PPR pipe winter use precautions

The weather has turned cold and the temperature has dropped. According to the market feedback in previous years, this period is a high incidence of accidents in the PP-R water supply pipeline. When the temperature of the PP-R water supply pipe is lowered, there must be low temperature brittle transition, toughness and resistance. The impact has been reduced, and it gradually shows obvious brittleness at around 0 °C. Once it is subjected to external force, it is easy to break the PPR pipe.

How to distinguish good PP-R tube

1. Isn't the bad pipe a good pipe? ?

This method of judgment is wrong.

Whether it can crack the PP-R tube, this is a misunderstanding to judge the quality of PP-R. This does not test whether PP-R is good or bad, because the performance of PP-R material itself will occur to some extent with the ambient temperature. change. In the case of low temperatures, especially during winter construction, the flexibility of the pipe at low temperatures is reduced, and the rigidity is enhanced, showing brittleness. Under the action of external force impact or excessive accidental load, the pipe may be cracked straight, which may cause inconvenience to the construction.

In the winter construction, attention should be paid to the low-temperature brittleness of the building water supply polypropylene (PP-R) pipeline, and the corresponding construction plan should be formulated. GB/T50349-2005 has detailed provisions for this. Instead, some fake and inferior PP-R tubes with other raw materials are not easy to break! The true PP-R, which can transport both high-temperature hot water and cold water, can be cleaved for 50 years, especially at lower temperatures. This is the low-temperature brittleness of PP-R. If the PP-R water pipe cannot be split, it can be concluded that it is not a true PP-R material.

The advantages of PP-R tubes are mainly reflected in the high creep resistance. The good tube of pure PPR material has low temperature brittleness, especially in the environment below 5 °C, so the good tube can be split, and the cracking is often not PP-R tube, but PP-B for conveying cold water or It is mixed with other materials.

2. How to distinguish the good and bad of PP-R tube? ?

1 look - whether the surface and cut surface have oily texture!

When observing PPR products with the naked eye, it is necessary not only to look at the surface work of the product, but more importantly, to look at the work surface of the product. Good product list is like one!

2 touch - smooth surface and inner wall, no bump!

Good products can talk on their own. When you touch the product, in addition to feeling the outside, the inner wall has a greater impact on the process! Smooth inner walls will greatly reduce water flow resistance!

3 burning - carbon dioxide and water vapor after combustion

We don't need to burn the whole tube! Only a small cut surface can be verified. Of course, you can feel it when you are hot-melting. Good product has a good feeling of melting and no smell! The smell produced must be a product with impurities added. 

3. What is low temperature brittleness?

Answer: The impact absorption energy of materials (all materials, including metal materials and non-metal materials) decreases with decreasing temperature. When the test temperature is lower than Tk (critical transition temperature of ductile and brittle), the impact absorption work decreases significantly, and the material is in a tough state. It becomes a brittle state, which is called low temperature brittleness.

4. Why does the PP-R tube have low temperature brittleness?

Answer: PP-R is a random copolymerized polypropylene obtained by random copolymerization of propylene monomer and a small amount of ethylene monomer under the action of heating, pressurization and catalyst. The ethylene monomers are randomly distributed into the long chain of propylene, wherein the ethylene monomer is generally controlled between 3-5%. The ethylene content and the way in which ethylene and propylene are polymerized determine its cold-brittle character.

In the case of low temperatures, especially during winter construction, the flexibility of the pipe at low temperatures is reduced, and the rigidity is enhanced, showing brittleness. Under the action of external force impact or excessive accidental load, the pipe may be cracked straight, which may cause inconvenience to the construction. To this end, the relevant national regulations have made clear requirements for this issue. In the winter construction, attention should be paid to the low-temperature brittleness of the building water supply polypropylene (PP-R) pipeline, and the corresponding construction plan should be formulated.

5. The form of PP-R pipe cold brittleness in practical application

Answer: When the ambient temperature is low, the toughness of PP-R pipe is reduced and it is brittle. When the pipe is subjected to external force impact or heavy pressure, linear cracking will occur, and the cracking will start from the inner pipe and extend to the outer pipe. . After the pipe is cracked by the force of a point, in a moment, the crack will increase rapidly along the axis of the pipe. This characteristic is called rapid crack growth. In addition, the winter pipe is damaged by external force during transportation, construction and installation, and will appear in the process of brittleness and toughness (when hot water is delivered).

PPR pipe winter use precautions

First, before the pipe is used

1. Strictly regulate the handling, transportation, loading and unloading management of products, and there must be no throwing, falling, rolling or dragging to prevent damage to the products. In particular, it must be handled lightly during the unloading process. After transporting to the construction site, it should be properly kept to prevent the pipe from rubbing against sharp objects. Personnel must not step on the pipe. The above behavior will cause cracks and internal injuries in the inner wall of the pipe. When there is pressure, there will be multiple bursts.

5米。 The pipe is required to be stored in the warehouse and the shed, and the stacking height can not exceed 1. 5m.

3. When the PP-R pipe is transported from the warehouse to the indoor construction site, if the warehouse temperature is lower than the indoor construction temperature, the pipe temperature should be naturally raised to the indoor temperature and then constructed. Special attention should be paid to large diameter PP-R pipes.

Second, the pipe construction

1. The product should be inspected before use. If the abnormality of the pipeline product is found, it should be removed before use. When cutting the pipe with scissors, the scissors should be perpendicular to the axis of the pipe, and press the scissors handle evenly, and avoid breaking the pipe. The end of the pipe may be dark-impacted due to collision when the pipe is handled. It is recommended that the end be cut to a length of about 4-5 cm before joining.

2, according to the design, choose the right pressure of the pipeline

3. The true PPR has poor impact resistance under low temperature conditions (below 5 °C), and it is easy to generate stress concentration or crack under the action of external force, so collision, throwing and mechanical compression should be avoided in pipe construction.

4. The PPR pipe and the piece are inserted into the heating mold, and the pipe and the pipe are heated and the insertion process is not allowed to rotate. Especially in low temperature environments, it should be avoided.

5, pay attention to control the pipe, and the pipe fittings absorb heat to prevent temperature differences.

6. Pay attention to controlling the heating time so that the pipe fittings are enough to absorb heat to reach the optimum melting point (260±10 °C). When the pipe is heated, if the ambient temperature is low, the time can be extended appropriately. The welding hot-melt socket depth mark is accurate, and the pipe is required to be inserted into the specified mark without rotation.

7. The plugging time should be fast enough to prevent temperature differences or to reach the optimum melting point.

8. During the processing time, the just-connected joint can be corrected, but rotation is prohibited.

Third, the pipeline pressure test

1. After the pipeline installation is completed, the water to be welded is completely cooled and then tested. The length of the test pipeline is preferably 500m. It is forbidden to carry out water test operation under low temperature conditions. When the pipeline is pressure tested, it is necessary to ensure that the water temperature in the pipeline is equal to the ground temperature at that time, to prevent the pressure of the pipeline from being affected due to the temperature difference, and the pressure test shall not be used.

2. Install the exhaust valve at the water inlet, outlet, and the highest point. When testing, first open the exhaust valve before filling, then slowly fill the water. After the water valve has a water column evenly flowing out, turn down from low to high. When pressurizing to 0.2-0.3Mpa, perform multiple exhausts again, remove all residual air, and then boost to the specified pressure value and then stabilize the pressure gauge for 1 hour. No pressure drop or depressurization range is 0.05. Within the Mpa is qualified.

Fourth, after the pipeline is installed

1. Finish the pipeline after the completion of the pipeline construction, prohibit collision, crushing, knocking, and make warning signs to remind the construction personnel.

2. The depth of the PP-R water supply pipe buried in the outdoor ground shall not be less than the depth of the frozen line. When the outdoor clearing is laid, and the indoor ice may be frozen, insulation measures shall be taken to ensure that the pipe will not be damaged due to icing.

3, the surface of the pipeline should pay attention to the marking code of the pipe code, "unknown" pipe should not be used.

4. Long-term uninhabited houses are recommended to close the main valve and drain the remaining water in the pipe to close the window. Prevent pipes from freezing.