Can a grease for a particular application be more than one NLGI number? e.g. if two different companies have an open gear oil and one has an NLGI 2 and the other is NLGI 1 shall this have a great significance?

This depends also a little bit on the RPM's and 'stand-still' periods of the gears I guess. Can you describe your application a bit more detailed?

Steve,
Technically speaking an open gear oil cannot have a NLGI grade number. As the NLGI test refeers to a specific test conducted on a grease to determine it's worked consistency. However in keeping with the direction of your question, For every specific operational context and operating there is an optimal lubricant selection. This would provide you with your desired component life, noise level, heat generation tolerance etc. If for instance you optimised and determined the product to be a R&O in an NLGI 1.5 grade range then either a 1 or a 2 would be fairly close. Unfortunatly it is seldom the case that the operating conditions are directly corralatable to the test sequence parameters. The biggest considerations you need to give to the different NLGI grades (assuming the base oils charastics to be equal) is the pumpability at the vearing temperature conditions and also the slumpability of the NLGI grade in the application.
Hope this helps....
regards........

NLGI - National Lubricating Grease Institute. An NLGI number can be "roughly" compared to an ISO oil viscosity. The number represent "penetration" of a standard cone into the sample of grease. A NGLI 1 would have a penetration of 310 - 340 in a 5 second time frame. On the other hand a NLGI 2 would have a penetration of only 265 - 295, which suggests the # 2 is thicker then a #1. From one company to the next, they should use the same test to arrive at the NLGI number. The NLGI number is only one of the factors involved in sourcing grease. Consider grease base, additives, operating parameters; temp/load/environment. NLGI number can have some impact in high demand applications. Hope this helps.

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Originally posted by Steve:
Can a grease for a particular application be more than one NLGI number? e.g. if two different companies have an open gear oil and one has an NLGI 2 and the other is NLGI 1 shall this have a great significance?

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Technically there is no great significance while considering applications such as open gears. As forum members mentioned, it is the pumpability that would be a cause between NLGI 2 and 1. NLGI 2 is harder to pump comparing to 1. But many open gear applications do not require product circulation, rather direct spray/injection with help of mechanical feeders.
Kumar e mail kumartr2@yahoo.com

Kumar

If the question is specifically directed to open gears I have the following opinion,
Yes we can use different NLGI Grades of greases if there is a spray system and it can handle the same for example if the spray system can spray NLGI#0 we can also use NLGI #00, means any thing below the capibility of the system .
Assumtion made is that it has a spray system like from Lincoln, Woerner or Delimon.
How ever we need to make a consideration if there is adequate air pressure to spary the grease or not.
Again this is specific to open gear drives.
pl feel free to ask any other doubts. I am working on this subject for some time now.
regards

Tackiness is a significant factor in open gear application, as well as the viscosity of base oil (considering that the additives level is the same), and type of base oil which determines initial VI).

John