1. Scope and purpose
This manual covers lubrication analysis and relubrication scheduling procedures for industrial rolling and plain bearings in critical manufacturing equipment. The goal is to ensure the reliable operation of the bearings, extend their service life and prevent unplanned production stops by choosing the right lubricant, determining the optimal relubrication intervals and monitoring the condition of the lubricant. Compliance with these recommendations is mandatory for equipment operating in the automotive, aerospace, food, chemical and energy industries.
2. Precautions
WARNING: Before beginning any maintenance work, ensure that the equipment is completely shut down, de-energized and locked out in accordance with your facility's LOCKOUT/TAG OUT (LOTO) procedures. This prevents accidental start-up and protects personnel from moving parts, electric current and other dangerous energy sources.
WARNING: Hot surfaces: Bearings and surrounding components may be hot during or after operation. Use heat-resistant gloves and other appropriate PPE.
WARNING: Lubricants can cause skin and eye irritation. Use safety glasses, nitrile or chemical resistant gloves. In case of contact with skin or eyes, rinse immediately with plenty of water and seek medical attention.
Mandatory PPE: Safety glasses, nitrile gloves, work clothes, safety shoes.
3. Necessary tools and materials
| Tool / Material | Specification | Quantity |
|---|---|---|
| Lubricant syringe | Manual or pneumatic, with a calibrated dispenser (±5 g) | 1 |
| Infrared thermometer | Measuring range from -30°C to +400°C, accuracy ±1.5°C | 1 |
| Contact thermometer | Probe for surface measurements, range from 0°C to +250°C | 1 |
| Tachometer | Laser or contact, range up to 20,000 rpm, accuracy ±0.05% | 1 |
| Lubricant sampling kit | Vacuum pump, sterile sample bottles (50-100 ml) | 1 |
| Cleaning kit | Lint-free wipes, degreaser (for example, isopropyl alcohol) | 1 |
| Lubricant (appropriate type) | According to the manufacturer's recommendations or after analysis | Depends on the volume |
| Lubricant compatibility charts | Printed or digital (e.g. from UNITEC-D or OEM) | 1 |
| Torque wrench | Range 5-50 Nm, for grease nipples and covers | 1 |
| A set of keys and sockets | Metric, for access to lubrication points | 1 |
4. Pre-service checklist
| Item | Verification | Acceptance/rejection criteria | Notes |
|---|---|---|---|
| 1. Service history | Get acquainted with the date of the last relubrication, type of lubricant, volume. | Availability of complete documentation. | If there are no data, consider the type of lubricant unknown. |
| 2. Visual inspection of the bearing assembly | Check for oil leaks, seal damage, corrosion, and foreign objects. | No leaks, integrity of seals, no visible damage. | Leaks may indicate excessive relubrication or damaged seals. |
| 3. Lubricating nipples | Check the cleanliness and integrity of the grease nipples. | The nipples are clean, not clogged, not damaged. | Dirty nipples can lead to contamination of fresh lubricant. |
| 4. Bearing temperature (during operation) | Measure the temperature of the bearing housing with an infrared thermometer. | Temperature within normal limits (typically <70°C or as per OEM). | Elevated temperature may indicate problems with the lubricant or bearing. |
| 5. Rotation speed | Measure or obtain data on the speed of rotation of the shaft. | Corresponds to design or working speed. | Required to calculate the speed factor (DN). |
| 6. Type of equipment and bearing | Identify the type of machine and bearing (model number). | Accurate identification. | It affects the choice of lubricant and relubrication intervals. |
5. Step-by-step procedure
5.1. Collection of data on bearing operation
- Measure the operating temperature of the bearing:
- Use an infrared thermometer for a quick non-contact measurement of the surface of the bearing housing. Also use a contact thermometer to more accurately measure the temperature on the outer race or bearing housing.
- Record the maximum stable temperature during normal operation.
- Common mistake: Measuring temperature immediately after starting or stopping, which gives inaccurate data. Wait for the temperature to stabilize.
- Determine the speed of rotation of the shaft (rpm):
- Use a tachometer (laser or contact) to measure the speed of the shaft.
- If the equipment has a CNC or PLC, check the speed reading on the control panel.
- Record the rated operating speed.
- Common mistake: Assuming speed instead of measuring, especially for variable speed equipment.
- Collect bearing information:
- Record the inner diameter (d, mm), outer diameter (D, mm) and width (B, mm) of the bearing. This information can be found in the OEM documentation or on the bearing itself.
- Determine the type of bearing (e.g. ball, roller, taper).
- Evaluate loading and environmental conditions:
- Determine whether the bearing is exposed to high shock loads, vibration, extreme temperatures, exposure to water, dust, or aggressive chemicals.
- These factors significantly affect the choice of lubricant and the relubrication interval.
5.2. Calculation of speed factor (DN) and relubrication interval
- Calculate the speed factor (DN):
- DN = D (bearing outer diameter in mm) × n (speed of rotation in rpm).
- This factor is critical for lubricant selection and interval determination.
- Example: For a bearing with D=100 mm rotating at a speed of 1500 rpm, DN = 100 * 1500 = 150,000.
- Determine the initial relubrication interval:
- Use the bearing manufacturer's recommendations (eg SKF, FAG) or the OEM documentation. These are usually graphs or formulas that take into account the DN factor, bearing type and operating conditions.
- For general cases, you can use empirical formulas. For example, for cylindrical roller bearings, the interval can be smaller than for ball bearings at the same DN.
- Adjust the relubrication interval by temperature:
- According to the Arrhenius rule, every 10-15°C increase in the operating temperature of the bearing above 70°C cuts the grease life in half.
- Use correction factors (fT) according to standards (eg ISO/TR 10609) or lubricant manufacturers' recommendations.
- Example: If the base interval is 1000 hours at 70°C, then at 80°C it will be 500 hours, and at 90°C it will be 250 hours.
- Adjust the interval for other factors:
- Load (fP): high loads shorten the interval.
- Vibration (fV): Strong vibration shortens the interval.
- Pollution (fE): Dust, moisture, chemicals shorten the interval.
- Common mistake: Applying a single interval for all bearings without taking into account individual conditions.
5.3. Analysis of lubricant samples (if necessary)
- Lube Sampling:
- SAFETY: Make sure the sampling source is safe and not under pressure. Use appropriate PPE.
- Select a representative sampling point (eg drain hole, grease nipple during operation if safe to do so).
- Clean the area around the sampling point to avoid external contamination.
- Use a clean, dry vacuum pump and sterile sample bottles (50-100 ml).
- Take a sample of grease that is representative of the operating condition of the bearing.
- Common error: Sampling from an unrepresentative point (for example, from a tank where the oil does not circulate) or contamination of the sample during sampling.
- Visual inspection of the sample:
- Check for color, clarity, presence of solids, water, or change in consistency (solidification/liquefaction).
- A sudden change in color or the presence of particles may indicate degradation of the lubricant or wear of the bearing.
- Laboratory analysis (recommended):
- Send samples to an accredited laboratory for comprehensive analysis:
- Spectroscopy: Determination of the concentration of wear metals (Fe, Cr, Ni, Cu, Pb, Sn - from bearings, Ca, Li, Al - from grease), impurities (Si - dust).
- IR-spectroscopy (FTIR): Determination of oxidation, nitration, presence of water, changes in base lubricant.
- Viscosity: Kinematic viscosity measurements at 40°C and 100°C.
- Moisture: Karl Fischer's method (ISO 12937) for accurate determination of water content.
- NLGI Consistency: Penetration measurement (ISO 2137) to evaluate consistency.
- Ferrography: Analysis of the morphology of wear particles to determine the type of wear.
- Common mistake: Ignoring laboratory recommendations or lack of regular analysis for critical equipment.
5.4. Determination of lubricant compatibility
- Identify current and planned lubricant type:
- Find information on base oil (mineral, synthetic: PAO, ester, silicone) and thickener type (lithium, lithium complex, calcium, polyurea, aluminum complex). This information is contained in the technical data sheets of lubricants (SDS/TDS).
- Check compatibility with tables:
- Use standard lubricant compatibility tables provided by UNITEC-D, lubricant manufacturers or OEMs.
- Tables usually denote compatibility as:
