Ask the Expert

the Expert

Q:

Is there a recent pie chart showing the breakup of the world grease usage, by sector, by soap type?

A:

Please consult the NLGI Grease Production Survey - available for purchase on the NLGI website - to get a break-down by thickener type. Here’s the link: https:// www.nlgi.org/products-page/2014-nlgi-greaseproduction-survey/

As far as usage by sector, it’s a fairly even split between industrial and transport. Beyond that, they would need to contact a market research firm for more detailed information.

Q:

I have a 1.5 fluid ounce tube of Permatex WL-9 White Lithium Grease. Is it safe to use this grease on the gear that is exposed when the ice storage bin is removed from the freezer? The grease is used to keep the gear from sticking when the bin is removed. If this grease is not safe what do you recommend?

A:

NLGI does not endorse any commercial products. Permatex WL-9 White Lithium Grease appears to be an industrial grease and would likely not perform satisfactorily at the operating temperature of an icemaker. We suggest you contact the manufacturer of the refrigerator/freezer/icemaker to get their product recommendation for the application described.

Q:

I’ve been running some grease corrosion tests in accordance with ASTM D4048 and getting quite varying results on the same test sample. The main variable I can see is the amount of cleaning at the end of the test - should this just be a simple wipe? The grease leaves an oxidised coating behind and it is difficult to determine if I’m removing the grease coating or tarnish. Mainly I get some black streaking / spotting with a coppery undertone. There is no red / green / or brassy discolouration. Would this be a 1b or a 4? Any advice with this test method would be greatly appreciated.

A:

“ASTM International, formerly known as the American Society for Testing and Materials (ASTM), is a globally recognized leader in the development and delivery of international voluntary consensus standards. ASTM D 4048 method is the responsibility of the ASTM D.02. G0 Lubricating Grease sub-committee which is split into 7 sections. Section G.01 is directly responsible for Chemical and General Laboratory Tests which includes ASTM D4048-10 “Standard Test Method for Detection of Copper Corrosion from Lubricating Grease”. Inquiries about this test can be directed to Joe Kaperick, the chair of Section G.01, at joe.kaperick@aftonchemical.com.”

Q:

Please help with finding conversions from civilian greases to military greases. The approved grease list that I have from Dexter Axles lists greases such as: Conoco Phillips Multiplex RED #2, Kendall L427 Super Blu, Citgo Lithoplex MP #2, Lithoplex CM #2, Mystik JT-6

High Temp Grease #2, Exxon Mobil Ronex MP, Mobilith AW2, Mobil 1 Synthetic Grease. There are many more listed. Where can I find what those greases cross to in military numbers such as MIL-G-24508?

A:

The greases that you have listed are all commercial or industrial products. Those products typically do not carry military approvals. To find a list of products that are approved against a specific military specification, we suggest you consult the Assist database at http:// quicksearch.dla.mil/. That application contains a database of approved products, and is maintained by the US military.

Q:

I run a tree stump grinding service using diesel powered stump grinding machinery. The pillar block bearings supporting the machines spinning cutter wheel at a max speed of 1500 rpm are subjected to a constant bombardment of soil grit, stones, etc. It is as though a grit-blasting nozzle is permanently aimed at the bearings whenever the machine grinds out a tree stump. This cutter wheel is also subjected to extreme intermittent shock loads throughout an eight-hour workday. I have been on a quest in search of the most appropriate grease to lengthen bearing life and hope you can assist in that regard.

A:

First and foremost, always follow the lubrication recommendations of the manufacturer of the equipment. That being said, and without clear guidance from the equipment manufacturer, we recommend a heavy-duty grease with the following general characteristics:

NLGI Grade 2

Base Oil Viscosity 460 cSt @ 40°C

Thickener Type Lithium or Lithium Complex

Additive Package Extreme Pressure additive

A grease with the above characteristics should provide satisfactory protection to the bearings in the equipment.

Q2:

Thank you so much for your fast response. I have contacted the manufacturer (J.P. Carlton Co. “sales@ stumpcutters.com”)awaiting a reply.

Heat build up over an eight hour period is an issue. What ASTM D2266/D2596 results should I be looking for with your suggested grease characteristics. Would CS thickener with 5% moly be excessive and what is the next upward base oil viscosity.

A2:

If the bearings tend to run hot, a product containing a lithium complex thickener is recommended over the simple lithium thickener. The lithium complex thickener has higher temperature capability. With regard to D2596 (Four-ball EP), we recommend a minimum weld point of 250 kgf (kilograms force). A weld point of 315 kgf (the next higher load stage) would be even better. For D2266 (Four-ball Wear), we recommend the product have a value no higher than 0.6 mm. A product containing a calcium sulfonate thickener could also be considered for this application, but molybdenum disulfide (“moly”) is not recommended in this case. Although moly can be beneficial in shock load situations, for rolling element bearings turning at 1500 rpm, moly is not typically recommended. It can congregate at roller ends, cage pockets, etc. in the bearings and take out clearances, causing the bearings to run hot. It can also lead to sliding rather than rolling of the bearing elements.

Other things to consider: What product is currently being used? Based on the properties of that product and the level of service it is providing, we may be able to give a better generic product recommendation than done previously. If the bearings are running hot, a lower base oil viscosity of 220 cSt @ 40°C may be a better choice for this application. Finally, a product based on a synthetic base fluid (such as polyalphaolefin (PAO)) may provide lower bearing temperatures than a mineral oil based product of similar viscosity at 40°C.