Flame spraying equipment, plastic powder coating equipment

Based on the flame-spraying equipment developed by France’s SNMI and the UK’s SCHORI, our company has refined the design and adopted a unique, cart-based, high-capacity stainless steel powder feeder that can simultaneously supply powder to two spray guns.

Category:

High-power flame spray coating equipment

Key words:

Request for quotation E-mail:CarrieFeng07@outlook.com

Product Description

SX-6018 High-Power Flame Spray Plating Equipment

The powder-feeding structure, featuring a cyclonic fluidized bed combined with an adjustable Venturi-type powder suction device and an additional powder-cleaning injector, ensures that the feeder and long pipeline connecting to the spray gun remain free of powder buildup.

Since the powder feeder is not pressurized, powder can be added without stopping the gun, ensuring that the spray gun operates continuously, stably, and uniformly in all directions for extended periods. The spray gun is designed with a special gas-mixing method and a dual-layer shielding gas structure, preventing backfire during the spraying process.

The SX-6018 high-power flame-spray plastic coating equipment is currently the only flame-spray plastic coating system in China that offers the highest efficiency for large-area anti-corrosion field applications. It is suitable for on-site construction work on chemical plants, large containers, storage tanks, and oil and gas pipelines. This equipment has been included in the "Petroleum and Natural Gas Industry Standard of the People's Republic of China" SY/T XXXX－2007, which specifies the hot-applied polyethylene powder external coating for buried steel pipelines.

Composition: The complete set of equipment includes an SX6018 high-power flame spray gun, a powder feeder, piping, and air circuit regulating valves. Users need to provide their own 0.9 m³/min air compressor, oxygen, acetylene gas, an oxygen-acetylene pressure regulator, and associated pipelines.

Principle: Flame spraying involves using a specially designed powder-feed hose and a flame-spraying gun. The process utilizes an oxy-acetylene flame as the heat source and compressed air as a protective gas to generate a high-velocity jet stream. This jet stream heats the plastic powder being sprayed to a plasticized or molten state, which is then deposited onto a pre-treated work surface, forming a continuous, uniform, and pore-free plastic coating.

Features:

1. Plastic powder flame spraying, often referred to as flame plastifying, is primarily used for large-scale on-site plastic coating applications aimed at corrosion protection. It is characterized by a relatively thick coating, simple application process, lightweight and portable equipment, and the ability to be carried out directly on-site.

2. Compared to flame spraying, electrostatic powder coating, and fluidized-bed coating, flame spray plasticizing offers the following advantages:

1) The equipment has low cost requirements and does not need a specially designed spray booth or oven.

2) The equipment is lightweight and easy to carry, allowing on-site construction. Spraying can be carried out without being limited by the size or shape of the workpiece.

3) Construction can be carried out under environmental conditions such as 100% relative humidity and low temperatures.

4) Powder coatings contain no solvents, so there’s no need for drying or curing time after spraying—simply spray and use immediately.

5) It can be applied to a variety of substrate materials such as steel and concrete.

6) The coating is repairable: for small defects, simply heat the surface to perform repairs; for larger defects, the coating can be reapplied.

7) Easy to change powders and colors.

Application scope: Directly spray various plastic coatings that are resistant to acids, alkalis, and salts without the need for heating or curing equipment. This method is particularly well-suited for large-scale flame-spray coating applications on-site and can partially replace heavy-duty anti-corrosion coatings and fiberglass linings in terms of corrosion resistance performance, operational processes, and working environment.

Spraying parameters:

Item		Gas pressure parameters	Plastic powder varieties	Recommended preheating temperature for workpieces: ℃	Coating long-term use temperature ℃
Gas section	Acetylene gas working pressure MPa	0.10~0.12	High-pressure polyethylene	120~150	-70 to +60
			Low-pressure polyethylene	150~200	-70~+75
	Oxygen working pressure MPa	0.50~0.60	Nylon 11	170~230	-50 to +80
			Nylon 12	170~230	-50 to +80
	Dry, clean compressed air	0.40~0.60	Nylon 1010	210~250	-50 to +80
			Nylon 66	250~270	-50 to +80
	Spraying distance mm	150~300	Polyethylene PE Polyolefin PO Crosslinked polyethylene	180~250	-14 to +120
			Chlorinated polyether	170~230	-30~+120
Powder supply section	Powder deposition rate % Double-layer protective gas	85~95	Epoxy powder	150~200	80
			Ethylene-acrylic acid EAA copolymer Ethylene-vinyl acetate copolymer EVA	80~130	-45 to +70
	Recommended powder particle size (mesh)	Thermoplastic powder 80~140		Thermosetting powder 100~140

Note: All types of plastic powders must be stored in a dry, clean environment free of any foreign matter.

1. Flame temperature parameters: Acetylene gas + oxygen = 3,150℃; acetylene gas + air = 2,700℃; liquefied petroleum gas (LPG) + oxygen = 2,800℃; LPG + air = 2,200℃. If LPG is to be used instead of acetylene gas as the fuel gas, you must independently modify the acetylene gas pressure regulator to ensure that its thread matches the connection fitting on the LPG cylinder’s pressure regulator valve. For LPG, the pressure should be adjusted using an acetylene gas pressure regulator to a range of 0.1 to 0.15 MPa. When using oxygen or air as the assist gas, a pressure setting of 0.4 to 0.6 MPa is sufficient to meet the requirements of flame spraying.

2. Flame Spraying Process Flow: The flame spraying process mainly consists of the following steps: surface pretreatment of the substrate → workpiece preheating → flame spraying → inspection.

3. Pre-treatment of the substrate surface of the workpiece to be coated: For large components or containers, surface treatments such as sandblasting, grinding, and other processes (e.g., acid pickling, phosphating) can be used to remove oil stains, rust, or other corrosive substances from the surface. Process studies have shown that sandblasting and phosphating are most conducive to achieving strong adhesion between the flame-sprayed coating and the substrate.

4. Preheating: It is essential to preheat the surface of the workpiece to be coated to a temperature above the melting point of the plastic powder. For workpiece preheating, flame spray guns, flame remelting guns, and medium-frequency induction heating equipment are commonly used. The appropriate preheating temperature varies depending on the type of plastic powder, the shape and specifications of the workpiece, and the material properties of the workpiece itself. Based on research and practical experience, the specific preheating temperatures for different plastic powders are detailed in the spraying parameters mentioned above.

5. When the workpiece plate thickness is less than 3 mm, the initial preheating temperature of the workpiece (the region is approximately 1 m² of the base material = the melting point temperature of the thermoplastic plastic – 10 to 20℃).

6. When the workpiece plate thickness exceeds 3 mm, the initial preheating temperature of the workpiece (the area is approximately 1 m² of the base material = the melting temperature of the thermoplastic plastic + 10–20℃).

7. The preheating temperature inside concave workpieces and tank bodies is 10–20℃ higher than the preheating temperature for convex workpieces and flat parts.

8. When flame-spraying thermosetting plastic powders, the preheating temperature of the workpiece is related to the thickness of each coating layer. It is recommended that, when spraying thermosetting plastic powders, each coating layer should be relatively thin to facilitate the plasticization and crosslinking of the plastic coating.

9. The flame power of the spray gun is related to the gas pressure and flow rate supplied to the gun. A high-power gas flame can easily cause the plastic powder to burn and degrade, while a low-power gas flame may result in poor adhesion of the coating and incomplete plasticization. The magnitude of the flame power is primarily determined by the particle size of the plastic powder: coarse powder is best sprayed using a high-power flame, whereas fine powder is more suitable for spraying with a low-power flame.

10. Spray Distance: When the particle size of thermoplastic powder is approximately 60–140 mesh, the spray distance should be about 200–250 mm; when the particle size of thermosetting powder is approximately 100–180 mesh, the spray distance should be about 140–200 mm.

11. The protective gases typically used are compressed air, carbon dioxide, and nitrogen. Among these, carbon dioxide offers the best cooling effect; nitrogen is particularly suitable for protecting nylon materials during spraying. For coarse powders, the protective gas flow rate should be slightly lower, while for fine powders, it should be slightly higher. A protective gas pressure of 0.2 to 0.4 MPa is sufficient.

12. The typical powder feed rate for conventional flame spraying ranges from 60 to 300 g/min. If the coating thickness exceeds 0.3 mm, a pore-free coating can be achieved. Depending on the type of plastic, at a powder feed rate of 300 g/min and a film thickness of 1 mm, a single spray gun can achieve a spraying efficiency of 12 to 15 m²/hour.

13 Inspection: Select the thickness gauge and spark leak detector appropriately based on the coating thickness.

Powder-coated finished product display

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