A limit value is a value intended to indicate whether the amount of wear particles found in the oil is still tolerable or whether an oil change or other measure must be carried out. Limit values for wear are given in mg wear metal per kg oil or in ppm.
A limit value for dust, water or other contaminants in the oil is relatively easy to define for engines, machines and plants. However, there are no generally applicable limit values for the permissible proportion of wear metals in oil.
Too many factors influence these limit values for wear. Even the engine and machine manufacturers provide information on limit values only extremely rarely. Only a complex consideration of all influencing factors and the entire spectrum of all detected different wear metals allows a specification and the evaluation on the basis of limit values.
OELCHECK uses a device-specific matrix when evaluating an oil sample. In it, the respective machine element is defined as precisely as possible. The operating time of the oil, the operating hours of the machine, a possible oil change or a major refill are taken into account as well as the oil type.
This is compared with limit values from an OELCHECK database, which draws on the findings of over 4 million OELCHECK analyses carried out internationally. From this interaction, the experienced OELCHECK tribologists obtain the basic information for the final personal assessment of the oil sample. With OELCHECK, experts - not a computer - comment on the wear metals detected.
Like a blood sample in medicine, each oil sample should be considered on its own or as part of a trend analysis.
Basically, when estimating the values, the following must be taken into account:
- Everything is o.k. if the determined value is lower than the lower table value.
- Everything is critical if the determined value is above the highest table value.
- All values must be seen in interaction if one of the values is in the intermediate range.
It should also be noted that:
- the larger the oil quantity
- the shorter the operating time
- for motors: the lower the rpm
- for hydraulics: the higher the operating pressure
- for gears: the higher the circumferential speed
the smaller the limit values for wear metals!