Polyurea Spray Rigs

A polyurea spray rig, often called a mobile coatings unit or spray foam rig, is a trailer, truck body or container fitted with all the equipment needed to apply polyurea coatings, polyurethanes and spray foam away from a fixed shop. A rig carries the proportioner, power supply, compressed air, heated hoses, drums and support equipment, so a crew can arrive at a site and spray with minimal setup. Rigs are used by contractors who work on roofs, containment areas, tanks, bridges and vehicles in the field.

Typical rig layout

Most rigs are built into an enclosed cargo trailer or truck box divided into zones:

• Equipment area with the proportioner, controls and hose reel.
• Drum area with space for A and B drums, transfer pumps and drum heaters.
• Power area with a generator, often in a separate ventilated compartment.
• Air area with a compressor and air dryer.
• Storage for spray guns, parts, PPE and prep tools.
• Workbench and lighting.

Layout aims to keep drums close to the proportioner, minimize supply hose length, and separate the generator’s heat and exhaust from materials.

Main components

Proportioner

The heart of the rig. It meters the A and B components at the correct ratio, heats them, and pumps them at the required pressure. Proportioners range from low-pressure units to high-pressure machines with large heater capacity. See plural-component spray and low-pressure vs high-pressure polyurea equipment.

Heated hose and reel

A heated hose assembly, typically stored on a reel, carries material to the gun. Reels make it easier to deploy and recover long hose runs.

Generator

Supplies electrical power for the proportioner heaters, hose heat, compressor and lights. It must be sized for the combined load with margin. Generators are typically diesel, and exhaust must be routed away from the work area and drums.

Air compressor and dryer

Compressed air drives transfer pumps, drum mixers and air-purge guns, and supplies breathing air systems where equipped and approved. Air must be dry and clean, so rigs include refrigerated or desiccant dryers and filters (see compressed air cleanliness). Breathing air requires a dedicated, suitable system with appropriate filtration and monitoring.

Transfer pumps and drum conditioning

Drum transfer pumps, agitators, desiccant dryers and drum heaters keep material ready to spray.

Climate control

Insulation, heaters and air conditioning keep materials within their storage temperatures and protect electronics.

Spray gun and spares

At least one impingement mix spray gun plus spares, rebuild kits and cleaning tools.

Planning a rig

Points that buyers and builders usually consider:

1. Materials to be sprayed. Pure polyurea, hybrids and foam each have pressure, temperature and output needs. Confirm with the material manufacturer.
2. Output and hose length. Larger jobs need higher output; long runs need more heat and pressure capacity.
3. Power budget. Add the loads of all heaters and motors.
4. Weight and towing. Drums, generators and equipment are heavy. Trailer ratings and tow vehicles must match.
5. Ventilation and safety. Generator exhaust, fuel storage, chemical storage and fire extinguishers all need planning.
6. Serviceability. Equipment must be reachable for maintenance.
7. Training. Equipment operation and material application training are usually required by manufacturers.

Some coating manufacturers design and build rigs for their own materials. ArmorThane, for example, builds polyurea spray rigs in-house and requires training before anyone sprays its materials.

Operating practice

• Level the rig and chock wheels before starting.
• Start the generator and allow it to stabilize before switching on heaters.
• Condition drums and mix the B side as specified.
• Set proportioner and hose temperatures, then confirm pressures on a test spray.
• Record batch numbers, temperatures, pressures and ambient conditions.
• At shutdown, park pumps as the manufacturer instructs, grease the gun, and protect isocyanate from moisture.

Maintenance

• Follow the generator and compressor service schedules.
• Drain compressor tanks and service dryers.
• Inspect heated hoses, fittings and reels.
• Clean strainers and check pump packings.
• Keep a log of hours, faults and repairs.

See spray equipment maintenance.

Safety

• Store chemicals according to their SDS and keep incompatible materials apart (see safety data sheets).
• Keep the generator compartment ventilated and free of fuel leaks.
• Provide fire extinguishers, eyewash and first aid supplies.
• Use the respiratory protection required for isocyanate spraying (see isocyanate safety).
• Secure drums and equipment for transport.

Key terms

• Proportioner. The pump unit that meters A and B components at a set ratio and pressure.
• Primary heaters. Heaters in the proportioner that bring each component to spray temperature.
• Generator. Onboard power source that runs the proportioner, heated hose and air compressor.
• Air dryer. Equipment that removes moisture from the compressed air supply.
• Rig layout. How the trailer or box truck is arranged for drums, workbench, hose reel and heat.
• Data logging. Recording of pressures, temperatures and volumes, useful for quality records.

Frequently asked questions

Can one rig spray both foam and polyurea?

Many rigs are set up to do both, sometimes with separate proportioners or by changing materials and flushing. Confirm that equipment meets the requirements of each material.

Do I need a breathing air system in the rig?

For spraying isocyanates, supplied-air respirators are commonly required. A rig can include a breathing air system if it is properly designed and maintained.

Related entries

• Plural-component spray
• Proportioner troubleshooting
• Spray foam roofing
• Starting a coating business
• Heated hoses for plural-component spray (new)
• Drum transfer pumps (new)