Heated surface ball

This is the first time I've heard of it, can you please share some information? :o

Can anyone tell me more specifically? Article 4.2.1 Inspection of heating surface pipes before installation should meet the following requirements: 1. The surface of the pipe should not have defects such as heavy skin, cracks, flattening and severe corrosion. When there are scratches, pits and other defects on the surface of the pipe, their depth should not exceed 10% of the nominal wall thickness of the pipe. 2. Alloy steel pipes should be subjected to spectral inspection one by one. 3. The shape of the convection tube bundle should be inspected and corrected. The school management platform should be flat and firm. The dimensional error of the lofting should not be greater than 1mm. The corrected tubes should match the solid line of the lofting. The local gap should not be greater than 2mm, and a trial installation inspection should be carried out. 4. The heating surface pipes should be arranged neatly, and the deviation between local pipe sections and the designed installation position should not be greater than 5mm. 5. The end face inclination of the expansion joint should not be greater than 1.5% of the nominal outer diameter of the pipe, and not greater than 1mm. Article 4.2.2 The expansion joint ends of pipes that have not been annealed shall be annealed. When annealing, do not use fuels with high sulfur and phosphorus content such as bituminous coal for direct heating. When the hardness of the pipe end is less than the hardness of the pipe hole wall, the pipe end does not need to be annealed. Article 4.2.3 When annealing the expansion joint end of the pipe, the heating should be uniform ； The annealing temperature should be controlled between 600 and 650°C and should be maintained for 10 to 15 minutes. ； The annealing length should be 100~150mm ； The pipe ends after annealing should be insulated for slow cooling. Article 4.2.4 Before expansion joints, the surface oil stains on the pipe ends and pipe holes should be removed and polished until they have a metallic luster. ； The grinding length of the pipe end should be at least the pipe hole wall thickness plus 50mm. After grinding, the thickness of the pipe wall shall not be less than 90% of the nominal wall thickness, and there shall be no defects such as peeling, dents, cracks, and longitudinal scratches. Article 4.2.5 The expansion pipe end should be selected based on the measured data of the polished pipe hole diameter and the pipe end outer diameter. ； The maximum gap between the expansion pipe hole and the pipe end shall comply with the requirements in Table 4.2.5. Article 4.2.6 During expansion joints, the ambient temperature should be 0°C and above. Article 4.2.7 Before formal expansion, trial expansion should be carried out. First, inspect, compare and observe the sample. The expansion opening should be free of cracks, the expansion joint transition part should be even and smooth, the bell mouth root and the pipe hole should be in good condition, and the contact marks and meshing conditions between the pipe hole wall and the outer wall of the pipe, pipe wall thinning and pipe hole deformation should be checked. A reasonable pipe expansion rate should be determined, and a complete construction process should be used to control the pipe expansion rate.