1. Cutting steel pipes: According to the on-site survey sketch, draw lines on the selected steel pipes and cut the steel pipes according to the lines.
a. When cutting steel pipes with a grinding wheel saw, the steel pipes should be placed on the grinding wheel saw calipers, aligned with the drawn lines, and clamped to cut the steel pipes. When cutting steel pipes, the pressure on the handle should be even and not use too much force. After cutting the steel pipes, the iron film and burrs on the cross-section of the steel pipe mouth should be removed cleanly.
b. When cutting steel pipes with hand saws, the steel pipes should be fixed in the pressure pliers of the pressure case, the saw blades should be aligned with the drawn lines, and the saws should be pushed with both hands. The saw blades should be kept straight with the axis of the steel pipes, and the force of the push and pull saws should be even. The sawing should be cut to the end, and twisting or breaking is not allowed to prevent deformation of the cross-section of the steel pipe mouth.

2. Threading: Cut the steel pipe and thread it in batches according to the diameter of the steel pipe. Generally, the steel pipe with a diameter of 15-32mm should be threaded twice, the steel pipe with a diameter of 40-50mm should be threaded three times, and the steel pipe with a diameter of 70mm or more should be threaded 3-4 times.
a. Threading with a threading machine, clamp the steel pipe on the chuck of the threading machine, leave a proper length to clamp the chuck, align the plate sleeve number, install the die, align the scale with the steel pipe diameter, hold the fixed trigger, align the lubricant steel pipe with the thread head, start the machine and push the plate, and when the thread is sleeved to the proper length, gently release the trigger.
b. Use the manual threading plate to thread. First, loosen the fixed trigger, retract the threading plate to zero, install the die according to the order number, align the plate with the required scale, tighten the fixed trigger, put the steel pipe in the pressure case pressure clamp, leave the appropriate length to clamp, gently insert the threading plate into the steel pipe, make it moderately tight, then push the threading plate with both hands, put on 2-3 buckles, and then stand next to the threading plate. The force should be even. When the thread is about to be set, gently loosen the trigger, turn on the machine to retract the plate, and keep the thread taper.

3. Fitting steel pipe fittings: According to the on-site surveying sketch, the steel pipe with threaded threads is equipped with steel pipe fittings.
a. When assembling steel pipe fittings, the required steel pipe fittings should be inserted into the steel pipe thread to test the tightness (generally, 3 turns by hand is appropriate), and then the steel pipe fittings should be inserted after applying lead oil and hemp on the thread, and then tightened with steel pipe pliers to expose 2-3 turns of the thread, remove the hemp head, wipe off the lead oil, number and place in the appropriate position to wait for straightening.
b. Choose appropriate steel pipe pliers according to the size of the steel pipe diameter to be equipped with steel pipe fittings

4. Straightening of steel pipe sections: Straighten the steel pipe sections with installed steel pipe fittings before installation.
a. Apply lead oil on the thread of the steel pipe section with installed steel pipe fittings, connect two or more sections, and when connecting, not only the direction of the reserved opening of the steel pipe but also the tortuosity of the steel pipe should be taken into account. After aligning each other, turn the reserved opening direction to the appropriate position and keep it straight.
b. After the steel pipe section is connected, it is necessary to check whether the steel pipe diameter, reserved opening direction, and diameter change position are correct according to the planning drawings before straightening.
c. The steel pipe section should be placed on the steel pipe rack or steel pipe platform for straightening. Generally, two people are suitable for operation. One person visually inspects the end of the steel pipe section, and the other person hits the bend with a hammer. While hitting, observe, until the straightened steel pipe section stops without bends, mark the connection point of the two steel pipe sections, remove one or several sections, and then connect another section or several sections until the adjustment is completed.
d. For steel pipes with too many bends at the connection point of the steel pipe section or large diameter, the steel pipe can be heated to 600-800℃ (fire red) by oven or gas welding, and then placed on the steel pipe rack to roll the steel pipe continuously, and use the weight of the steel pipe to make it straight, or use a wooden board to pad the heated place and hit it lightly with a hammer to straighten it. After straightening, it should be rolled continuously before cooling, and when the temperature is about to reach the right temperature, apply engine oil to the heated place. All threads that are straightened by heating must be marked, removed, and re-coated with lead oil and hemp, and then the steel pipe section should be aligned with the mark and tightened.
e. When straightening the steel pipe section equipped with the valve, the valve cover should be removed first, the valve should be padded and then hit to prevent the valve body from cracking.
f. Galvanized carbon steel pipes are not allowed to be straightened by heating.
g. The steel pipe section is not allowed to be damaged when straightening.