Maintenance
Lubrication Interval Calculator — Grease Relubrication for Bearings
Calculate grease relubrication interval in hours for bearings in dairy plant equipment. Based on bearing bore, speed, and operating conditions.
Formula
(14000000 / (speed * Math.sqrt(bore))) * conditionFactor
bore
Bearing Bore Diameter (d) (mm)
speed
Rotational Speed (n) (rpm)
conditionFactor
Condition Multiplier
Worked Example
1
Given:
bore = 50
conditionFactor = 1
speed = 1450
2
Apply the formula:
(14000000 / (speed * Math.sqrt(bore))) * conditionFactor
3
Result:1213 hours1213 g
What is a Lubrication Interval?
The lubrication interval is the maximum number of operating hours between grease replenishments for a bearing. Too long between lubrications causes grease starvation and premature failure; too short causes over-greasing, which also damages bearings.
Formula (ISO 281 / SKF Method)
tf (hours) = (14 × 10⁶ / (n × √d)) − K
Where:
- n = rotational speed (rpm)
- d = bearing bore diameter (mm)
- K = speed factor correction (0 for n ≤ ndm/2; higher values for faster bearings)
Simplified for dairy plant bearings at moderate speed:
tf (hours) ≈ 14,000,000 / (n × √d)
Operating Condition Multipliers
| Condition | Correction Factor |
|---|---|
| Normal horizontal shaft | × 1.0 |
| Vertical shaft | × 0.5 (halve interval) |
| High temperature (> 70°C) | × 0.5 |
| Wet / washdown environment | × 0.5 |
| High vibration | × 0.5 |
| Multiple factors combined | Apply each multiplier |
In dairy plants, vertical shafts in separators, agitators in open tanks, and CIP spray environments typically need 2× more frequent lubrication.
Grease Quantity Per Lubrication
Grease amount (g) = 0.005 × d × B
Where:
- d = bearing bore (mm)
- B = bearing width (mm)
Important Notes
- Always use food-grade grease (NSF H1) for bearings in milk contact zones
- Never mix different grease types (may cause compatibility failure)
- Purge old grease properly before adding new — pump grease in slowly while bearing runs