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I was invited by Tom Astrene of TLT to write a response to the
July 2010 TLT article (Ref. 1). My rebuttal — “In Search of a Fatigue
Limit: A Critique of ISO Standard 281:2007” — was published
in Tribology and Lubrication Engineering, TLT, August
2010 edition (Ref. 10). While this article is also available online,
I will attempt to summarize the essence of my response.
For the lubrication of open gear drives
used in different industrial applications
such as cement and coal mills,
rotary furnaces, or where the sealing
conditions are difficult, semi-fluid
greases are often used in preference to
fluid oils. For girth gear applications
the greases are used with a splash or
spray lubrication system. The selection
of such greases influences pitting lifetime
and the load-carrying capacity of
the gears, as well as wear behavior
End users and OEMs frequently specify
"lubed-for-life" mounted bearings, thinking the lubed-for-life bearings will deliver the same life — without lubrication — as bearings that
currently require periodic lubrication. The truth is it depends on many factors, and only a detailed review of the application and testing will provide a more accurate answer.
In this century’s complex, ever-
changing world of manufacturing,
such capabilities as hardware and software expertise, effective location and distribution, business savvy and
yes, even luck, are some of the
cardinal requirements for running
a successful business.
Varying installation requirements for worm gears, as, for example, when used in modular gear systems, can necessitate grease lubrication - especially when adequate sealing for oil lubrication would be too complex. Such worm gears are being increasingly used in outside applications such as solar power plants and slew drives. While knowledge about the operating conditions is often appropriate, the basic understanding for load capacity and efficiency under grease lubrication is quite poor. Investigations done at FZG and sponsored by FVA/AiF are shown here to give an impression of the basic factors of load capacity and efficiency. The results of the investigation indicate a satisfying quality of calculations on heat, load capacity and efficiency based on characteristic parameters of the base oil with only slight modifications to the methodology known from DIN 3996 or ISO TR 14521.
The 8th International CTI Symposium on Automotive Transmissions, HEV and EV Drives took place in Rochester, Michigan from May 12-15. The event kicked off with its popular introductory seminar "Basics and Practice of Automotive Transmissions."
Grease lubrication has clear advantages over oil lubrication: Grease does not leak easily; it has sealing properties; and it protects bearing surfaces from corrosion. Its disadvantages are grease-life limitations and a limited cooling ability. Moreover, in some applications there is a risk of grease starvation, which leads to reduced
lubricating films. However, if the right grease, sealing system and/or lubrication system are chosen, then grease lubrication offers clear benefits. This article summarizes aspects of grease lubrication mechanisms in rolling bearings.
Despite posting its slowest quarter
since early 2007, AWEA remains
optimistic that the wind industry can
and will work successfully with the
revolving doors in Washington.