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Project Category

Main project classification

Dongguan ventilation duct project


Dongguan ventilation duct process:

1) Process flow

Installation preparation → prefabrication → dry pipe installation → riser installation → branch pipe installation → pipeline pressure test → pipeline flushing → pipeline anticorrosion and insulation.
2) Technical quality requirements
Welding of seamless steel tubes shall meet the following requirements:
a. The seamless steel pipe adopts the manual arc welding process, the pipe wall thickness is ≤ 4MM, and the butt joint is used, and no groove is required. If the wall thickness of the pipe is> 4MM, a "V" -shaped groove welding is performed uniformly.
b. The misalignment deviation of the opposite side of the pipe should not be greater than 20% of the thickness of the pipe wall and not greater than 2MM. Adjust the gap of the opposite side, and the method of heating and twisting the pipe must not be used.
c. The welding slag of the butt weld of the steel pipe shall be cleaned away, and the defects of appearance inspection shall be repaired.
d. The butt weld of steel pipe should not be at the bend. When the joint is connected, the longitudinal weld of the pipe should be staggered at the mouth of the pipe, and the longitudinal weld should not be at the bottom of the pipe.
e. Open the branch nozzle on the main pipe. The branch nozzle should be saddle-shaped. The main pipe opening should be oval. The branch pipe should not be inserted into the inner wall of the main pipe.
f. The steel flange must be continuously welded inside and outside.
g. The inner weld of the flange shall not protrude from the sealing surface or the inner wall of the pipe, and the outer weld shall not prevent the hexagonal head of the bolt from flat against the flange.
h. For the pair of flanges, the two sealing surfaces shall be parallel to each other, and the deviation of the screw holes shall not be greater than 5% of the hole diameters, and the bolts shall be allowed to penetrate freely.
i. The thickness of the flange gasket is 2MM, the diameter is> 350, and the thickness is 3MM.
j. The inside and outside diameter of the gasket is the same as the inside and outside diameter of the flange sealing surface.
k. Only one piece of gasket should be placed, and no additional cracks should be placed.
l When the bolts are tightened, they should be tightened symmetrically and crosswise in two to three times to make the bolts uniformly tight.
M. The parallel deviation of the sealing surfaces of the two flanges after tightening should not be greater than 1.5 / 1000 of the outer diameter of the flange, and not greater than 0.2MM.
U-PVC, PPR pipe connection should meet the following requirements:
a. The mouth of the pipe should be filed with a medium plate file to a nearly 150 bevel, and the debris should be removed.
b. The bonding surfaces on the inside of the socket of the pipe fitting and the outside of the pipe socket should be wiped clean. If there is any oil, use an organic solvent to clean it.
c. The depth of the pipe inserted into the socket should be inserted once, and the depth of the bonding surface should be marked. The insertion depth is required to be not less than that required by the specification.
d. When applying the adhesive, apply the socket first, and then apply the socket, apply evenly and appropriately, and do not miss the application. When the annular gap of the socket is large, two coats are allowed, but the second coat must be painted after the first adhesive is dried. If the ring clearance is too small, sanding with sandpaper is allowed. After grinding, the debris should be removed.
e. When the socket is connected, pay attention to the orientation of the pipe fittings, the axis is aligned, and squeeze it to the marked depth for 2 to 3 minutes. The curing time is 24 hours.
f. The temperature control of the PP-R pipe should be in accordance with the requirements during thermal welding, and overheating or low temperature is strictly prohibited.
Galvanized steel pipe connections shall meet the following requirements:
a. Welding is strictly forbidden for galvanized steel pipe connection, and screw connection is adopted uniformly.
b. Pipe thread processing should be regular, if broken or missing, it should not be more than 10% of the total number of threads. The effective length of the pipe thread allows for a deflection.
c. The pipe thread connection packing adopts fine linen thick white paint or PTFE raw material tape. The packing should be wound tightly with 3 ~ 4 layers along the thread. It is strictly forbidden to squeeze the packing into the pipe.
d. After the pipe fittings are tightened, the exposed packing should be cleaned up, and the thread-proof paint should be exposed.
The thin-walled copper pipe connection shall meet the following requirements:
a. The thin-walled copper pipe connection is made of socket silver-copper brazing.
b. The surface of welded joints should be polished with sandpaper. There should be no longitudinal scratches. Oil stains and oxide films should be removed.
c. When welding, the temperature of the weldment shall be uniformly increased, and the heating time of the weldment shall be as short as possible.
d. After the weldment is completed, the weldment must be cooled below 3000C before it can be moved.
e. The oxide and residual flux on the weld surface should be removed.
Flange connection uses loose flange.
The stainless steel pipe connection shall meet the following requirements:
a. The groove requirements for stainless steel pipes are the same as those for carbon steel pipes.
b. It is strictly forbidden to strike directly on the surface of the stainless steel pipe with an iron hammer. A wooden hammer or rubber hammer shall be used to avoid damaging the oxidation protection of the stainless steel surface.
c. It is strictly forbidden to cut the opening by gas cutting. Can be cut with stainless steel electrodes or using a plasma cutter. After the stainless steel tube is cut, it needs to be degreased with acetone, then washed with white cat detergent, cleaned with water, and then dragged clean with a dry light cloth and sealed for use.
d. The stainless steel pipe must not be in direct contact with the carbon steel bracket, and should be isolated by plastic or rubber gaskets.
e. Before welding, the oil should be degreased and cleaned. After welding, the stainless steel wire brush should be used to remove the oxide layer and flux.
When the pipes or fittings are aligned, the inner wall should be flush, and the amount of misaligned edges at the mouth should not exceed 10% of the wall thickness, and not more than 1MM.
Source: Time: 2012-4-13 0:42:07
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