1 Introduction to the pipeline
2 Pipeline layout requirements
3 Determine the tube length
(1) According to the fixed piping path determined in Article 8.2, measure the length of the pipe on site, and pay attention to the influence of the radius of the elbow; (2) The influence of various types of pipe joints after being connected to the pipeline shall be taken into account; (3) The length of the pipe should be determined, cut and pre-installed section by section, so as to facilitate on-site adjustment according to the actual situation. If all of the pipes are cut off at once, the piping will be difficult when accumulated errors occur; (4) The cut short pipes should be used as far as possible in each place where short pipes are needed. If necessary, straight pipe joints can be used to lengthen them, but the number of joints on the pipe section should be less rather than more.
4 pipe cut off
(1) Use sawing machines or special pipe cutting machines to cut off the pipes. It is absolutely not allowed to use melting (such as flame cutting) or grinding wheel cutting;
(2) The incision should be flat, the flatness of the section should be no more than 1 mm, and the perpendicularity to the axis of the pipe should be no more than 1 degree;
(3) Use a file, scraper, etc. to remove chips and burrs;
(4) Use clean compressed air or other methods to remove the debris and rust attached to the pipe;
5 Tube bends
(1) Use a pipe bender for cold bending, not hot bending (large diameter pipes can be replaced by right-angle joints), and the bending radius should be more than 4 times the pipe diameter;
(2) The ovality (change of long and short diameter) at the bend is less than 10% of the pipe diameter, and no wrinkles can appear;
(3) If there is a joint at the pipe end at the bend, a straight pipe at the pipe end should be connected to the joint to avoid affecting the installation;
6 Pipe and joint welding
(1) Use tungsten argon arc welding or argon arc welding for back-sealing and arc welding backfill welding. When the pressure exceeds 21mpa, 5l/min argon gas should be passed through the tube at the same time;
(2) When the wall thickness of the pipe is greater than 2mm, a 35° bevel should be cut on the outer circle, and a 3mm gap should be left at the opposite side; when the pipe wall thickness is less than or equal to 2mm, the groove should not be cut, and a 2mm gap should be left at the opposite side; (3) The axes of the pipes must be coincident when they are aligned, the amount of misalignment is less than 15% of the wall thickness, and the deflection rate is less than 1:200;
7. Installation of pipe clamps
(1) The backing plate of the pipe clamp is generally welded to the structural member directly or through brackets such as angle steel, and the brackets are fixed with expansion bolts on the concrete floor surface or wall side;(2) When installing the pipe clamp, pay attention to leveling, that is, the installation surface is at the same height;(3) Spacing of pipe clamps: when the diameter of the pipe is ≤φ10, it is about 0.5 to 1 meter; when the diameter of the pipe is φ10 to 25, it is about 1 to 1.5 meters; when the diameter of the pipe is φ25 to 50, it is about 1.5 to 2 meters. A pipe clamp should be used on each side.
