How to Size an Automatic Lubrication System: From Lubrication Points to Pump Output

Choosing an automatic lubrication pump should normally come near the end of the sizing process—not at the beginning.

Before discussing pump pressure, reservoir capacity or a specific model, we first need to understand what the machine actually requires:

• How many lubrication points are there?
• How much lubricant does each point need?
• How often must lubrication occur?
• What grease or oil will be used?
• How far must the lubricant travel?
• What is the lowest operating temperature?
• How quickly should one lubrication cycle be completed?
• How will the system confirm that lubrication has taken place?

Two machines can both have 40 lubrication points and still require very different systems.

A compact machine with closely grouped bearings is not the same design problem as a crusher, conveyor or port crane with lubrication points distributed across a large structure.

When we review a project at INA, we therefore work from the machine back toward the pump:

Lubrication points → required volume → lubrication interval → system architecture → metering → pump output → pressure and piping → reservoir → monitoring

This guide shows how to make that preliminary calculation before selecting components.

Engineering note: Final lubricant quantities and lubrication intervals should always be checked against the machine, bearing and lubricant manufacturer's requirements. The calculations below are intended for preliminary system sizing.

1. Start With a Lubrication Point Schedule

The most useful starting document is not a pump datasheet.

It is a lubrication point schedule.

For every bearing, pin, bushing, guide, gear or other lubrication point, record:

• point identification;
• physical location;
• lubricant type;
• required lubricant quantity;
• lubrication interval;
• existing manual lubrication method, if applicable;
• approximate distance from the expected divider or injector location.

For example:

The important sizing result is not simply:

24 lubrication points

It is:

5.40 cm³ required for one complete lubrication cycle.

That number can now be used to evaluate the distribution system, pump delivery and reservoir consumption.

Do not assume every lubrication point needs the same quantity

A small bearing, a large pivot and a heavily loaded pin may all be installed on the same machine but have different grease requirements.

Supplying equal quantities to every point can result in over-lubrication at some locations and insufficient lubrication at others.

The metering arrangement should therefore follow the actual requirement of each point.

2. Calculate Lubricant Demand Over Time

Once the volume required for one cycle is known, determine how often that cycle must occur.

Assume the example machine operates:

• 16 hours per day;
• 6 days per week;
• one lubrication cycle every 30 minutes.

This produces:

16 hours × 2 cycles/hour = 32 cycles/day

Daily theoretical grease demand is therefore:

5.40 cm³ × 32 = 172.8 cm³/day

Weekly demand becomes:

172.8 × 6 = 1,036.8 cm³/week

or approximately:

1.04 L/week

Now we have a useful basis for evaluating pump delivery and reservoir capacity.

Do not copy manual greasing quantities directly

When equipment is converted from manual greasing to automatic lubrication, one common mistake is to copy the manual grease quantity into every automatic lubrication event.

Suppose the maintenance schedule currently requires:

6 cm³ every eight operating hours.

An automatic system does not necessarily need to inject all 6 cm³ at once.

The same total requirement may be divided into smaller, more frequent doses, provided the final lubrication strategy remains consistent with the equipment manufacturer's requirements.

The more useful design question is therefore:

How much lubricant does this point require over time?

not:

How much grease does the technician normally apply during one manual service?

Converting grams to volume

Maintenance manuals sometimes specify grease in grams while pump and divider displacement is given in cm³.

Use:

Volume = Mass ÷ Lubricant Density

Always use the density stated on the actual lubricant technical data sheet rather than assuming that all greases have the same density.

3. Select the Lubrication System Architecture

Before final pump selection, determine how lubricant should be distributed.

Point count alone cannot determine whether the machine should use progressive, single-line or dual-line lubrication.

If this decision has not yet been made, our Progressive vs Single-Line vs Dual-Line Lubrication Systems guide explains the main differences in greater detail.

As a practical starting point:

Progressive systems are often worth evaluating when lubrication points can be grouped into manageable circuits and cycle monitoring is useful.

Single-line systems can be suitable where independent injectors and individual metering are preferred.

Dual-line systems deserve consideration when the machine is physically large, main lines are long, lubrication points are widely distributed or total grease demand is relatively high.

The important principle is this:

Do not try to correct an unsuitable system architecture simply by installing a larger pump.

4. Calculate the Pump Output Required

After determining the total lubricant demand per cycle, calculate the theoretical pump delivery required within the permitted lubrication time.

For our example:

Required lubricant per cycle = 5.40 cm³

Suppose one complete lubrication cycle should finish within:

3 minutes

The theoretical minimum average delivery is:

5.40 ÷ 3 = 1.80 cm³/min

This gives a useful starting point.

However, it does not mean that any pump with a catalog rating above 1.80 cm³/min is automatically suitable.

The selected pump must still be evaluated against:

• lubricant consistency;
• minimum temperature;
• expected operating pressure;
• pipe dimensions;
• pump element configuration;
• distributor resistance;
• actual cycle completion time.

The LUBElite Progressive Lubrication Pump can therefore be considered only after these project conditions have been defined.

How much safety margin should be added?

There is no single percentage that is correct for every lubrication system.

Rules such as “add 20%” or “choose a pump 30% larger” may be convenient, but they do not replace engineering review.

The design allowance should reflect real uncertainty, such as:

• lower operating temperature;
• variations in grease behavior;
• pipe pressure losses;
• future system expansion;
• changes in machine operating hours;
• pump wear;
• required cycle completion time.

A compact indoor machine operating at controlled temperature does not necessarily require the same allowance as mining or port equipment working outdoors through a wide temperature range.

A better method is to calculate the theoretical demand first and then identify exactly what uncertainty the additional capacity is intended to cover.

5. Check Pressure, Pipe Length and Grease Behavior

Flow and pressure need to be considered separately.

A pump can theoretically supply enough grease volume but still struggle to move that grease through the installed piping network.

A useful conceptual relationship is:

Required pressure ≈ piping resistance + metering-device resistance + lubrication-point backpressure + design allowance

Several factors can increase system resistance:

This is why lubrication tubing, hoses and fittings should be considered during system design rather than after the pump has already been selected.

Measure the installed route, not the straight-line distance

When customers send us machine drawings, one issue we regularly check is whether the stated pipe length represents the real installation route.

A lubrication point may be five meters from the pump in a straight line but require nine meters of actual hose after routing around:

• machine guards;
• moving assemblies;
• structural members;
• maintenance access;
• heat sources.

The same applies to secondary lines between dividers and lubrication points.

For preliminary sizing, use realistic installed lengths.

6. Design Around the Lowest Operating Temperature

Temperature is one of the easiest variables to underestimate.

A system commissioned at +20°C may behave very differently when the same machine starts at -15°C or -25°C.

When temperature falls, grease can become more difficult to move through long or restrictive lines.

For low-temperature projects, evaluate the combination of:

• grease specification;
• NLGI grade;
• base-oil viscosity;
• minimum operating temperature;
• pipe length;
• pipe diameter;
• pump capability;
• expected system pressure;
• required cycle time.

Do not treat maximum pump pressure as the only answer to a low-temperature problem.

If the lubricant, piping and system layout are poorly matched, simply increasing available pressure does not necessarily produce a reliable design.

For outdoor construction, mining, port and wind-power equipment, the lowest expected operating temperature should therefore be provided at the beginning of the project.

7. Size the Reservoir From Actual Consumption

Reservoir sizing becomes straightforward once daily lubricant consumption is known.

In our example:

Daily theoretical consumption = 172.8 cm³

Suppose the maintenance team would like to refill the system approximately every three operating weeks.

At six operating days per week:

172.8 × 18 = 3,110.4 cm³

or approximately:

3.11 L

A nominal reservoir only slightly larger than 3.11 L would leave very little practical reserve.

Final reservoir selection should also consider:

• usable rather than nominal capacity;
• remaining grease when the low-level alarm activates;
• refill method;
• maintenance schedule variation;
• operational reserve.

This may make the next available reservoir size more practical.

At the same time, selecting the largest reservoir available is not automatically better. Excessive reservoir capacity can increase space requirements, machine weight and lubricant inventory.

The correct reservoir should support the intended maintenance interval.

8. Match the Divider or Injector to Individual Point Demand

The pump supplies the lubrication circuit.

The distribution components determine how that lubricant is divided between points.

Return to our example:

• 8 points require 0.25 cm³;
• 12 points require 0.15 cm³;
• 4 points require 0.40 cm³.

Simply pumping 5.40 cm³ into a manifold does not guarantee that each point receives its correct amount.

In a progressive lubrication system, the divider configuration needs to reflect these required delivery ratios.

INA's PFM Progressive Lubrication Divider family provides different metering configurations and monitoring options, allowing the divider arrangement to be selected around the lubrication circuit rather than treating every application as identical.

Group lubrication points logically

A machine with 40 points concentrated around one frame is very different from a machine with 40 points spread over a long structure.

It may be more practical to organize large equipment into zones:

Pump → Main distribution → Zone A → Zone B → Zone C → Individual points

This can reduce unnecessary secondary-line length and make troubleshooting easier.

The layout should make sense both physically and hydraulically.

9. Decide How the System Will Confirm Lubrication

A pump motor running does not necessarily prove that grease has reached the intended lubrication circuit.

Depending on equipment criticality, monitoring may include:

• reservoir low-level signal;
• pump operation;
• system pressure;
• divider movement;
• lubrication-cycle completion;
• controller timeout;
• machine alarm or PLC interlock.

In progressive systems, divider movement can provide useful confirmation that the progressive sequence is operating.

The PFM range, for example, includes versions with piston detection and visual indication.

The control strategy can then be managed through an automatic lubrication system controller according to the required lubrication interval and feedback logic.

Monitoring should be defined during system design rather than added after commissioning.

10. Worked Example: Preliminary Sizing for a 24-Point Crusher

Now we can combine the calculations.

Step 1: Evaluate system architecture

The lubrication points can be grouped around the crusher and cycle confirmation is required.

Based on these preliminary conditions, a progressive lubrication system would be a logical architecture to evaluate first.

This is not yet a final recommendation because actual bearing backpressure, grease specification, pipe dimensions and machine layout still need to be confirmed.

Step 2: Determine metering

The lubrication points require three different delivery quantities:

• 0.15 cm³;
• 0.25 cm³;
• 0.40 cm³.

The divider configuration must therefore reflect these different requirements.

Step 3: Check theoretical pump delivery

Required volume:

5.40 cm³/cycle

Maximum cycle time:

3 minutes

Therefore:

5.40 ÷ 3 = 1.80 cm³/min theoretical average delivery

The selected pump must then be checked with NLGI 2 grease at -10°C through the real pipe network.

Step 4: Check reservoir requirement

Theoretical consumption over 18 operating days:

approximately 3.11 L

Reservoir selection should exceed this by enough to account for usable volume, low-level alarm position and maintenance variation.

Step 5: Define monitoring

Because cycle confirmation is required, divider-cycle detection should be considered together with low-level and controller alarm functions.

Preliminary result

Compare that with an enquiry that simply says:

“Please quote a grease pump for 24 lubrication points.”

The second set of information allows us to discuss a lubrication system rather than guess a pump.

11. Five Common Sizing Mistakes

1. Selecting the pump from point count alone

Twenty large bearings can consume more grease than 60 small points.

2. Choosing the highest-pressure pump

Maximum pressure is not the design target. High operating pressure may also indicate restrictive piping, cold grease or a blocked circuit.

3. Giving every point the same quantity

Metering should match the actual lubrication requirement of each component.

4. Ignoring temperature and installed pipe length

A system designed from room-temperature data and straight-line machine dimensions may behave differently in actual service.

5. Treating pump operation as proof of lubrication

For critical equipment, pressure, divider movement or cycle-completion monitoring may be required.

Automatic Lubrication System Sizing Data Sheet

Before requesting a preliminary system review, prepare the following information:

If the exact lubricant quantities are not yet known, send the machine lubrication manual, current maintenance schedule and a marked equipment drawing.

These are usually more useful than selecting a pump from lubrication-point count alone.

FAQ

How do I calculate automatic lubrication pump output?

Calculate the total lubricant required for one complete cycle and divide it by the maximum acceptable cycle time.

For example:

6 cm³ ÷ 3 min = 2 cm³/min theoretical average delivery

Then verify the pump under the actual lubricant, temperature, pressure and piping conditions.

How much larger should the pump be than calculated demand?

There is no universal percentage.

The allowance should cover identified uncertainties such as low-temperature grease behavior, pressure loss, operating variation, future expansion and required cycle time.

Can I size the system only from the number of lubrication points?

No.

You also need lubricant quantity, interval, point location, piping distance, lubricant specification, operating temperature and monitoring requirements.

Does higher pump pressure allow longer grease lines?

Not automatically.

Line length must be evaluated together with internal diameter, lubricant behavior, temperature, fittings and system backpressure.

How should I choose the reservoir size?

Calculate lubricant consumption over the desired refill interval first, then allow for usable capacity, low-level alarm position and operational reserve.

What should I send INA for preliminary system selection?

Provide the machine type, lubrication-point layout, lubricant specification, required quantity, lubrication interval, operating hours, temperature range, pipe distances, available power and monitoring requirements.

Size the Lubrication Circuit Before Choosing the Pump

When we review an automatic lubrication project, the useful starting question is rarely:

“Which pump is large enough?”

A better question is:

“What does this machine require at each lubrication point, and under what conditions must that lubricant be delivered?”

Once the lubrication-point schedule, cycle demand, piping distances, temperature and monitoring requirements are known, pump and divider selection becomes much more straightforward.

For preliminary project review, send INA your machine layout, lubrication-point schedule, lubricant specification, operating temperature, cycle requirement, piping distances and monitoring requirements.

We can then evaluate the appropriate system architecture and component combination around the actual machine requirements instead of selecting equipment from point count alone.