Central Air-conditioning Construction Site Experience-Part 2

3. water system

(1) The diameter reduction of PP-R pipes must be less than 3% when hot-melted, and the installation must meet the technical requirements of the manufacturer.

(2) Casings must be installed for pipes passing through walls, PUC70 casings are used for De25 and De32; PUC110 casings are used for De40, De50 and De63; PUC133 casings are used for De75 and De90.

(3) L30 angle steel is used for pipe support indoors, and the finish paint is painted with aluminum powder. Use L40 angle steel outdoors. Large pipes must use channel steel brackets.

(4) The pipe support must be sprung before installation, the spacing is less than 800mm, and it must be evenly divided on the same plane, and the form of supports in the same area should be consistent.

(5) The pipeline installation of the pipeline well should be coordinated with the cooperating unit to avoid staggered influence;

(6) The installation position of the pipe support is more than 150mm and less than 300MM from the PP-R pipe elbow. The pipe support shall be installed upright and shall not be skewed.

(7)  The centering of the pipe support must be consistent with the reserved pre-buried holes, and the pipe installation must be horizontal and vertical.

(8)  After the water pipe is installed, it must be flushed and pressure tested. The test pressure is 1Mpa, keep the pressure for 10 minutes, and the pressure must not drop. Then reduce the pressure to 0.6Mpa, stabilize the pressure for 60 minutes, the pressure must not drop, and the appearance inspection is qualified if there is no leakage. Insulation can only be carried out after passing the inspection. For high-rise pipeline pressure, select 1.5 times the working pressure for pressure test.

(9) An automatic exhaust valve must be installed at the highest point of the chilled water pipe, and connected to the condensed water pan of the nearby fan coil unit with a hose or connected to the condensed water pipe. A drain valve shall be installed at the lowest point of the chilled water pipe.

(10) The hot-melt connection of PP-R pipes should meet the following requirements:

a. The selection of the fuser should be appropriate, the die head should be in good condition, and the working temperature should be 230-260 degrees. The fuser cannot be operated until it has reached the set working temperature.

b. The cutting of the pipe should use special pipe shears, hacksaw or pipe cutting machine. After cutting, the burrs and burrs should be removed from the cut section, and the sectional surface of the pipe must be perpendicular to the pipe axis.

c. Before welding, the dirt on the connecting end faces of pipes and pipe fittings must be removed to ensure that they are clean, dry and oil-free.

d. (4) When hot-melting, control the hot-melt depth and reduce the diameter reduction rate.

e. (5) When welding elbows or tees, attention should be paid to their direction, and auxiliary marks can be used to clarify their positions in the straight direction of pipe fittings and pipes.

f. (6) When heating, the pipe end should be introduced into the heating jacket without rotation, and inserted to the specified depth. At the same time, push the pipe to the heating head without rotation to reach the specified depth, and the heating time should meet the requirements.

g. (7) After the heating time is up, immediately remove the pipe and pipe fittings from the heating jacket and heating head at the same time, and insert them to the specified depth in a straight line without rotation quickly, so that a uniform flange is formed at the joint.

h. (8) Within the specified processing time, the newly welded joints can be slightly corrected, but rotation is strictly prohibited.

i. (9) When the pipeline is installed, it must not be twisted axially, and it is not suitable for forced correction.

j. (10) When the pipeline is installed, the mouth of the pipe that is not closed must be tightly sealed to prevent debris from falling into the pipe.

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