SKF TKGT 1, Инструкция по эксплуатации

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21 SKF TKGT 1
3.5 Oil bleeding test
Base oil makes up 60-95% of a grease. As base oil in grease continuously bleeds out
(although the rate of bleeding gets slower and slower with time), grease dries out. The
time scale for this process depends on a number of factors such as operating temperature.
This process is called ageing.
Base oil in greases has a certain kinematic viscosity expressed in mm 2 /s or Cst. High
temperature could promote its oxidation and thus increase its kinematic viscosity.
The amount and viscosity of the base oil should not change drastically within the advised
relubrication interval.
These are possible causes for a change in oil bleeding properties:
A lower bleeding might be due to (used compared to fresh)
•
Loss of base oil (generally accompanied with an increase in consistency).
• Base oil oxidation leading to base oil viscosity increase due to high temperature.
• Big amount of hard particles.
• Mix of greases.
A higher bleeding might be due to:
•
Grease can not keep base oil into its structure due to intensive shearing or vibrations.
(especially true for sheared polyurea greases).
• Oil contamination from neighbouring systems.
• Mix of greases.
• Grease with poor mechanical stability.
3.5.1 Principle of operation
A ixed amount of grease is put on a piece of the blotter paper provided. By heating this
paper for two hours, the base oil will be released from the grease and create an oil stain
on the paper. By measuring the diameter of the stain formed, calculating the bled area
and comparing with the area given by an unused fresh sample, the change in bleeding
properties can be evaluated.
Bled area
Heat
2 hours