Single-Point Automatic Lubricators
When an automatic greaser is worth fitting, how to size it, and the five ways they fail · from the people who run the lubrication programme
What it is
One unit, one greasing point. It pushes a measured amount of grease in over a set period, instead of a fitter arriving with a gun on a monthly round.
Three drive types
Spring, gas and motor-driven. The choice is decided by heat, by back pressure, and by whether the interval will ever be changed — not by price.
What we do
Send the bearing list and we size the points and say which ones are worth automating — written, no charge, no commitment. We supply the grease that goes in them.
What to send us
Machine, bearing designation, speed, ambient and duty for each point. If the honest answer for a point is a fitter and a written quantity, the assessment will say so.
Which type suits your point?
Three questions. The reasoning behind each answer is in the table underneath, which is the same table either way — this only saves you reading it three times.
1. How many points like this one?
2. The ambient at the point
3. Will someone review the setting at three months?
Motor-driven
You are going to change the setting, so buy the drive that lets you: the rate is a dial on the unit. A gas unit means swapping the activator cell to change anything; a spring unit is fixed once fitted.
Spring-driven
A couple of points, steady conditions, and nobody coming back to it. That is exactly where a low-cost disposable unit earns its place — there is nothing to adjust and nothing to forget.
Motor-driven
The ambient swings, so rule out gas: the drive is a chemical reaction and the real dispense period drifts with temperature. A motor turns at the same rate whatever the ambient.
Spring-driven
Not gas — a swinging ambient makes a chemical drive wander, and nobody is reviewing it. A spring unit is slowed by cold grease but has no chemistry to drift.
Motor-driven
At a dozen points you will want to change settings after the first review, and doing that on a gas unit means a cell per point. A dial is a dial.
Gas / electrochemical
Moderate point counts in stable conditions, set once: this is where a gas unit earns its place. Choose the activator cell at installation and leave it.
Motor-driven
Temperature independence is the deciding factor at this point count, and it is the one thing a gas unit cannot give you.
Motor-driven
A swinging ambient with no review is the worst case for a drift-prone drive. Pay once for a motor unit that holds its rate, because nothing downstream is going to catch the drift.
Mounting the unit away from the point, on a length of tube? Then motor-driven whatever the answers above — it is the only drive with the 5–10 bar to push grease down a feed line.
Mounted on the point, the drive only has to push into the bearing. On a feed line it has to push the length of the tube as well, which is the whole of the back-pressure row in the table below.
Three drive types, and they are not interchangeable
Single-point lubricators all do the same job — push a measured amount of grease into one point over a set period. What separates them is how the piston is driven, and that decides everything about where each one belongs.
Swipe the table sideways to see every column.
| Compared on | Spring-driven | Gas / electrochemical | Motor-driven |
|---|---|---|---|
| How it drives the piston | A wound spring pushes a plunger. | An electrochemical cell generates gas; the gas pressure drives the piston. | A battery-powered motor and gearbox drive the piston. |
| How the rate is set | Largely fixed by the spring and the grease. Little adjustment once fitted. | By the activator cell you choose at installation. Changing the rate means changing the cell. | By a switch or dial on the unit, changed at any time without opening the grease side. |
| Temperature sensitivity | Low, but grease stiffness at low temperature slows delivery. | High. Gas generation is a chemical reaction — it speeds up in heat and slows in cold, so the real dispense period drifts from the nominal one. | Low. The motor turns at the same rate whatever the ambient, within the unit’s rated range. |
| Working against back pressure | Weakest. Not for long feed lines or a stiff bearing. | Moderate, limited by the gas pressure the cell can raise. | Strongest — typically 5 to 10 bar, enough for a remote-mounted unit on a feed line. |
| Refill or replace | Usually a disposable unit. | Usually a disposable unit, or a replaceable cell and cartridge. | Drive unit is reused for years; you replace the grease cartridge and the battery. |
| Typical dispense period | Weeks to a few months. | 1 to 12 months, set by the cell. | 1 to 12 months, set on the unit. |
| Where it earns its place | Single low-cost points, short runs, where nobody will come back to adjust it. | Moderate point counts in stable ambient conditions, where the setting will not need changing. | Anything where the interval must be changed after the first review, where the ambient swings, or where the point is remote or hazardous. |
Sealing and certification vary by unit rather than by drive type: IP65 bodies and hazardous-location certification are both available. If the point is in a classified zone, the certificate on the specific unit is what matters, not the category.
Sizing: the number you are choosing is grease per day, not months
A dispense period of “six months” sounds like a maintenance interval. It is not. It is a rate — the reservoir divided by the period. A 150 ml unit set to six months is delivering under a millilitre a day; the same unit set to one month is delivering five. Sizing is deciding the daily rate the bearing wants and then picking a reservoir and period that give it.
The same unit, four settings. Choosing a period is choosing the second number, not the first.
Start from the bearing maker’s relubrication quantity and interval for that bearing at that speed, then adjust for what the plant actually does to it: shaft speed relative to the rating, operating temperature, vertical shafts (which lose grease faster), contamination and washdown, and continuous versus intermittent running. The output is a millilitres-per-day figure. Everything after that is arithmetic.
Then review it. The first setting is an estimate. Three months in, the evidence is on the bearing — temperature, purge at the seal, grease condition and colour. That review is what separates a lubrication programme from a box screwed onto a grease nipple.
Work out the daily grease rate for a bearing
The sizing method above, as something you can put numbers into. Bearing dimensions and running conditions in, millilitres per day out, and what that means on each reservoir size. The arithmetic runs in your browser — nothing is sent anywhere.
The bearing maker’s figure always wins. Enter it and the estimate is ignored.
How this is worked out
Relubrication quantity Gp = 0.005 × D × B grams, the standard rolling-bearing figure, converted to millilitres at 0.9 g/ml for an NLGI 2 soap-thickened grease.
The interval starts from the speed factor A = n × dm, where dm is the mean diameter (d + D) / 2, read off the ball-bearing band and then multiplied by a bearing-type factor — 1 for ball, 0.5 for cylindrical roller, 0.25 for spherical and taper. It is then corrected: halved for every 15 °C above 70 °C, halved again for a vertical shaft, and cut to a half or a quarter for a dusty or wet environment. These are the standard correction factors published by the bearing makers.
Daily rate is the quantity divided by the corrected interval expressed in days at your running hours. The period for each reservoir is the reservoir divided by the daily rate.
This is a starting point, not an answer. It cannot see your grease, your seal condition, your feed line or your duty cycle. Set the unit, then review the bearing at three months — temperature, purge at the seal, and the condition of the grease coming out — and correct the setting from what you find.
Which points are worth automating
Not every greasing point earns a unit. The ones that do share four things, and a point with none of them is better left on the route.
- Hard to reach, or reached only with a permit. At height, behind a guard, inside a classified zone, or on a machine that has to stop first. The cost of greasing it is the access, not the grease.
- It keeps getting missed. If the lubrication chart says monthly and the bearing says otherwise, the point is telling you the route does not reach it.
- It wants small, frequent doses. A bearing that needs a few millilitres a week is badly served by a full gun every quarter — the seal sees a pressure spike, then months of nothing.
- The failure is expensive. Not the bearing — the bearing is cheap. The kiln run, the season, the crane that blocks a berth.
Swipe the table sideways to see every column.
| Plant | The points that keep getting missed | Why it bites |
|---|---|---|
| Cement | ID and FD fan bearings, mill and separator fans, bucket-elevator head shafts, crusher rotor bearings, belt-conveyor pulleys | Hot, dusty and continuous. A missed point becomes a bearing change in the middle of a kiln run. |
| Steel and rolling | Roller-table bearings, EOT crane travel wheels and hoist blocks, dust-collector and exhaust fans, descaling pumps | Radiant heat thins the grease, and most of these are reachable only in a shutdown. |
| Sugar | Mill roller journals, juice and injection pumps, bagasse and cane carriers, centrifugal drives | The season runs flat out. Nothing comes off line to be greased, so the route quietly shortens. |
| Power and thermal | Cooling-tower fan and gearbox bearings, ID fans, coal-handling conveyors, boiler feed and circulation pumps | At height and in the wet. Water washes grease out faster than any calendar allows for. |
| Ports and bulk handling | Crane travel and slew bearings, conveyor idlers, stacker-reclaimer drives, hopper vibrators | Spread over hundreds of metres. A full greasing route is a shift’s work for one person. |
| Pharma and food | Bottle washers, fillers and cappers, mixers and grinders, exhaust and air-handling fans | Washdown drives grease out of the seal, and over-greasing by hand puts it where product runs. |
| Textile | Dyeing-machine and stenter bearings, blowers, humidification-plant fans, sandblasting and finishing drives | Fine lint packs the housing. A hand shot pushes it in rather than purging it. |
| Chemical and refinery | Circulation and sewage pumps, agitator and extruder drives, blowers, waste-gas valve actuators | A grease gun in a classified zone is a work permit. The unit removes the permit, not just the walk. |
| Mining and quarry | Screen and vibrator bearings, crusher and apron-feeder drives, long-belt idlers, dewatering pumps | Shock load plus abrasive dust. These are the points that most reward a small continuous feed. |
| General engineering | Extraction and dust-collector fans, air compressors, saw and grinder spindles, heat-treatment and forming machines | Small bearings nobody owns. They fail quietly and take a machine with them. |
And what not to automate
A point on a route that is genuinely walked, and where the bearing shows it. A bearing that needs a flush and a fresh charge rather than a trickle — a unit will not clean out degraded grease, it will only add to it. Anything where the consequence of failure is a cheap bearing and an hour. And any point where nobody will do the three-month review, because an unreviewed unit is a guess that has been automated.
A lubricator does not replace the route. It removes from the route the points the route keeps missing, so the time you have goes to the ones that need a person looking at them.
Five ways they fail, all of them avoidable
Each one is a decision somebody did not come back to. Open any of them.
Set once, never reviewed
The dispense period is chosen on the day of installation from an OEM figure, and then nobody goes back to it. Duty changes, ambient changes, the bearing beds in — and the setting does not. A lubricator on the wrong setting is a more reliable way of over-greasing a bearing than a grease gun is.
Nobody notices when it stops
A blocked feed line, an exhausted battery or a spent cell produces no noise and no alarm on most installations. The bearing runs dry for months while the plant believes it is on an automatic programme. Units with a blockage indicator help; a route that physically checks the dispensed level helps more.
Grease incompatibility on the refill
A lithium-complex unit topped up with a calcium sulphonate grease, or a polyurea motor grease crossed with lithium, can thicken, soften or separate in the cup. The failure looks like a lubricator fault and is a grease-selection fault. Keep one soap type per point and record it.
Remote mounting beyond the unit’s pressure
Mounting the unit off the machine on a length of tube is often the only way to reach a hot or guarded point — but the unit then has to push grease down that line. Spring and gas units run out of pressure quickly; a motor-driven unit rated to 5–10 bar will usually carry it. Match the drive to the line, not to the price.
Cold starts and hot rooms
Gas-driven units speed up in heat and slow in cold, because the drive is a chemical reaction. In a Telangana summer roof plant and an air-conditioned clean area, the same nominal setting will not give the same delivery. If the ambient swings, the drive type matters more than the setting does.
The problem is not that nobody greases. It is that nobody knows how much.
SKF put poor lubrication behind more than 36% of premature bearing failures. Almost none of that is neglect. It is grease going in at the wrong interval, in the wrong quantity, or of the wrong type — and the two failure modes look nothing alike.
Under-greasing is the one everyone pictures: the film thins, metal meets metal, the bearing runs hot and fails. Over-greasing is the one that surprises people, and it is more common. A packed housing has nowhere to put the excess, so the rolling elements churn it. Churning generates heat, the heat degrades the grease, the pressure pushes past the seal, and on an electric motor the escaping grease finds the windings. A bearing that was greased every week by a diligent fitter can fail sooner than one that was left alone.
The framework the lubrication trade uses for this is the five Rs: the right lubricant, in the right volume, at the right point, at the right interval, by the right method. A grease gun on a monthly round gets the point and the method right and leaves volume and interval to whoever is holding it.
What we do about it
We run the lubrication side of plants for a living, which is the part of this that automatic lubricators do not solve on their own. Our shop-floor and plant maintenance programme starts with the asset register — every machine, its lubrication points, the correct grade for each point, the volume and the interval. That register is exactly the input a lubricator sizing needs, and most plants have never had it written down in one place.
And we supply what goes in them. Lithium complex, calcium sulphonate, polyurea and synthetic greases across Veedol, Balmerol, GS Caltex Kixx and SELCO — so the soap type in the cup and the soap type in the bearing are a decision somebody made, rather than whatever was in the store.
Send us the bearing list and we will size the points. Machine, bearing designation, speed, ambient, duty. You get back a written assessment of which points are worth automating, what daily rate each one wants, and which drive type suits the position — no commitment and no charge. If the answer for a point is “a fitter with a grease gun and a written quantity”, that is what it will say.
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Related
- Shop-floor and plant maintenance — the asset register and the lubrication programme
- Oil analysis service — the same discipline applied to oil-lubricated equipment
- Manual or automatic greasing — the grams a bearing wants, and calibrating a grease gun
- Gear oil change intervals — why calendar-based intervals mislead
- Industrial lubricants and greases — the range we stock in Secunderabad