Bearing regreasing interval calculator
Indicative interval and grease quantity per point, corrected for temperature, contamination and vibration. The manufacturer’s recommendation always takes precedence.
Indicative method. The bearing manufacturer’s recommendation always takes precedence over this result. This tool is for ranking priorities and understanding what governs an interval — not for writing a lubrication schedule.
What this tool is for
A lubrication schedule is rarely built from a calculation. It is built from habit, often inherited, sometimes from a single interval applied to every point because one had to be chosen. This calculator does not replace the manufacturer’s recommendation — it shows the spread between points currently treated identically, and names the factor driving that spread.
The limiting factor shown with the result is the useful part. An interval divided by eight, without knowing which of the four factors did it, is a number you absorb. Knowing it is contamination is a maintenance action: improving sealing then pays more than regreasing more often.
Formula used
t = k × [ 14×10⁶ / (n × √d) − 4d ] × fT × fenv
The first term falls with speed: the faster the bearing turns, the more the grease is worked. The −4d term penalises large diameters, where peripheral speed and the quantity of grease in play both rise. The factor k depends on the bearing type.
The temperature factor is 1 up to 70 °C, then halves the interval every 15 °C — the shop-floor approximation of base oil oxidation, which follows an Arrhenius-type law. The environment factor is the product of the vertical shaft, contamination and vibration corrections.
Gp = 0,005 × D × B
Regreasing quantity in grams, from outside diameter and width in millimetres.
Variables
- Bearing type
- A ball bearing tolerates a longer interval than a roller bearing: contact is a point rather than a line, so grease is worked less. The factor applied comes from the manufacturer’s catalogue.
- Bore diameter d
- The inner diameter, read from the designation. It is the only dimension entering the interval calculation — the other two serve the grease quantity.
- Speed n
- Actual operating speed, not the nameplate maximum. On a variable frequency drive, use the most frequent speed and check the fastest operating point separately.
- Bearing temperature
- Measured at the housing, never ambient. The gap between the two commonly reaches 20 to 30 °C, and the interval halves every 15 °C above 70 °C — using the wrong measurement point skews the result by a factor of 2 to 4.
- Contamination
- Dust, splashing, high-pressure washdown. In a mining environment this is almost always the harshest factor, and the only one where a sealing improvement pays lastingly.
- Vibration and shock
- They work grease out of the raceway. A crusher or a screen falls in the severe category.
- Vertical shaft
- Grease escapes by gravity, and the lower bearing receives what the upper one loses. The interval halves.
Method and source
No ISO or ASTM standard sets a regreasing interval. The method reproduced here is the one published in bearing manufacturers’ general catalogues, where it is presented as guidance for non-monitored points — never as a prescription.
Safety
Two reservations. The calculation assumes a lightly loaded bearing (C/P ≥ 15): on a heavily loaded one it overestimates the interval. And the bearing type factors remain to be confirmed against the selected manufacturer’s catalogue. Use this page to compare points against each other and understand what governs an interval — not to set a period.
Limits of use
- This assumes a lightly loaded bearing. The reference method is a chart read from both the speed factor and the load ratio C/P, calibrated for C/P ≥ 15. The closed formula used here carries that assumption silently. On a heavily loaded bearing, grease life is shorter and this tool overestimates the interval — the dangerous direction. Where load is significant, use the manufacturer’s chart.
- The manufacturer’s recommendation always takes precedence. This tool applies a general method; the manufacturer knows the internal geometry, the cage and the sealing of their bearing. Where the two differ, theirs applies.
- The calculation assumes a standard-performance lithium soap grease on a mineral oil base. A synthetic, lithium complex or polyurea grease behaves differently, often favourably — but that difference is read on the grease data sheet, not here.
- It says nothing about grease selection: NLGI consistency, base oil viscosity, extreme-pressure additives. A correct interval with the wrong grease does not protect the bearing.
- The quantity given is a regreasing quantity, not an initial fill. Filling a new bearing and its housing follows different rules.
- Over-greasing is a failure mode in its own right: excess grease is churned, temperature rises, the base oil ages faster. Greasing "until it comes out" typically injects several times the calculated quantity.
- On instrumented equipment, vibration analysis and thermography override any calendar: they measure actual condition rather than a theoretical period. This tool is for the points that are not monitored.
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Maintenance Blueprint, « Bearing regreasing interval calculator », maintenanceblueprint.com/en/tools/regreasing-interval/