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Warning:
You can only determine the wear and tear delay time by using an additional tensile force
transducer (additional option 2 for the "Option 4" control unit).
With the tensile force transducer you can measure torques during the wear test as well as
measure the wear delay.
3.2.3 Conditions if the loads applied are extremely high
If loads are extremely high, no state of equilibrium occurs when the wear occurs. Instead,
the wear continues over a prolonged period of time, whereby the friction heat generated at
the contact surfaces combined with the high specific pressure (after a more or less long
period of time) leads to the 4 test balls being welded together (see Fig 3).
Fig 3
In most cases the welding occurs at the beginning of the 1-minute test.
Generally, the next lower load is referred to as the extreme-pressure property (lubricity) of
the lubricant. It is the maximum load at which no welding of the balls occurs within the 1-
minute test run.
A value of 320kg/340kg indicates that the respective lubricant just passes the 1-minute
wear preventive test at a load of 320kg, but fails the test at 340kg where welding occurs.
The VKA weld point cannot always be based on to determine the suitability of a lubricant
for gears subjected to extremely heavy wear. If required, the anti-wear properties of the
lubricant must be tested with the VKA-110.
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