An unstable ratio of components A and B when starting a high-pressure installation often leads to the formation of a sticky surface or bubbles on the finished coating. It is the dosing accuracy that is the critical parameter that determines the quality polyurea and the speed of her reaction. Unlike traditional spray guns, modern spraying machines require strict control of the temperature of the components and pressure in the hydraulic system, since the slightest deviation in parameters hydraulics may stop the polymerization process.
The majority of problems when working with two-component systems arise from improper preparation of equipment or the use of low-quality compressed air. The compressor must provide a stable air flow of at least 3-4 cubic meters per minute, otherwise the spray gun will not be able to create the necessary turbulence to mix the jets. If you notice that the spray pattern has become intermittent or has changed its geometry, first check the dryer filters and the pressure at the inlet to the device.
The design of modern machines allows the operator to manually adjust the balance of flows, but automation takes over control of the temperature in the hoses. Usage heated hoses is a prerequisite for working in the cold season, since the viscosity of the isocyanate increases sharply with decreasing temperature. Ignoring this fact leads to increased wear of plunger pairs and failure of expensive pump group seals.
Operating principle of high pressure units
The technology for applying polyurethane resin is based on mixing two liquid components under high pressure directly in the mixing chamber of the gun. The device consists of two independent pumping groups that supply components A (resin) and B (isocyanate) in a strict 1:1 ratio. The pressure in the system can reach 200 atmospheres or more, which ensures the finest dispersion of particles and their instant reaction upon collision.
The key element of the system is the heating unit, which maintains the temperature of the components in the range of 60 to 80 degrees Celsius. Temperature control necessary to reduce the viscosity of materials, especially if work is carried out outdoors at low temperatures. Without preheating, the components will not be able to fully mix, which will lead to defective coatings.
⚠️ Attention: Never start recirculating components without first warming up the hoses, this can lead to water hammer and rupture of the lines.
The circulation of materials occurs in a closed loop until the gun trigger opens. This allows you to maintain a constant temperature and the mixture is ready for application at any time. The operator controls the process through the control panel, where the target temperature and pressure values are set.
Classification of spraying apparatus
The market offers various types of installations, which are divided by the type of pump drive and the method of mixing the components. The choice of a specific type depends on the volume of work, the type of material used and the operating conditions of the equipment. For small objects, compact models can be used, while industrial waterproofing requires powerful stationary complexes.
The most common devices are pneumatically driven, where compressed air drives pneumatic piston pumps. Such systems are reliable, explosion-proof and easier to maintain. However, there are also electric models that are characterized by lower noise levels and the absence of the need for a powerful compressor to drive the pumps, although the compressor itself is still required for the gun.
The equipment is also divided into low and high pressure systems. For polyurea, it is critical to use exactly high pressure apparatus, since only they provide the required mixing quality without the use of additional solvents. Low pressure systems are more often used to work with polyurethane foams or less reactive compounds.
An important aspect is the mobility of the installation. Some models are trailer-mounted with their own generator and compressor, making them completely self-contained. Others are compact units that can be carried into an elevator and connected to external infrastructure on site.
Key Spray System Components
The efficiency of the entire installation depends on the consistency of the operation of all its components. Each component performs its own function, and failure of even one part can stop the entire process. Understanding the device helps you diagnose problems faster and perform preventative maintenance.
The list of main nodes includes:
- 🔹 Pump group — the heart of the apparatus is piston pumps that create operating pressure; they require regular lubrication and checking the condition of the seals.
- 🔹 Heating block — electric heating elements built into tanks and hoses ensure thermal stability of components in all weather conditions.
- 🔹 Spray gun - a complex mechanical assembly with a mixing chamber where the jets collide at an angle of 180 degrees.
- 🔹 Control system - electronic board or pneumatic valves that control the operation of heaters and pumps.
Particular attention should be paid to the hose line. This is not just a tube, but a complex structure with a built-in heating element and a thermocouple for feedback to the control unit. Damage to the hose insulation or kinking can lead to local overheating and coking of the material inside the channel.
Mixing chamber device
Inside the gun there is a replaceable chamber with two input channels located at an angle to each other. When the trigger is pressed, the components are fed towards each other, mixed and ejected through the nozzle. After releasing the trigger, a special rod closes the channels, stopping the flow, but without interrupting the circulation in the system.
Specifications and Settings
To obtain high-quality coating, the operator must be able to correctly configure the installation parameters. The main quantities monitored during operation are hydraulic system pressure, component temperature, and gun air pressure.
Below is a table of typical parameter values for various types of work:
| Parameter | Unit of measurement | Minimum value | Optimal value | Maximum value |
|---|---|---|---|---|
| Hydraulic pressure | Bar (atm) | 80 | 120-150 | 200 |
| Component temperature | Degree Celsius | 50 | 70-75 | 85 |
| Air pressure (gun) | Bar (atm) | 4 | 6-7 | 10 |
| Material consumption | kg/min | 2 | 4-6 | 10+ |
The pressure is adjusted by a regulator on the pneumatic drive of the pumps. It is important to monitor the pressure gauges on lines A and B: the difference in readings should not exceed 10-15 atmospheres. If the difference is greater, this indicates a clogged filter, worn valves, or a viscosity problem in one of the components.
Use only dry air for the pneumatics of the device. Moisture in the pump drive air can freeze in winter and block the operation of the air valve.
The temperature mode is set on the controller. Modern systems allow you to set separate temperatures for tanks and hoses, which gives flexibility when working with materials of different viscosities. It is not recommended to exceed the temperature of 85 degrees, as this may lead to degradation of the isocyanate.
Rules for preparation and maintenance of equipment
The durability of an expensive installation directly depends on the quality of its preparation for work and subsequent maintenance. Neglect of routine maintenance leads to rapid wear of the seals and pump group. The main enemy of equipment is moisture and mechanical impurities.
Before starting work, be sure to visually inspect all connections and hoses. Make sure that the coarse filters in the tanks are clean and the oil level in the pneumatic system lubricator is correct. Starting a cold device without pre-circulation can lead to damage.
- 🔸 Check the condition of the pump rod seals daily for leaks.
- 🔸 Once a week, lubricate the moving parts of the gun with a special lubricant recommended by the manufacturer.
- 🔸 After each shift, be sure to flush the system with a solvent or preservative liquid.
- 🔸 Monitor the operation of the air dryer and drain the condensate from the compressor receiver.
☑️ Operator’s daily checklist
Pay special attention to the cleanliness of the gun's mixing chamber. Residues of cured polyurea can disrupt the geometry of the spray pattern. Use special cleaning solutions and soft brushes without scratching work surfaces.
⚠️ Attention: When servicing the gun, always relieve pressure in the system and lock the trigger with a safety lock to avoid injury.
Typical faults and methods for their elimination
During operation, the operator may encounter a number of typical problems that affect the quality of the coating. The ability to quickly diagnose the cause allows you to minimize downtime and material consumption. Most problems are associated with an imbalance of components or temperature conditions.
If the coating is sticky or has poor adhesion, the mixing ratio is most likely incorrect. This may be caused by worn pump check valves or air leaking into the suction line. The reason may also be insufficient temperature of the components, due to which the polymerization reaction does not proceed completely.
A common problem is unstable blood pressure. A jump in the pressure gauge needle usually indicates cavitation (lack of material at the pump inlet) or dirty filters. Check the cleanliness of the screens in the tanks and make sure that the material has not thickened and flows freely to the pumps.
The main indicator of a problem is the color and structure of the foam during test spraying. Uniform fine-cell foam indicates proper operation, large bubbles or heterogeneity indicate a failure in the settings.
If knocking noises occur in the pump group, stop the device immediately. This may indicate dry operation or destruction of the lip seals. Continued operation in this mode will lead to cylinder scuffing and costly repairs.
Frequently asked questions (FAQ)
Can polyurea equipment be used to apply regular paint?
Technically this is possible, but it is not economically feasible. High pressure cleaners are designed for viscous, quickly reacting materials. For paints, low-pressure apparatuses are used, which are cheaper and easier to maintain. In addition, it is almost impossible to completely remove paint from a complex system, which will lead to damage to the expensive polyurea during the next job.
How often should the mixing chambers in a gun be replaced?
The service life of the mixing chamber depends on the abrasiveness of the fillers in the material and the thoroughness of washing. On average, one chamber is enough for 300-500 kg of applied material. Signs of wear include a change in the shape of the spray pattern and the inability to obtain high-quality mixing even at high pressure.
Do I need a special compressor to operate the device?
Yes, the demands on the compressor are high. It must provide not only the required pressure (usually 6-8 atm), but also a large volume of air (performance from 1000 l/min and above), since pneumatic pumps consume a lot of air. A high-quality dehumidifier is also critically important, since moisture damages pneumatics.
What to do if the device does not hold pressure?
First of all, check the check valves in the pump group - they often become clogged with crystals or dirt. The second reason is wear of the piston seals. The third is air leakage through leaky connections on the suction line from the barrels. Carry out diagnostics sequentially, starting with filters.
Is it possible to work with polyurea in winter?
Yes, it is possible, but additional insulation of hoses and barrels with material is required. The device must be designed to operate at low ambient temperatures. Often, operators build temporary hothouses or use heat guns to heat the application area, since the material on the surface cools instantly.