A lubrication schedule sets out, for every lubrication point, which lubricant goes in, how much, how often, by which method and by whom. Lubrication is the maintenance task that comes round most often and goes wrong most easily: too little, too much, contaminated or simply the wrong grease. Creating a lubrication schedule means making those choices once, deliberately, and writing them down, so that everyone lubricates every point the same way. That helps reduce the risk of bearing damage, wear and unplanned downtime.
What a lubrication schedule is and why lubrication matters so much
A lubrication schedule is the part of the maintenance plan that deals with lubrication, worked out down to the level of the individual point. Where the maintenance plan says "regrease bearings every 1,000 running hours", the lubrication schedule says which bearing, which grease, how many grams, with which grease gun, and who does it.
A lubricant keeps surfaces that roll or slide over each other apart. How well it does that largely determines how long bearings, gears and chains last. It is even built into the way bearings are rated: the life calculation in ISO 281 explicitly takes the lubrication condition and contamination of the lubricant into account in the modified rating life. Grease plays the leading role: according to NLGI, the grease industry association, as many as 90 per cent of all bearings are grease-lubricated.
If a bearing fails anyway, ISO 15243 helps you interpret the damage: it describes the characteristics and possible causes of each type of bearing damage. A root cause analysis then tells you whether the lubrication schedule for that point needs to change.
Creating a lubrication schedule takes five steps:
- Identify, number and label the lubrication points.
- Choose the right lubricant for each point.
- Set quantities and intervals.
- Choose the lubrication method.
- Make sure it gets done, with rounds, notifications and clear responsibilities.
Step 1: identify and mark every lubrication point
Walk round every machine and give each lubrication point a number tied to the asset code, for example CV-03-4 for point 4 on conveyor 3. For each point, record what it is (bearing, gearbox, chain, slideway), where it is, with a photo, and how to reach it. Also record the points that deliberately get no lubrication, such as bearings that are lubricated for life or a flexible coupling, so that nobody fits a grease nipple or pumps grease into them.
Label every point with a colour and a shape per lubricant, and put exactly the same label on the grease gun, the oil can and the storage location. That way you can see at the point itself which lubricant belongs there. Combining colour with shape also works for people who have trouble telling colours apart.
Then look at access and safety. EU rules on work equipment say it must be possible to carry out maintenance with the equipment shut down, or otherwise under appropriate protective measures; in the Netherlands, article 7.5 of the Arbobesluit requires maintenance to be carried out on equipment that is switched off and depressurised or de-energised, or, where that is not possible, under effective measures. For new machinery, the manufacturer has to place maintenance points outside danger zones (Machinery Directive, Annex I, section 1.6.1). If a lubrication point sits behind a guard, run an extended line to a lubrication block outside it, or fit an automatic lubricator. If you do need to go behind the guard, stop the machine and follow the rules for safe maintenance with LMRA and LOTO.
Step 2: choose the right lubricant
First the big choice: oil or grease. Grease stays where you put it and seals the bearing against dust and moisture, which is why most bearings are grease-lubricated. Oil is the better fit where heat has to be carried away, at high speeds, and in gearboxes and hydraulics. Usually the manufacturer has already made the choice. What the specification on the pack means:
| Term | What it tells you | Example |
|---|---|---|
| ISO VG | Viscosity grade of oil at 40 °C, ±10 % | ISO VG 220: 198–242 mm²/s |
| NLGI grade | Consistency (stiffness) of grease, from 000 (very soft) to 6 (very stiff) | NLGI 2: penetration 265–295 |
| Base oil viscosity | How thick the oil in the grease is | Independent of the NLGI grade |
| Thickener | What binds the oil into a grease | Lithium complex, polyurea |
| EP | Additives for higher load-carrying capacity | Grease for heavily loaded bearings |
For oil, the viscosity grade under ISO 3448 is the key figure: the number after VG is the kinematic viscosity in mm²/s at 40 °C, with a 10 per cent margin either side. At operating temperature, oil is usually much thinner, so always compare viscosities at the same temperature: if a bearing needs a certain viscosity at 70 °C, choose a grade whose viscosity at 40 °C is considerably higher. For grease, the NLGI grade indicates consistency, or stiffness, measured as how far a cone sinks into the grease at 25 °C. That grade says nothing about the viscosity of the base oil in the grease, which matters just as much for the bearing.
Do not mix greases casually. The thickeners, base oils and additives of different greases can be incompatible: the mixture can, for example, soften too much, so the bearing runs hotter. According to NLGI, the best practice is never to mix greases, and compatibility charts are a rough guide at best. If you have to switch products, have the greases tested for compatibility.
So keep the number of lubricants down to what you really need. Fewer products mean less chance of a mix-up, less stock and simpler labels. Just do not consolidate at the expense of a specific requirement, such as an electric motor for which the manufacturer specifies a particular grease.
Storing and handling lubricants cleanly
A lubricant is only as clean as the way you store it. NLGI gives some practical rules for grease: keep containers indoors, out of the sun and away from heat sources, store drums upright and never on their side, wipe the lid clean before opening, and smooth the surface after use before closing the container again. Follow the shelf life the manufacturer states, counted from the production date on the label, and use the oldest stock first. Release the spring pressure on a grease gun you put away, or oil may separate from the grease.
Give every grease gun one type of grease and the same label as the points it is meant for. Wipe the grease nipple clean before and after greasing and fit a cap. Top up oil from a closed, labelled can, not an open bucket. A fixed, labelled place for lubricants in the stores reduces the chance of someone grabbing the wrong tin; see warehouse location codes.
Step 3: set quantities and intervals
Start with the manufacturer. The machine manual often states the lubricant, quantity and interval, and motors with regreasable bearings often carry a plate giving the grease type, quantity and interval. Those figures take precedence. Where they are missing, a widely used rule of thumb from bearing manufacturers' catalogues gives a starting value for the quantity per regreasing:
Grease quantity in grams = 0.005 × D × B
Here D is the outside diameter and B the width of the bearing, both in millimetres. The rule applies to relubrication from the side of the bearing; if the grease is fed through the lubrication groove and holes in the outer ring, bearing manufacturers work with 0.002 × D × B. For a bearing with an outside diameter of 140 mm and a width of 33 mm, that is 0.005 × 140 × 33 ≈ 23 g. Weigh once how many grams a single stroke of your grease gun delivers, because it varies from gun to gun, and put the number of strokes in the schedule.
The interval depends on speed and bearing size, temperature, contamination, moisture and vibration. As a rule of thumb, bearing manufacturers halve the relubrication interval for every 15 °C that a bearing runs above 70 °C. Dust and water call for a shorter interval: small, frequent shots push dirt out before it gets into the bearing.
Too much grease is as harmful as too little. An overfilled bearing churns the grease: friction rises, the bearing heats up and the grease ages faster. If the bearing temperature stays high after greasing, too much grease may be the cause.
Where operating time varies, set the interval in running hours rather than on the calendar. A conveyor that runs 120 hours in a busy week and 40 in a quiet one gets too little grease one time and too much the next on a fixed monthly interval. Do add a calendar limit, because grease also ages while the machine stands still. Recording running hours is covered in running-hours monitoring with IoT sensors; how they can come in automatically is shown under running hours and monitoring.
Step 4: choose the lubrication method
| Method | Suits | Watch out for |
|---|---|---|
| Manual, grease gun | Few points, easy to reach | Dose depends on the person |
| Single-point lubricator | Isolated, hard-to-reach points | Correct period setting, check it works |
| Centralised system | Many points close together | Blocked or broken lines go unnoticed |
| Oil bath or circulation | Gearboxes, large bearings | Level, leaks and oil condition |
Manual greasing has an advantage that is easily overlooked: the technician walks past and sees, hears and feels how the machine is doing. If you automate lubrication, schedule that inspection separately. A single-point lubricator dispenses a small amount continuously over a set period; check on every round that it is still working and when it will run empty.
For oil, you choose between changing it at a fixed interval and changing it on condition. Oil analysis measures viscosity, water, wear metals and contamination, among other things, so that you only change the oil when it needs changing; lubrication then becomes a form of condition-based maintenance. Contamination by solid particles is expressed in the ISO 4406 cleanliness code: three code numbers, such as 18/16/13, each standing for a range in the number of particles per millilitre of 4, 6 and 14 micrometres and larger. Each step up in a code number means roughly twice as many particles. Grease can be analysed too, for example for water and wear metals.
Step 5: make it stick with rounds, notifications and clear roles
A lubrication schedule only works if it is carried out and you can see that it has been. Set the lubrication tasks up as rounds in your maintenance system, by route and by lubricant, so that a technician with one grease gun can work along a series of points. Record for every round whether it was done or skipped, and what was noticed.
Ask for observations on every round as well: leaks, a hot or noisy bearing, milky or blackened grease, a missing cap or label. Milky grease points to water. A burnt smell at a bearing points to overheating; in that case NLGI advises shutting the machine down and checking the bearing. Deviations go into the work order process as a notification, not into a notebook.
Agree who does what. In TPM, basic lubrication is part of autonomous maintenance by operators: they lubricate the simple points to a fixed standard. Technicians take the motor bearings, the oil changes and the points that need isolation. Record this per point in the schedule, so that no point gets greased twice or not at all. Review the results as well: does grease consumption match the schedule, and how often do bearings still fail?
Example: a lubrication schedule for a conveyor drive
Take the drive of a belt conveyor at a bulk handling terminal, with varying operating hours: an electric motor, a flexible coupling, a gearbox and a drive pulley with two plummer blocks. The diagram below shows the five lubrication points; colour and shape identify the lubricant.
| Lubrication point | Lubricant | Quantity | Interval |
|---|---|---|---|
| 1 Motor bearing, drive end | Grease B, motor grease NLGI 2 | 20 g | 4,000 running hours or 1 year |
| 2 Motor bearing, non-drive end | Grease B, motor grease NLGI 2 | 12 g | 4,000 running hours or 1 year |
| 3 Gearbox | Oil C, ISO VG 220 | 12 litres | Level weekly; change after 10,000 running hours or 2 years |
| 4 Pulley bearing, drive side | Grease A, bearing grease NLGI 2 EP | 23 g | 1,000 running hours or 3 months |
| 5 Pulley bearing, free side | Grease A, bearing grease NLGI 2 EP | 23 g | 1,000 running hours or 3 months |
The motor has its own grease and its own quantities, taken from the plate on the motor. That puts two greases in this schedule, which is exactly why the colour code is needed: grease A has a lithium complex thickener and grease B a polyurea thickener, and neither belongs in the other's bearings. The pulley bearings are relubricated from the side, so the quantity follows from the rule of thumb: 140 mm outside diameter, 33 mm wide, 23 g. The coupling is a flexible type and gets no lubrication; its rubber element is covered by the inspection round. The intervals are in running hours because the conveyor runs three times as long in a busy week as in a quiet one, with a calendar limit as a safety net. All values are examples: for your own installation, use the manufacturer's data.
Common mistakes in a lubrication schedule
- Mixing greases. One grease gun for everything, or topping up with whatever happens to be on the shelf.
- Too much grease. More is not better: an overfilled bearing runs hot.
- Pumping in dirt. A dirty grease nipple or an open tin of grease puts dirt exactly where it does damage.
- A calendar interval for variable use. The interval should follow usage, not the month.
- Unclear responsibilities. The operator and the technician both assume the other one does it.
- Fitting lubricators and forgetting them. An empty or blocked automatic lubricator gives no signal of its own; include it in the round.
Frequently asked questions
What is the difference between a lubrication schedule and a lubrication chart?
A lubrication chart is usually the manufacturer's overview for one machine: a drawing or table showing the lubrication points, the lubricant and the interval. A lubrication schedule is your own version for the whole installation or plant, covering every point on every machine, with quantities in strokes, routes, who does what, labels and the link to stock. The manufacturer's chart is therefore one of the sources for your schedule.
Can you grease a machine while it is running?
Only if you cannot get near moving parts while doing it. The rules on work equipment assume maintenance on a machine that is stopped and de-energised, unless you take other effective measures. Some manufacturers actually specify relubricating a bearing while it runs, so that the grease spreads and the excess can escape through the grease outlet. That can be done safely with a lubrication point outside the guard, through an extended line or a lubrication block, or with automatic lubrication.
What should you do if you don't know which grease is in a bearing?
Purge the old grease out with the new one. NLGI advises greasing with the replacement product until more than 90 per cent of the old grease has been displaced, then watching the bearing for signs of incompatibility, such as grease softening too much or the bearing running hotter than usual, and temporarily shortening the relubrication interval. Afterwards, record which grease is in it and label the point.
How long does grease keep in storage?
It varies by product: follow the shelf life the manufacturer states, counted from the production date on the label. Poor storage shortens it. Heat and sunlight speed up oil separation, and drums kept outdoors can draw in dirt and water. If there is oil on top of the grease or dirt in the tin, ask the supplier whether it can still be used. Never reuse grease that has already been in a machine.
What does EP mean in grease?
EP stands for extreme pressure: the grease contains additives that increase its load-carrying capacity. It is meant for heavy loads, shock loads, high loads combined with higher speeds, and vibration, as found in construction and mining machinery and heavily loaded industrial equipment. Whether a bearing needs an EP grease depends on the load; here too, follow the specification of the machine or bearing manufacturer.