Mining Tire Foam Filling Process Step by Step

In modern mining, tire failure accounts for one of the costliest forms of downtime. A single flat on a wheel loader, underground LHD, telehandler or other mining support vehicle can halt production, cripple haul cycles, and ruin budgets in an instant.

For this reason, more mining contractors are moving away from pneumatic tires towards polyurethane foam filled tires. Unlike air-filled tires, foam filled tires don’t go flat, don’t puncture beside of the tire, lose air via blown beads, and don’t suffer from many other kinds of catastrophic tire failure.

Foam filling is not a magic bullet, however, and its effectiveness depends very heavily on the filling process. Inadequate filling procedures create voids inside the tire, stress parts of the tire and are likely to cause premature sidewall cracking, excessive heating of the tire, and potential damage to the wheel.

Drawing from field experience of similar projects in Asia, Africa, Australia and South America, this guide explains the complete mining tire foam filling process as used by professional tire service centres and industrial foam filling plants in 2026.

Why Process Control Matters More Than Foam Density

Many inexperienced buyers latch onto foam density specs like a drowning man.

This is the wrong starting point.

A tire filled with the best polyurethane will perform poorly if the sequence of filling, management of pressure, and patterns of curing are wrong.

A properly filled tire with a medium-density formulation will, in fact, often run longer into its life if filling is doneproperly, because of even separation of pressure internally.

An experienced operator will place far less faith in the density number of the foam than in the filling process itself.

Step 1. Tire Inspection and Suitability Assessment

Before filling commences, the technician must examine the tire and determine if it is suitable for foam filling.

Checklist for Inspection

• Tire carcass condition
• Sidewall integrity
• Bead area damage
• Existing punctures
• Condition of internal liner
• Condition of rim
• Corrosion level of the wheel

Typical conditions for rejecting tires, prior to commencing filling, include:

Severe Sidewall Separation

Sidewall separations that are large enough to continue growing after filling will cause the filled tire to slowly and permanently deform into this “flat” condition.

Exposed Cord Damage

When steel cords are exposed, they form an obvious structural weakness and are 100% likely to rapture if the foam fill process is attempted.

Excessive Heat History

Undisclosed thermal damage factor.

If the tire has previously been operated on some service that has overheated it, it may have suffered undocumented thermal damage to the carcass structure that cannot be rehabilitated by foam filling or other means.

Foam filling does not fix tire structure.

The filled tire acts no different than that of a tire filled with air.

Step 2. Tire Preparation

The tire must then be mounted on the rim and properly set-up for filling at the filling station.

The preparation procedure then generally goes as follows:

1. Clean area about valve.
2. Remove moisture.
3. Remove any contaminant that may hinder polyurethane chemistry.
4. Verify integrity of wheel.
5. Install filling valve system.

Moisture trapped inside the tire can and often does adversely impact the chemical reaction of the two components of polyurethane.

This is particularly critical in mines that are in humid areas.

Most filling stations are now equipped with high-volume air drying systems.

In any case, the water is driven out before injection begins.

Step 3. Selecting Foam Density

Different mining activities result in different requirements for foam density.

Typical Range of Densities is Generally

Higher density does not automatically denote superior performance.

A common approach is the maximization of density as previously described.

This maximization of density results in a proportionate increase in:

• Weight of tire
• Fuel burn
• Strain on vehicle drive components
• Heat generated by the fill material itself.

In the case of underground mining vehicles this size vehicle is usually only required to traverse a rough-holed haul road.

Slightly lower density filled materials work best.

Step 4: Preparing the polyurethane material

The explosive foam filling material usually comprises

Component A

Polyol blend

Component B

Isocyanate

Both of these materials are kept in pasteurised tanks prior to processing.

Key factors

Material temperature

20–30°C

Viscosity

Accuracy

±5%

Mixing ratio

±1%

In the latest OTR Tire Foam Filling Machines automatic metering equipment is used, and success on this front means that ratio accuracy is maintained through the production process.

By 2026, as a result of rising mining volumes, systems with digitally-monitored dosing across the whole fill cycle that allow each filling cycle to be recorded should be in wide use on secondary fill machines.

Step 5: Filling the cavity by injecting through the Foam Filling Machine

This is the main event…

Equipment used

• OTR Tire Foam Filling Machine
• Foam Filled Tire Equipment
• Polyurethane Tire Flat Proofing Pump System
• High Capacity OTR Tire Foam Filling Station

Liquid polyurethane is injected through the valve orifice from the foam filling machine.

The material progressively displaces the air within the cavity until the whole volume is occupied.

Critical process parameters

Injection pressure

Typically of the order of 8–20 bar

Rate of fill

Variable and depends on the volume of the tyre.

Temperature of the material and quality of mixing need continuous monitoring.

Experienced operators discourage excessive speed of injection.

Many novices tend to suppose that if filling times are reduced a proportionate increase in productivity will follow.

Unfortunately, too great a speed of filling often results in some air being enveloped within the OTR tyres, and these voids do not necessarily become visible until the tyre is put into service and stabilised stress levels create local concentrations of imbalanced stresses.

A slowly fill-ing machine used slightly more regularly often discharges a better, if faster, tyre.

Step 6: Purging of air and eliminating voids

The air now trapped must escape during the filler-ing process.

With many modern units this is effected through a special vent valve.

Goal

Total occupancy of the cavity.

Risks of Insufficient Air Removal

• Internal voids
• Uneven load distribution
• Localized hot spot formation
• Premature tire failure

The use of vents for large mining tires must be more carefully considered since larger tires have a more complex internal geometry.

Step 7: Controlled Expansion Phase

Polyurethane begins expanding as soon as it is mixed.

The expansion stage determines the final structure of the cells.

Items to Monitor

• Internal pressure
• Expansion Rate
• Wheel deformation
• Material flow & properties

Advanced explosion-proof tire filling machine solutions now include real-time pressure monitoring and automatic shutdown protection.

This function is more useful when processing large mining tires with rim diameters over 25 inches.

Step 8: Curing Process

After the tire is filled it will enter the curing process.

Typical Cure Time

Cure Time Dependent Upon

Temperature

20 to 35°C

Humidity

Controlled

NOT in sun

Excessive heat will normally promote curing at the expense of longer term performance of the material – most operators do not appreciate this and find that, months later, at least one sidewall has ruptured.

The more stable the curing conditions are kept, the longer term performance (durability).

Step 9: Post-Cure Inspection

Every foam filled tire should get a post fill inspection before delivery.

Sample Items for Inspection

Weight

Is it full?

Surface

Any leaks or other problems?

Pressure

Structurally sound?

Balance

Is there even material distribution?

Ultrasonic inspection technology is becoming ever more predominant in premium foam filling facilities to check for hidden voids in large mining tires.

Step 10: Deployment in the Field and Monitoring Performance

When deployed on equipment, remain vigilant of the following as the workload mounts:

• Tire temperature
• Sidewall wear
• Tread wear pattern (overheating can be detected in general tread wear patterns)
• Handling issues (was it disproportionate?)
• Rim integrity

Typical Life Span

Most mining applications may expect to see:

3,000-8,000 hours of operation

Though actual life will vary according to:

• How much weight is being carried;
• How fast; the faster the moving parts, the higher the friction levels .
• What surface;
• Air temperature; hotter the air, heavier the workload on the tire
• Vehicle maintenance;

Applications Where Foam Filling is Not Ideal

Foam filling is indisputably the best answer in many circumstances, but it is not the cure-all for tireers who intend to foam fill whatever they can.

High Speed Highway Vehicles

Foam filled tires are hotter running tires at sustained speeds on the road;

Long Distance Transport Equipment

Heavy tires may take more fuel to move;

Machines Where Comfort is a Priority

Foamed tires do not absorb shocks as well as air filled tires; and

Applications Where Carrying Extra Weight Comes at a Cost

Filling tires take considerable weight; that added weight takes Away from the amount of weight that Goodyear construction tires can support ; unsprung weight is the main concern.

Knowing where the problems would crop up, will help in avoiding expensive mistakes about specifications.

EQUIPMENT WE’D RECOMMEND FOR MINING OPERATIONS

Small Service Shop Facilities

Also referred to as a “one stop shop”, or mobile service centers that tend to be multi bred to service a range of Fleet, ranging from Construction to General Manufacturing.

Desired Equipment

• Foam Filled Tire Equipment
• Polyurethane Tire Flat Proofing Pump System

Recommended Equipment for Regional Mining Contractors

Ideal Equipment

• OTR Tire Flat Proofing Liquid Filling Machine
• Automatic Metering system

Ideal Equipment for High Volume Industrial Operations

The Desired Equipment

• High Capacity OTR Tire Foam Filling Station
• Explosion Proof Tire Filling Machine Fill Solution
• Automatic Data Logging System

How Our Haifeng Automation can assist in mining projects foam filling tires

For Industrial tire, heavy equipment service contractors, and heavy equipment maintenance centers, the success of such a project is dependent not just on the foam filling equipment but also on the expert consultation provided by Haifeng.

Engineering Support

…continued

A literature review of how many of these engineering support elements you must be able to provide must emphasize:

• Production Capacity Assessment
• Material Compatibility Studies
• Tire Volume Estimate
• Plant Layout Design
• Operator Training
• PU Mixing Head Repair/Replacement
• Remote Diagnostics
• Long Term Spare Parts Requirements

Haifeng Automation, Haifeng PU Technology, Haifeng Engineering provide integrated brand solutions including OTR Tire Foam Filling Machines, Polyurethane Tire Flat Proofing Pump Systems, operator training, equipment retrofitting, and integrated turnkey polyurethane manufacturing systems for overseas markets.

For large mining contracts, an integrated engineering plant project is frequently able to deliver more consistently than simply buying the equipment without process integration.

Technology Trends Impacting Mining Tire Foam Filling in 2026

Smart Filling Systems

• Real-time data collection of pressure, temperature, and flow.

Digital Quality Traceability

• Every filled tire comes with a production history.

Low-Exotherm Formulations

• Heats less during curing.

High Performance Mixing Heads

• Greater consistency in material filling tires.

Remote Equipment Diagnostics

• Quicker fault finding, less-filled tire downtime.

AI Process Optimization

• Automated adjustment of fill based on tire size and material response.

All of these innovations are enhancing the consistency of large volumes of tires going off the line while reducing dependency on labour.

Decision Matrix for Selecting a Foam Filling Solution

FAQ

How long does-filled poly-foam last in mining tires?

Typically between 3,000 and 8,00O hours in any given application depending on terrain and load.

Will a heavier foam fill provide a longer life?

Not necessarily.

The volume is normally dictated by terrain and load considerations.

If you think of fill weight, the more polyurethane the more temperature generated, the more the vehicle in total weighs, the more stress to the drivetrain.

The mixing facility is set for a given end-use vehicle, and the final density must fit the machine and site.

Can I foam fill a damaged tire?

Unfortunately not.

Generally the foam fills the air chamber, but can do nothing for structural damage, such as minimum feature ‘Y’ when the sidewall has separated and all cords have been washed out to leave maximum feature ‘Z.’

What equipment would I use for filling an OTR tire?

Nominally an OTR Tire Foam Filling Machine, Polyurethane Tire Flat Proofing Pump System, dipping station, metering equipment, curing area, and inspection station.

How much does it cost to build a mining tire foam filling set?

Consumables aside, it depends on the volume of tires you wish to fill at a stretch, the degree of automation, tire width range through the plant, and daily material consumption for the filler.

Nevertheless a complete turnkey project would include the equipment itself, engineering design consultation, installation and commissioning and training of operators, a supply of spare parts, and ongoing after-sales technical support.