1. Confirm that there are sufficient number of bridge holes to ensure firm and reliable extension.

The aperture after drilling or reaming should be {{0}}.007 (0.18mm)~0.010 (0.25mm), which is larger than the outer diameter of the pipeline used.

3. If conditions permit, it is recommended to perform precision machining or rolling treatment on the inside of the plate holes to obtain a higher surface finish. This can also improve the tensile strength of the bridge.

4. Notching the plate holes can increase the mechanical strength of the expansion joint.

(1) Hydraulic expander: When the aluminum sheets in the copper tube are connected in series, all the elbows of the connecting box are welded, and through high-pressure liquid (such as water), when the water pressure rises to 1200-200kg/cm2, the copper tube is hydraulically expanded to make close contact with the aluminum sheets.

(2) Mechanical expander: Due to the soft state of copper tubes and the hard state of aluminum flakes, a mechanical expander is used. Mechanical force forcefully pushes the expansion head of alloy steel into the inner diameter of the copper tube, causing the copper tube to expand by 30-40 threads. This calculates the positive deviation of the outer diameter of the copper tube, the negative deviation of the inner diameter of the aluminum sheet hole, and the spacing between the piercing tubes to ensure a tight connection of the copper tube. The corresponding expansion coefficient is increased again, and this increased expansion is called interference fit.