Thermal Spray Safety and Protection
The thermal spraying process involves numerous hazardous factors, including high temperatures, high pressures, high-velocity particles, and hazardous gases. Therefore, safety and protective measures are essential components of thermal spraying operations. During thermal spraying, heat source temperatures can reach thousands of degrees Celsius. For example, the arc temperature in plasma spraying can exceed 10,000°C, and the flame temperature in flame spraying can reach 2,000-3,000°C. These high temperatures can not only cause overheating and deformation of the workpiece, but can also lead to safety hazards such as burns and fires for operators. Furthermore, high-velocity particles (reaching speeds of hundreds of meters per second) can cause mechanical injuries if they come into direct contact with the human body. Long-term inhalation of the metal fumes, dust, and hazardous gases (such as nitrogen oxides and carbon monoxide) generated during the spraying process can lead to occupational diseases such as pneumoconiosis and metal poisoning. Therefore, establishing a comprehensive safety and protective system that comprehensively protects both operators and the working environment is essential to ensuring the smooth operation of the thermal spraying process.
Personal protective equipment (PPE) is the first line of defense for operator safety and must be carefully configured based on the specific characteristics of the thermal spraying process. First, operators must wear flame-retardant protective clothing made from heat-resistant aramid fiber or asbestos. This effectively blocks high-temperature radiation and flying molten particles, preventing skin burns. For head protection, operators should wear a hardhat with a visor made of impact-resistant and UV-resistant tempered glass or polycarbonate. This protects the head from mechanical damage and protects the eyes and face from burns from high-temperature particles and harmful light. Respiratory protection is particularly important. Depending on the spraying material and the work environment, a dust mask, gas mask, or supplied-air respirator can be used. When spraying ordinary metal powders, an N95-rated or higher dust mask is sufficient. When spraying toxic metals such as lead and cadmium, or when using solvent-based paints, a gas mask or self-contained breathing apparatus is required to ensure that the inhaled air quality meets safety standards. Additionally, heat-resistant gloves and protective footwear are necessary to protect the hands and feet from heat and mechanical damage.
A safe and protective design for the work environment is crucial to mitigating risks during the thermal spraying process. Comprehensive planning is required, encompassing spatial layout, ventilation systems, and fire and explosion prevention measures. The thermal spraying work area should maintain a sufficient safety distance from other production areas, be clearly marked with warning signs, and strictly prohibit unauthorized personnel from entering. The ventilation system is crucial for controlling air quality in the work environment, and a combination of local exhaust and general ventilation should be employed. Removable exhaust hoods should be installed near the spray guns to directly extract dust and hazardous gases generated during the spraying process. General ventilation should be installed throughout the workshop to ensure air circulation and keep dust concentrations below national standards (for example, the time-weighted average permissible concentration for metal dust should not exceed 4 mg/m³). For flame spraying processes using flammable and explosive gases (such as acetylene and propane), the work area must be away from fire sources and equipped with explosion-proof electrical equipment and firefighting equipment (such as dry powder fire extinguishers and fire sand). Regular inspections of gas pipelines and valves are required to ensure tightness to prevent gas leaks and explosions. Furthermore, the work area floor should be constructed of non-slip and fire-resistant materials, and equipped with emergency flushing systems to ensure prompt response in the event of an accident.
Equipment safety and protection are crucial for preventing thermal spray accidents, requiring strict monitoring and maintenance of equipment operation. Thermal spray equipment’s electrical systems must comply with safety standards, equipped with overload and leakage protection devices, and regularly inspect the insulation of wires and cables to prevent electric shock accidents. High-voltage systems (such as the plasma spray power supply system and high-pressure gas pipelines) should be equipped with pressure relief valves and pressure gauges to ensure system pressures remain within safe limits and prevent equipment explosions due to excessive pressure. Spray guns, as direct operating components, require regular inspection and replacement of vulnerable components such as nozzles and powder feed mechanisms to prevent damage that could lead to deviations in particle spray direction or abnormal velocity, potentially causing personal injury. Furthermore, the equipment’s cooling system (such as the plasma spray gun’s water cooling system) must remain unobstructed, with the coolant flow and temperature regularly checked to prevent overheating and damage, or even fire, caused by insufficient cooling. During equipment operation, operators must strictly follow operating procedures and refrain from performing maintenance or adjustments while the equipment is running to ensure safe and stable operation.
Safety management and emergency response mechanisms are crucial components of a thermal spraying safety protection system, effectively preventing accidents and minimizing losses. Companies should establish a comprehensive thermal spraying safety management system, encompassing operating procedures, safety training, equipment maintenance, and work permits, ensuring that every aspect is clearly defined. Operators should receive systematic safety training to familiarize themselves with the hazards, protective measures, and emergency response methods of the thermal spraying process. Operators must pass the assessment before they can begin work. Regular safety inspections should be conducted to promptly identify and eliminate potential safety hazards, such as the integrity of protective equipment, the effectiveness of ventilation systems, and the safety performance of equipment. Furthermore, comprehensive emergency response plans should be developed, clearly defining the emergency response process, division of responsibilities, and rescue measures after an accident occurs. Regular emergency drills should also be conducted to enhance operators’ emergency response capabilities. For example, in the event of a fire, operators should immediately cease operations, use on-site firefighting equipment for initial extinguishing, and promptly call the fire department. In the event of burns, the injured area should be immediately rinsed with cold water and transported to a hospital for treatment. Scientific safety management and effective emergency response can maximize the safety of thermal spraying operations.
