Steel tube surface treatment

The surface treatment of steel pipes plays a critical role in ensuring the effectiveness and durability of the epoxy powder coating. To achieve optimal results, the anti-corrosion production line is equipped with two shot blasting and descaling machines arranged in series. The first machine utilizes steel shots to effectively remove rust and scale from the pipe surface, while the second one employs steel grit to create a roughened texture that enhances the adhesion of the powder coating. Both the steel shots and grit are manufactured in France, ensuring high-quality standards. The steel shots have a hardness range of 48–52 HRC, while the steel grit has a slightly higher hardness of 53–57 HRC. The selection of these materials takes into account the strength and hardness of the steel pipe, as well as the recyclability of the media, which helps reduce costs and environmental impact. The number of times the media can be reused and its effect on the lifespan of the blast blades are also considered during the selection process. After processing through both machines, the surface of the steel pipe reaches a derusting grade of Sa2.5 to Sa3.0, with an anchor profile depth of approximately 80 micrometers—well within the standard requirement of 40–100 micrometers. Phosphoric acid is used for pickling, with a concentration of 10% (the manufacturer recommends 5–20%). For chromate treatment, the concentration is set at 10% (factory recommendation ranges from 5–50%). The salt content on the steel pipe's surface is tested using chemical reagents to ensure proper cleanliness. The heating temperature depends on factors such as the pipe diameter, wall thickness, and the thickness of the anti-corrosion layer. Based on the manufacturer’s guidelines, the heating temperature is typically maintained between 235°C and 245°C. The production speed is adjusted according to the gelation and curing time of the powder. A differential scanning calorimeter (DSC) is used to verify the curing time: 605 seconds at 235°C and 405 seconds at 245°C, ensuring that the coating meets the required curing specifications. A total of 24 spray guns are used to apply the powder coating, with flow control mechanisms in place to maintain even thickness across the pipe surface. Most of the sprayed powder adheres to the pipe, minimizing waste. In case of defects, a two-component liquid powder repair material is used. The repair process involves sanding the affected area and surrounding region with a file or sandpaper, followed by applying the mixed repair material with a spatula to ensure a smooth and slightly thicker finish than the original coating. Once the repaired area is dry, an EDM (electrical discharge machining) inspection is conducted to check for any leakage points. If no leaks are detected, the coating is considered合格 (qualified).

Test Weight Water Bags

Test Weight Water Bags are also called water weights, load test water bags, lifting water bags, etc. A weighing water bag is mainly used in ship cranes, shipyard cranes, port cranes, offshore platform cranes, gantry cranes, driving cranes, davits, etc., lifting equipment for load detection. It is more efficient, safer and cheaper to detect than traditional solid weights.

● High-frequency welding is used to make the DOING Load Testing Water Bags, and its outside is wrapped in high-strength fiber slings.

● Crane Water Bags are made of high-density composite materials (PVC, TPU) with superior sealing and corrosion resistance. It can be used at -30°C to 70°C, and it will not be unable to use normally due to seasonal changes. The material is reinforced with anti-freezing, anti-oxidation, and anti-ultraviolet properties. It is not affected by seawater, chemicals, agents, oil stains, acid and alkali and aquatic organisms.

● Water Bags for Weight can be folded during transportation, which greatly reduces space. Simple operation, light weight, small size, economical and practical, and long service life.

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