "Engineering tribology" Stachowiak & Batchelor Butterworth Heinemann 2001 pp 67 chapter 3 "lubricants and their composition"

( I hope that giving the data info i will not face any sanction related to copyright. My apologies to mods if that is not the case.)

Altough i could have been clearer, i am not saying nonsense, i do not think that i was wrong in my previous statement.
J johnmMember
quote:
Originally posted by Ariel:
Hello John, i have read your reply and i have been reviewing my notebooks in order to realize if i need to retreat or stand in my words... i found this: "The viscosity of the base oil used in making a grease is important since it has some influence, but the grease consistency is more dependent on the amount and type of
thickener used."...

I wish, and I suppose you do too, that Stachowiak & Batchelor Butterworth Heinemann were more specific regarding the statement that base oil viscosity has "SOME INFLUENCE" on grease consistency. What influence, and in which way they made the influence? Such wage statement is similarly confusing like when someone says, for example: “It is particularly effective at low pressure”. WTH that means? Is it better at 20 psi, 300 psi, 700psi, 1000 psi, or what, because every single one could be considered low pressures by different folks? Or similar statements about a “high pressure”, or low or high temp, or high or low speed or load. Good authors should be specific when describing factors influencing final products or processes, and how they do it. This way, they have just threw a bone for us to debate about it.

Bottom line is (the way I see it), unless a base oil viscosity is not higher than a grease of NLGI 0000 consistency (maybe bitumen), viscosity of such oil only influences the amount of thickener needed for the targeted consistency of final product (grease).
A arielMember
What is viscosity?
In few words, viscosity is the resistance of a fluid to flow or move over itself.
What is a grease?
A grease is base stock oil and additives trapped inside a tridimensional porous structure.
What is consistency?
Consistency is the resistence of the grease to be moved.

Lets play with those definitions.

A low viscosity oil is easyly moved, it flows over itself with ease... a medium or high viscosity oil will do, but slowly. If we trap these oils within a tight structure, the same tight structure, which one will scape faster?
I think that the one with the lower viscosity will do.
If this one is poured within an tighter structure, we can see that it will try to scape, however it will be slower this time. Let´s put it within an even tighter structure... really really tighter... perhaps then it will match the scape speed of the one with the higher viscosity.

Do you agree with this hypothetical experiment?

If so, let´s move on.

You have 3 cilinders:

1: 90 mL ISO VG 32
2: 90 mL ISO VG 100
3: 90 mL ISO VG 460

Now, for each, add 10 grams of thickener, soap, clay or whatever you want, and 5 mL polar activator.

Stir them, let´s say 1 hour.

You have made grease, far from the best but grease in the end.

Do you think that the consistency will be the same?

At this time you have stated that viscosity lacks relevance in the consistency, will you stand that argument?

On the other hand, if you make a grease NLGI 4 from a base stock iso 32, how long will it last till it bleeds the oils totally? if the thickener was clay, tell me what you have after the oil is gone WITHIN your equipment. Clay... a lot of clay.
Would you have the same results if instead an ISO 32 you use an ISO 460.. or 680 or 1000?

I really appreciate the time you spend reading this. Please, i want to hear your comments.
J johnmMember
quote:
Originally posted by Ariel:
What is viscosity?
In few words, viscosity is the resistance of a fluid to flow or move over itself.
What is a grease?
A grease is base stock oil and additives trapped inside a tridimensional porous structure.
What is consistency?
Consistency is the resistence of the grease to be moved.

Lets play with those definitions.

A low viscosity oil is easyly moved, it flows over itself with ease... a medium or high viscosity oil will do, but slowly. If we trap these oils within a tight structure, the same tight structure, which one will scape faster?
I think that the one with the lower viscosity will do.
If this one is poured within an tighter structure, we can see that it will try to scape, however it will be slower this time. Let´s put it within an even tighter structure... really really tighter... perhaps then it will match the scape speed of the one with the higher viscosity.

Do you agree with this hypothetical experiment?

If so, let´s move on.

You have 3 cilinders:

1: 90 mL ISO VG 32
2: 90 mL ISO VG 100
3: 90 mL ISO VG 460

Now, for each, add 10 grams of thickener, soap, clay or whatever you want, and 5 mL polar activator.

Stir them, let´s say 1 hour.

You have made grease, far from the best but grease in the end.

Do you think that the consistency will be the same?

At this time you have stated that viscosity lacks relevance in the consistency, will you stand that argument?

On the other hand, if you make a grease NLGI 4 from a base stock iso 32, how long will it last till it bleeds the oils totally? if the thickener was clay, tell me what you have after the oil is gone WITHIN your equipment. Clay... a lot of clay.
Would you have the same results if instead an ISO 32 you use an ISO 460.. or 680 or 1000?

I really appreciate the time you spend reading this. Please, i want to hear your comments.

You got it all wrong. Your theory about flow of oils of different viscosity is correct, but it has nothing to do with grease, because they are still oils. Your other theory based on adding fixed amounts of thickeners to oils of different viscosity has no practicality, because you would end up with greases of deferent NLGI ratings, therefore, it is like comparing apples to oranges. The real comparison can be made only to grease of the same consistency. For example, to make grease with certain NLGI consistency, let's say NLGI 2 for the sake of the argument; grease made from low viscosity oil would contain greater amount of thickener, while grease made of high viscosity oil would contain less amount of thickener. That is a fact. It is also a fact that thickeners generally do not lubricate; oil in grease does. It is also a fact that greases with higher base oil viscosity exhibit greater load carrying characteristics, providing that neither grease contain EP additive.
G greasespecMember
Ariel,

Where you got sidetracked is that you can have an NLGI 1 grease with a 32 base oil viscosity, an NLGI 1 grease with a 150 cSt base oil and a NLGI 1 with a 460 base oil viscosity. All of them with the same consistency grade and though with different base oil viscosities.

That was meant by John, as I understood, in that the consistency grade is independent in a product with the oil viscosity. Alea jacta est.
S shivaMember
Nice discussion. Started with EP grease went on to ingredients of grease, its consistency and ended with EP.

I support John's arguments and ofcourse he gave the facts only. I would like to add some more points here.

"Grease making is an art & not science: This is an age old argument. Some agree some disagree".

SOME INFLUENCE:
Oil viscosity has some influence. right. If you go further i mean type of oil. Paraffinic, Naphthaneic & aromatic. They have marakable influence. Its all about solvency effect. FOr eg: for a particular grade of grease (same thickener), aromatic type requires less soap quantity than paraffinic type oil.

One cannot explain the consistency of grease just with base oil viscosity and with one type of soap. Consistency of a grease (for eg NLGI-2) depends on many factors. Type of soap, type of oil, process parameters, even additives (nature/dose) etc.... Well.. i would like to briefly touch on this. Lets make two type of greases (Al complex & BaComplex): take known qty of oil (same type & same viscosity) and take same quantity of both Aluminium complex soap and Barium complex soap. Now you will end up in different NLGI-grades. THis tells you base oil viscosity and soap quantity alone can not explain/determine the consistency of grease.

Normally for low speed high load- base oil with higher viscosity and for high speed low load -oil with lower viscosity work better. when you talk of high temperature, apart from oil viscosity (ofcourse high VI) type of soap plays significant role.
John, by the way what is that NLGI-0000 (i never heard about it) You have introduced this grade?. (hahaha... just kidding)

Cheers

Shiva
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