High-quality, NSF H1 approved grease
Diagram 1 The SKF traffic light concept
Each SKF Food Line Y-bearing unit is prelubricated for life with a non-toxic foodgrade grease, based on a PAO oil which contains an aluminium-complex soap as thickener (food industry approved NSF H1). This high quality synthetic grease is odourless and tasteless, leaving food unaffected.
Do not use Unreliable performance (use only for short periods) Reliable performance, i.e. with predictable grease life
Temperature [°C]
Broad temperature range Approved for use in all food and beverage processing equipment, SKF food-grade grease has a temperature range from –45 to 150 °C. († diagram 1)
–45 +20
+150 +270
LTL
HTPL HTL
LTL
Low temperature limit
LTPL
LTPL Low temperature performance limit HTPL High temperature performance limit HTL High temperature limit
Extends bearing life SKF food-grade grease offers advantages that help extend bearing life, including: • Excellent internal and external bearing corrosion protection • High aging resistance for extended lubricant life
The SKF traffic light concept Based on the exclusive SKF traffic light concept, the temperature range over which the grease lubricating the SKF Food Line Ybearing units can be used is defined by four temperature limits schematically illustrated in diagram 1 in the form of a “double traffic light”. The definitions of the extreme temperature limits are the following: • The low temperature limit (LTL), is the lowest temperature at which the grease will enable the bearing to be started up without difficulty. • The high temperature limit (HTL) is given by the grease dropping point. The dropping point indicates the temperature at which the grease loses its consistency and becomes a fluid. Operation at temperatures below the low temperature limit and above the high temperature limit is not advised as shown in diagram 1 by the red zones1). The recommended temperatures for reliable bearing operation are given by the following SKF values: • The low temperature performance limit (LTPL). • The high temperature performance limit (HTPL).
1) Despite
grease suppliers indicating the specific values for the low and high temperature limits in their product information, SKF recommends using these low/high temperature performance limits for reliable bearing operation.
8
It is within these two limits, the green zone in diagram 1, where the grease will function reliably and grease life can be determined accurately. At temperatures above the high temperature performance limit (HTPL), grease will age and oxidize with increasing rapidity and the by-products of the oxidation will have a detrimental effect on lubrication. Therefore, temperatures in the amber zone, between the high temperature performance limit and the high temperature limit (HTL), should occur only for very short periods. At temperatures below the low temperature performance limit (LTPL), the tendency of grease to bleed decreases and the stiffness (consistency) of the grease increases. This will ultimately lead to an insufficient supply of lubricant to the contact surfaces of the rolling elements and raceways. Since ball bearings are easier to lubricate than roller bearings, the low temperature performance limit is less important for ball bearings. Short periods in this zone, e.g. during a cold start, are not harmful since the heat caused by friction will bring the bearing temperature into the green zone.