How is the PERT pipe welded to the PPR hot melt welding temperature?

1. Material:

(1) Commonly used geothermal installation pipes

There are two kinds, PE-RT and PEX1, PE-RT high temperature resistant polyethylene pipe, PE polyethylene plastic.

The welding process is also very simple, and it can be welded by a common PPR hot melt machine. The heat capacity of the PERT is between 220 and 240.

1. PEX cross-linked polyethylene pipe, PE-polyethylene plastic, X-crosslinking;

PEX pipe outlines ordinary high-density and medium-density polyethylene (HDPE and MDPE) pipes. The macromolecules are linear structures. The disadvantages are poor heat resistance and creep resistance, because ordinary PE pipes are not suitable for waters higher than 45 degrees. Cross-linking is a method of PE modification. After cross-linking, PE becomes a three-dimensional network structure of cross-linked polyethylene (PEX), which greatly improves its heat resistance and creep resistance, and at the same time, aging resistance, Mechanical properties and transparency have all been significantly improved.

2, PEX is divided into A, B, C, three, PEX-A, PEX-B, PEX-CPEX-A: peroxide cross-linking degree: more than 70% PEX-B: silane water cross-linking cross-linking Degree: more than 65% PEX-C: radiation cross-linking and azo cross-linking degree: more than 60% low cross-linking degree or no cross-linking degree: plastic tube is soft, toughness is too large; cross-linking degree is too high: plastic tube Harder; no toughness; therefore, the degree of cross-linking should be between 80% and 90%.

3, hot creep: lower is better, the heat deformation rate is low, the thermal expansion is small, the tensile and compressive force of the pipe is small during use;

How to distinguish between the advantages and disadvantages of the pipe:

1. Appearance: the inner and outer walls are smooth, the pipe wall is uniform, no bubbles, and the bending phenomenon;

2. The degree of crosslinking is consistent, and the plastic raw material and the crosslinking agent are thoroughly mixed in the extruder production process;

3. Uneven wall thickness of the pipe: The mold of the inner and outer walls has not been carefully adjusted and is not concentric;

4. Reasons why the inner and outer walls of the pipe are not smooth:

A. Failure to regularly clean the residue on the mold as required

B. The temperature of the mold head is not well mastered.

5. Air bubbles: Because the machine is now well sealed and has detection instructions, it is not easy to have air in, and the possibility of generating bubbles is small;

6. The water injection pressure test is carried out before packaging, and there are water drops in the pipe.

7.50 years life test: geothermal pipe in the national chemical building materials test center inspection test, test conditions: 110 degrees, 2.8Mpa (MPa) hydraulic test, passed 8760 hours (365 × 24, one year) as qualified, in the sealed conditions are not seen Light is carried out. According to the pipe life curve of the HVAC industry, it is found from the table that under normal heating conditions of 70 degrees water temperature and 0.4Mpa (4 atmospheres), the service life is about 500,000 hours (more than 50 years). Irradiation, sunlight will accelerate aging, shorten the service life, avoiding light can slow down the aging of plastic products, and prolong the life, which is one of the reasons for the heat pipe and the light shield before the water separator.

On the other hand, the reason is to avoid the generation of algae and green moss when the light is stopped in summer, causing embolism or blockage of the pipeline.

4. Characteristics of PE-RT and PEX-A geothermal pipes

1).PE-RT: The pipe has no bending memory, can be hot melted, has high thermal creep, good low temperature and good brittleness, expensive raw materials and easy control of production process. PEX-A: The pipe has bending memory, can not be hot-melt connected, has less thermal creep, low temperature and low brittle resistance, cheaper raw materials, and difficult to control the production process.

2). PEX-A and PE-RT construction PE-RT geothermal pipe has no bending memory, low temperature and good brittleness, and can be preheated and bent without bending. Convenient construction. The PEX-A tube has bending memory and low temperature and low brittle resistance. It is not allowed to preheat and bend the tube at low temperature. Construction is cumbersome.

3).PEX-A and PE-RT geothermal pipes are connected to the water separator. PEX-A is a card type connection time with water seepage. PE-RT is a hot melt connection. PEX-A geothermal pipe card connection is avoided. The water seepage situation.

4). PEX-A and PE-RT geothermal pipe maintenance PEX-A pipe can not be hot-melt connection if the problem (breaking pipe) can not be repaired, and PE-RT pipe can be hot-melt connection if the problem (breaking pipe) can be repaired, Moreover, the construction is convenient and the process is simple.

5). PEX-A and PE-RT geothermal pipe protection PEX-A can not be recycled, not environmentally friendly. PE-RT is a waste material produced by thermoplastic raw materials during production or use, which can be recycled without polluting the environment.

(2) Insulation materials

1. Polystyrene insulation board (EPS) national standard requirements (volume weight) 20KG/m3 or more, thickness 20MM, low thermal conductivity, low water absorption, usually not reached in the market, 17-18KG/ Cubic meters, the thickness of 15-17MM is good, (increased cost of about 40 yuan per cubic meter per cubic meter) dealers report that the quality is too good, but the sales are not good; the density is too low, if the bean concrete cover is too thin, time If the local load is too large, it will easily cause collapse (Dalian has reported such incidents), because geothermal heating requires leg bedding, furniture, and does not affect the heat dissipation effect.

2, extruded polystyrene insulation board (XPS) capacity is greater than 42KG / cubic meters, extruded, brittle, suitable for ground leveling geothermal paving, high cost. Flame retardant materials should be selected for both.

3. Geothermal cotton should be a sound-insulating material for air-conditioning installation. The thermal conductivity is high. It is not recommended. However, bathing places and other places that require a shorter period of time, or own homes, the attic, the upper level of the villa.

(three), iron mesh

The iron mesh size on the market is 1M×2M iron mesh wire diameter is divided into 1.5MM, 1.6MM, 1.7MM, 1.8MM.2.0MM, 2.3MM, 2.8MM and so on.

A. It is convenient to fix the pipe, make the pipe spacing more uniform and more straight. B. Disperse the deformed stress of the backfilled bean concrete, reduce the crack on the ground, protect the insulation layer from collapsing, play the skeleton role of the concrete, and the iron wire is thicker. The network is better.

(four), radiation film

The substrate is made of non-woven fabric, and the paper quality is poor. It is easy to be damaged by moisture when it is made of pea stone concrete floor; the pure aluminum foil is good, and the chemical vacuum coating is worse.

(5), water separator

Can be divided into temperature control type that can automatically control the temperature, ordinary copper, stainless steel, PPR, etc., commonly used is a common copper water separator.

Should pass the identification:

Sealing test: 1.6 MPa, no leakage for 30 seconds; pressure test: 95 degrees, 2.5 MPa, 1 hour, no leakage deformation, the main copper body has no trachoma, the wall thickness is some, and even, each branch The road interval is larger, which is convenient for future maintenance;

The branch valve on the water separator, the valve core is good for copper nickel plating, not easy to corrode; in addition, the joint of the geothermal tube and the water separator is easy to aging, the life is short, and the direct copper piece The life of the link is long.

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