Production of wear-resistant spherical elbows

The production of elbow-shaped bends involves welding a hollow sphere. With a hollow steel shell sphere, welding in the inlet and outlet pipes forms a spherical elbow. Therefore, manufacturing hollow spheres is the key to producing spherical elbows.

Ceramic-lined composite pipes are fundamentally different from traditional steel pipes, wear-resistant alloy cast steel pipes, cast stone pipes, as well as steel-plastic and steel-rubber pipes. The outer layer of the ceramic steel pipe is a steel pipe, while the inner layer is corundum. The Vickers hardness of the corundum layer ranges from 100 to 1500 (with a Rockwell hardness of 90–98), which is equivalent to that of tungsten-cobalt hard metals. Its wear resistance is more than 20 times higher than that of carbon steel pipes, and it performs far better than corundum grinding wheels made by conventional bonding methods. Corundum grinding wheels remain the primary grinding wheels for grinding hardened steel in various grinders. The corundum layer in ceramic steel pipes can wear away the corundum grinding wheel. The wear resistance of ceramic steel pipes relies mainly on the several-millimeter-thick corundum layer on their inner surface; this layer has a Mohs hardness of 9, second only to diamond and silicon carbide. Among all oxides, it possesses high hardness.

Production requirements for ceramic wear-resistant ball elbows: In pneumatic conveying systems, ordinary elbows are components that wear out very quickly. When the gas mixture flows through a corner, the force of inertia causes it to scour against the outer surface of the elbow, leading to rapid wear in that area and reducing its service life. The design of the ceramic wear-resistant ball-shaped elbow overcomes the drawback of rapid wear associated with ordinary elbows. As air flows into the ball-shaped elbow, it finds it difficult to reach the inner surface of the sphere; instead, it frictionates with the vortices inside the sphere. As a result, the direct wear caused by the fluid on the sphere is reduced due to this buffering effect. The production requirements for ceramic wear-resistant ball elbows are as follows: The wear-resistant ball elbows purchased consist of a central spherical body along with straight pipe sections at both ends, with the metal components being seamless steel pipes and steel balls, respectively. The straight pipe section is lined with corundum ceramic, and welding grooves are required at both ends of the pipe to facilitate welding and installation. 2. The inner sphere of the wear-resistant ball-shaped elbow is lined with 92 alumina ceramic (92 porcelain) tiles. All linings shall be ceramic-dense with a smooth surface; grooves, bubbles, or separation of the wear-resistant layer from the steel pipe are not permitted. The wear-resistant ceramic layer on the lining is uniform, offering good wear resistance; its average thickness is not less than 6 mm, its Mohs hardness is above 9.0, and the total wall thickness is 14 mm ； The inner diameter of the pipe is ±2 mm, while ensuring the thickness of the wear-resistant ceramic. The strength of ceramic-lined composite steel pipes is not less than 1100 kg/m3; the density of the ceramic layer is not less than 3.6/cm2, the compressive shear strength is 15–20 Mpa, and the compressive strength is 300–350 Mpa. 3. The length of the straight sections at both ends of the spherical elbow shall be no less than 400 mm. A short connection pipe with a diameter of DN40 and a length of 50 mm is provided at an angle of 180° in the outlet pipeline as a supplementary air supply pipe; the sealing method for this short pipe is internal threaded plug sealing. 4. For ceramic wear-resistant ball-shaped elbows, two layers of rust-inhibiting primer and two layers of topcoat in sea gray color (B05 GSBOS-1426-2001) shall be applied; the thickness of the paint layer shall be no less than 0.2 mm, with full integrity of the paint surface ensured. In prominent positions on the outside, markings such as \"elbow number, pipe connection specifications, angle, radius of curvature, and direction of fluid flow\" are indicated using white paint. 5. Quality acceptance standards: At the time of delivery, a quality inspection report issued by a municipal or higher-level quality inspection agency for the ceramic wear-resistant ball elbows in the same batch must be provided. Due to their advantages such as simple manufacturing, easy installation, and good durability, ceramic wear-resistant ball-shaped elbows and tees are used as substitutes for pipe elbows and tees in pneumatic conveying systems for cement and raw materials as well as in power plants. They are thus being increasingly employed in the pneumatic conveying processes of large and medium-sized cement plants and power plants.