Analysis and solutions of common faults of polyurethane spraying machines

Polyurethane spray machines are widely used in building insulation, anti-corrosion, waterproofing, cold chain, ships and industrial equipment, and their performance stability is directly related to construction quality and efficiency. This article will start with the core components such as the spray host, feed pump, booster pump, spray gun, and pipeline, and deeply analyze the common faults in polyurethane spray equipment and their solutions to help practitioners quickly troubleshoot and effectively respond in daily operations.

1. Common failures and solutions of lifting pumps

1. Unable to start

• The oil cup is too tight, causing the lifting shaft to lock;
• Crystals formed on the lifting shaft, causing it to get stuck;
• The reversing rubber cover falls off or the “O” ring is not sealed tightly;
• Black and white material is inserted incorrectly or there is foaming in the pump;
• The black material solidifies in the pump;
• There is no gas source or the gas source pressure is insufficient;
• The outlet filter is clogged;
• The friction resistance of the air motor piston is too large;
• The spray gun does not discharge material from a certain channel, affecting the operation of the pump;
• The return spring in the cylinder has failed.

Solution : Check and adjust the oil cup seal; remove crystals; replace seals; check the air source and air path; clean the pump body and filter device.

2. Leakage

• Wear of “O” ring or “V” ring;
• The reversing rubber cover is aging;
• There is air leakage at the thread or interface of the reversing assembly;
• The reversing assembly falls off.

Solution : Replace the seal, check and tighten the threaded parts.

3. Leakage

• Material leakage at the inlet or outlet;
• The clearance of the air motor cylinder is too large;
• The spray gun is clogged, causing back pressure;
• The seal at the lifting shaft fails.

Solution : Tighten the oil cup, check and replace the sealing ring; check whether the gun head is blocked.

4. Violent beating

• The raw material barrel is out of material;
• The pump bottom is clogged;
• Abnormal viscosity of raw materials;
• The lifting bowl is damaged or falls off.

2. Booster pump failure and abnormal pressure

1. Leakage problem

• The oil cup has insufficient pressing force;
• Seal wear;
• Black material crystallizes on the axis;
• The lower valve body or ball bowl is not sealed tightly;
• The lifting bowl is damaged or the supporting parts are broken;
• The “O” ring at the bottom of the booster pump is damaged;
• Nuts are loose or parts are falling off.

Solution : Replace the seal, remove crystals, check and tighten related components.

2. Unstable pressure

Reason 1: Spray gun part

• The gun tip aperture is uneven;
• The gun body filter is clogged;
• Friction parts are clogged;
• There is local blockage before and after the material valve;
• The discharge hole is not aligned with the mixing hole;
• There is residue in the mixing chamber of the gun tip;
• Friction causes serious leakage.

Reason 2: Raw materials and equipment problems

• The viscosity of the raw material is too high;
• White material temperature is too high or too low;
• Insufficient pipe heating or temperature control failure;
• The raw material pressure gauge is damaged;
• Heater failure or blockage by foreign matter;
• The raw material tube is too thin or has dead corners;
• The booster pump fails or the gas source is insufficient;
• The pressure setting of the triple pressure reducing valve is too low;
• The air compressor is not supplying enough air or there is water in the air line.

3. The host cannot start

1. Electrical failure

• The emergency stop switch is not released;
• The proximity switch is damaged or offset;
• The two-position five-way solenoid valve fails;
• The control system fuse is blown;
• The control system power supply is connected incorrectly or burned out.

2. Gas circuit failure

• The solenoid valve is clogged or frozen;
• O-ring failure;
• The air motor is short of oil;
• The cylinder screws are loose.

4. Analysis of spray gun failure

1. The spray gun leaks, is blocked, or cannot spray.

• The gun head is not tightly sealed or is worn due to friction;
• The motor overheats or stalls;
• The feed pipe is blocked;
• Regulating valve failure;
• Friction and shell leakage;
• There is solidified residue in the mixing chamber of the gun tip.

2. Unable to reset after pulling the trigger

• The piston “O” ring is leaking;
• The tail cover is not adjusted properly;
• The spring force is insufficient;
• Gas path obstruction;
• The piston resistance is too large;
• The friction attachment is not tightened, resulting in jamming;
• There is foreign matter stuck in the slide bar.

5. Pipeline and mixing issues

• The raw material barrel is sucked empty;
• The pump bottom and outlet filter are clogged;
• There is backflow or cross-flow in the pipeline;
• Check valve failure;
• The pressure of a certain raw material is too high;
• No heating or heater failure;
• Temperature sensor failure;
• Wrong power connection (220V connected to 380V);
• Black and white material heater failure.

Conclusion

The polyurethane spray machine system is complex and involves multiple precision subsystems. Any minor fault may cause the entire machine to stop working or even waste raw materials. Through systematic troubleshooting and standardized maintenance, most faults can be effectively prevented or quickly resolved. It is recommended that operators regularly check the status of the equipment, keep the raw materials clean and the proportions accurate, and strictly follow the operating procedures in accordance with the operating specifications to ensure safe, efficient and reliable spraying construction.