How should the technical requirements on the tube sheet processing drawings be specified?
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For components with special processing requirements, the technical specifications must be clearly specified in the drawings. On the tube sheet drawings, what aspects should be considered for the technical requirements? What are the specific requirements? First, let’s take a look at the general requirements for tube sheet processing: 1. Before processing, the unevenness of the tube sheet should be kept below 1‰ of its outer diameter, with a maximum value of 1.5 mm; 2. The sealing surface or end face of the tube sheet must be perpendicular to the axis, and the tolerance for this perpendicularity should meet the requirements of grade 9 as specified in the current standard **“Tolerances for shape and position – Unspecified tolerances” GB/T1184; 3. The holes in the tube sheet must also be strictly perpendicular to its sealing surface or end face, with the tolerance for this perpendicularity meeting the requirements of grade 9 as specified in the standard **“Tolerances for shape and position – Unspecified tolerances” GB/T1184; 4. During machining, it is essential to strictly control any deformation of the tube sheet. During the machining process, coolant can be applied, and the depth of cut and feed rate should be controlled. During drilling, it is not advisable to drill in one specific area; instead, drilling should be carried out in a distributed and symmetrical manner. 5. The tolerance requirements for pipe holes and pipe bridges must be met; when the thickness of the tube sheet is greater than 150 mm or the number of pipe holes exceeds 2000, CNC drilling is recommended. 6. After processing, the surface roughness of the pipe holes must meet the requirements specified in the design drawings. Process measures should be taken as necessary to ensure this; 7. The sealing surface must be free from defects such as grooves, scratches, and dents. Additionally, special requirements for the material must be considered, such as whether splicing of the tube sheet is permitted. Therefore, the technical requirements on the tube sheet drawings can be specified from the above perspectives; if the product has any other special requirements, those will be specified separately.
When establishing the technical requirements for the fabrication drawings of tube sheets, detailed specifications should be provided in the following areas: 1. **Dimension and flatness control**: – Before processing the tube sheet, its flatness should be kept at less than 1‰ of its outer diameter, with a maximum value of 1.5 mm. 2. **Verticality and tolerance requirements**: - The sealing surface or end face of the tube sheet shall be perpendicular to the axis, and its verticality tolerance shall meet the requirements of tolerance grade 9 as specified in GB/T1184. - The verticality of the tube sheet holes shall also meet the same standards. 3. **Processing process control**: - During machining, processing deformation must be strictly controlled, which can be achieved by using coolant and regulating the depth of cut and feed rate. - When drilling, avoid concentrating drilling in one area; instead, drill in a distributed and symmetrical manner. 4. **Tolerance requirements for tube holes and tube bridges**: - When the thickness of the tube sheet exceeds 150 mm or the number of tube holes is more than 2,000, CNC drilling should be used to ensure accuracy. 5. **Surface Treatment and Quality Control**: - The surface roughness of the pipe holes after machining should meet the requirements specified in the design drawings; appropriate processing measures should be taken as necessary to ensure quality. - The sealing surface must be free from defects such as grooves, scratches, and dents. 6. **Material and structural requirements**: - Special requirements of the materials must be taken into account, such as whether splicing is allowed or not. Through the detailed specifications in the aforementioned aspects, the quality and precision of tube sheet processing can be ensured to meet the requirements of design and use. If the product has any other special requirements, they should be specified separately on the drawings. .