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Technical Requirements for the Manufacturing of Membrane Walls (Screens) 1. Subject Matter and Scope of Application These technical requirements are based on ASME Volume I, covering the manufacturing, inspection, acceptance, marking, painting, and packaging of membrane walls (screens) for 1200 tbs/d alkali recovery boilers. 2. Referenced Standards Standards for raw material control; Technical requirements for welding of pressure components; Control procedures for heat treatment; Standards for non-destructive testing; Procedures for hydrostatic testing; Regulations regarding packaging and painting. 3. Technical Requirements 3.1 Materials 3.1.1 The materials and specifications of the tubes and flat bars used to manufacture membrane walls (screens) must meet the requirements specified in the design drawings. Any substitution of materials must be approved through proper procedures; substitutions for pressure-bearing materials require approval signed by AOSUN. 3.1.2 Welding materials (electrodes, wires, fluxes, etc.) must comply with the provisions outlined in the process documents. 3.1.3 Materials used for manufacturing membrane walls (screens) must undergo inspection upon arrival at the factory in accordance with G/Z54-2000; materials that do not meet these standards shall not be used in production. 3.2 Splicing of Tubes and Flat Bars 3.2.1 Tubes used to manufacture membrane walls (screens) should preferably be of full length; if this is not possible, one weld joint per tube is allowed (as specified in Annex 2.5, Clause 4). 3.2.2 Flat bars may be spliced together, but the splice welds must be fully penetrated, and their upper and lower surfaces must be smoothed out. The splice welds between flat bars and tubes must be offset from each other. 3.2.3 When manual welding is used to join flat bars to tubes, grooves must be made in the flat bars, with the type of groove determined according to the design drawings. 3.3 Welding 3.3.1 Welding procedure qualification and requirements for welding are specified in Q/Z55-2000. 3.3.2 Before welding, rust, oil, rust inhibitors, and other contaminants on the surfaces of the tubes and flat bars must be removed in accordance with the process documents. a. For submerged arc automatic welding, the penetration depth of the weld joint is specified in Figure 1 and Table 1: Table 1 L (m) L≤2 2 15 N Splicing not allowed 1 2 3 4 b. For manual welding, the penetration depth is specified in Figure 2 and Table 2: Table 2 Nominal outer diameter D Δf ≤60 Manual welding ≤0.5 Mechanical welding ≤0.3 60> D≤108 ≤0.8 108> D≤159 ≤1.0 159> D≤219 ≤1.5 D> 219 ≤2.0 3.3.4 Welding between flat bars and tubes should be done as double-sided continuous welding, with no missed welds allowed (Annex 27, 10.0). 3.3.5 The weld shape should be smooth and even; the weld surface must not have cracks, slag inclusions, crater defects, or undercuts (Annex 27, 10.0). 3.3.6 The weld surface between flat bars and tubes must not have individual pores larger than 2 mm in diameter. There must also be no clusters of pores (more than 3 small pores connected together) or rows of pores (more than 5 pores within any 100 mm of weld length). a. The longitudinal splice welds between fin segments should be continuous welds; single-sided continuous welding is allowed when the penetration depth of the continuous weld is at least 50% of the thickness of the fin tip. In such cases, intermittent welding should also be carried out on the back side, with each weld segment having a length of at least 100 mm, and the spacing between weld segments equal to the length of each weld segment. b. Longitudinal splice welds between fin segments must not have cracks, missed welds, or through-pores. The undercut depth of the weld must not exceed 1.0 mm. For general pores, the requirements specified in Table 3 must be met; if any of these requirements are not satisfied, the defective area must be removed (or ground away) and then rewelded. Diameter of pores Acceptable standards Single pore Multiple pores Φ