In order to ensure the quality of tube expansion, it is necessary to determine the tools, measuring tools, and operators before tube expansion

In order to ensure the quality of tube expansion, it is necessary to determine the tools, measuring tools, and operators before tube expansion

1. Tube expander

The selection of the expansion tube must comply with ZJB980001-87 regulations. The surface of the expansion beads and expansion rods of the expansion tube should be smooth, without grooves, scratches, or other phenomena. Before cleaning the parts, check whether the matching of each part is correct. The expansion rods cannot be bent, and the conicity is generally 1:25. The circular conicity of the expansion beads is half of the conicity of the expansion rods. When assembling the expansion rod and expansion ball, the axis has an angle of 1.5-2 °, and the expansion rod and expansion ball can basically maintain line contact to ensure the quality of the expansion joint.

2. Self made pipe fixtures and templates, pipe arrangement, and angle iron samples that can firmly stabilize the pipes.

3. Choose a self-produced "lathe style" pipe joint polishing machine, and fix the pipe head with a gantry clamp at the end, exposing a length of 200mm The actual polishing is 100-200mm, and the polishing relies on the motor installed on the sliding block to drive three movable grinding wheel blocks. The surface is polished according to the centripetal rotation force, and the polishing brightness is controlled based on the slider. Clean the inner diameter of the pipe with a half cone.

4. Grinding of pipe holes shall be carried out using inner circle grinding wrapped with fine sandpaper.

5. Other tools include a small wooden hammer, a plumb bob, an inner diameter dial gauge, a vernier caliper, non threaded synthetic cloth, CCLs, or gasoline.

6. The internal devices of the steam drum should be removed for cleaning and inspection of the steam drum pipe holes.

When inspecting, the protective coating on the pipe hole wall should be cleaned first, and the processing quality of the pipe hole wall should be checked. There should be no sand holes, dents, edge burrs, or longitudinal scratches: the depth of longitudinal or spiral scratches should not exceed 0.5mm, the width should not exceed 1mm, and the distance from the scratch to the hole edge should not be less than 1/3 of the thickness of the hole wall and should not be less than 4mm

If there is rust on the pipe hole wall, use a fine sandcloth or other tools that do not cause obvious scratches on the hole wall, and treat the hole wall until it emits a metallic luster. When the distance from the expansion tube is long, anti rust oil should be applied well.

7. Measure the diameter, conicity, and ellipticity of each pipe hole using an inner diameter dry section meter, and record them on the unfolded drawing or record table. The deviation should not exceed the specifications.

When the deviation exceeds this regulation, it should be negotiated with the boiler user unit for handling.

8. Defective pipe holes shall not be expanded until the defects are eliminated, and smaller defects can generally be repaired with a scraper. The machining quality, ovality, and taper of the pipe hole wall after using a scraper or other trimming tools should meet the regulations.

To prevent the surface metal of the pipe hole from oxidizing again, the time from cleaning the pipe hole to expanding the pipe should be shortened as much as possible.

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