I. Introduction:

　　Today, new types of water supply pipes are constantly being added to the construction market. PP-R pipes are one. PP-R pipeline is a new type of pipe that has been produced and applied in China in recent years. The formal national standard of this product has not yet come out. Based on their own practical application experience and related information collected, it is compiled into the following for reference by design and related technical personnel.

　　Advantages and disadvantages of PP-R pipeline:

　　PP-R pipe is a new type of energy-saving plastic product with international level in the 1990s. The full name is random copolymer polypropylene pipe. The advantages and disadvantages of installation and use are as follows:

　　A. Advantages:

　　1. It is harmless to human health. It does not react to all ions in water and chemicals in buildings. Compared with metal pipes, it will not embroider and corrode. Physical properties.

　　2. It is a green and sustainable product, and it has no pollution to the environment during production, construction and use. Can be recycled again and again.

　　3. Different from other pipes, the homogeneous hot-melt connection of PP-R pipe is the biggest advantage of this pipe system. The leak rate of the pipe connection is extremely low, no maintenance is required, and visual inspection can be used. The joint is firm and completely free of corrosion.

　　4. Light weight, convenient construction and transportation, which can greatly reduce the labor intensity of workers, and the construction progress is fast.

　　5. 耐热性能好：瞬间使用水温可达95度。长期使用在工作压力不超过0.6Mpa时，水温可达70度。可满足一般生活和生产热水的需要，是一种较理想的热水管材。

　　6. 导热性低：20度时的导热系数为0.23~0.24W/Mk，比钢管和紫铜管小得多。应用于热水或空调供排水，可在管道保温上节省投资。

　　7. 弹性模量较小：因温度变化产生的应力也较小，适合采用嵌墙和地坪面层的直埋暗敷方式。美观高档，潮流所趋。

　　8. 管道阻力小：管道内壁平滑，不结水垢，水头损失小，沿程水头损失比金属管小，局部水头损失也比金属管小。

　　9. 管道的可修补性能：尽显PP-R管热熔的优点，使用PP-R补洞棒对有针眼的管道进行修补，也可切下受损管道更换新的管道。

　　B.缺点：

　　1. 造价较高：管材现在随着不断的推广价格已经可以接受，但是管配件的价格还是太高，原因一是模具进口;二是管配件中使用的铜和不锈钢配件材料是特制的，要求这些金属配件的温度变化系数要和PP-R材料的温度变化系数严格一致，现也需国外进口。

　　2. 管材规格少，只有外径20至110毫米管径的产品;配件和阀类种类不齐，有与金属阀门连接不便的问题。

　　3. 刚性和抗冲击性能比金属管道差。

　　4. 线膨胀系数较大，明敷或架空敷设所需管道支吊架较多，影响美观。

　　5. 施工设备先进复杂，施工工艺要求高，对施工人员素质和施工管理的要求高。热熔连接的接头质量和温度、加热时间、接缝压力有关，施工中较易出现偏差。

　　6. 抗紫外线能力差，在阳光的长期照射下容易老化。

　　7. PP-R管属于可燃性材料，所以不得用于消防给水系统。

　　三.PP-R管的设计应用

　　1. 管道的设计按以下几个原则选择：

　　a. 管道的规格和管道的壁厚是对应的，管壁越厚管道的耐压就越高，等级也越高，价格也越高。

　　b. 对于热水系统，水的温度越高需要的管壁越厚。考虑到热水系统的安全性,一般热水管必须选择不小于PN2.0Mpa等级的管道。

　　c. 根据供水的安全性和经济性，选择不同的管道等级。重要使用场合管道等级自然就高。

　　2. 管道敷设方法：

　　a. PP-R管道的敷设方法基本上与传统的金属管道相同，可采用串联(主管分支式)方式布置管道。这种敷设方法较柔性塑料管道(如PEX，PE-AL-PE)可节约大量的材料，经济合理，较符合中国国情。

　　b. 按管道敷设走向，可分为明敷和暗敷二种。其中暗敷方式分直埋和非直埋两种。直埋形式包括：嵌墙敷设和地坪面层内敷设;非直埋形式包括;管道井、吊顶内、装饰板后敷设及地坪架空层敷设。

　　c. PP-R管道最适合暗敷，暗敷应与建筑和结构专业协调，采取相应的防护措施，必须在完成管道敷设后进行试压，验收合格后方能掩埋管道并在墙面或地面明显地标出管道的位置。在土建和二次装修完成后应进行第二次试压，排除PP-R管道被破坏的可能，验收合格后方能正式投入使用。此种二次试压法也适用于其他暗敷管道，本人建议将这种验收方法编入相关的规范中。

　　3. 管道连接方式：

　　a. PP-R管道连接方式有：热熔连接、电熔连接、丝扣连接、法兰连接等,应按不同的施工场合、不同的施工要求合理选择。

　　b. 热熔连接和电熔连接适用于PP-R管材与管件的连接，凡采用直埋布管形式的必须采用熟熔或电熔连接。其中电熔连接施工成本较高，适用于管道的最后连接或不方便使用施工工具的场合。

　　c. 丝扣连接和法兰连接使用于PP-R管与金属管或金属用水器的连接。一般小口径管适宜用丝扣连接;大口径管适宜用法兰连接。在管道拆装较多的场合使用带活接头的丝扣连接或法兰连接。

　　4. 施工机具：

　　Construction equipment: The construction machine of PP-R pipe has a hand-held fuser, a trolley-type fuser, an electric heating transformer transformer controller and supporting heating heads, scissors, cutters, brackets, etc. The hand-held fuser is small and flexible, and is suitable for hot-melt connection of medium and small caliber PP-R pipes. The trolley type fuser has a certain volume and weight, and is suitable for the pre-assembly of the hot-melt connection of large and medium-caliber PP-R pipes, that is, the PP-R pipes and fittings are pre-assembled on the ground according to the requirements of the drawing. Then the pre-assembled pipes are assembled at the pipe routing position. The heating power of hot-melt tools is generally 700-1500W, of which 700-800W tools are suitable for hot-melt PP-R pipes of Ф63mm and below; 1200-1500W tools are suitable for hot-melt pipes of Ф75mm and above. The hot-melt machine is composed of a heating plate (with a temperature control device) and a heating head. The corresponding heating head can be replaced with a soil specification pipe. The heating temperature of the fuser is automatically controlled, generally at 260 ± 10 degrees. Electric hot-melt PP-R pipe fittings are embedded with resistance wires on the socket surface of the pipe. During the construction, the surface of the pipe is cut and inserted into the electric fuse socket with a suitable fit, and then a current is passed through the terminal of the pipe at the specified voltage In time, the resistance wire heats up and welds the pipes and fittings. The role of the electric thermal fusion transformer controller is to change the 220V voltage to 39.5V low voltage and power on according to the preset time. The controller has a microcomputer that can identify the ambient temperature and automatically adjust the heating parameters to ensure different operating environments. Welding quality.

　　5. PP-R pipe support and hanger:

　　a. For the aesthetic requirements of the exposed pipeline network, it is necessary to use dense fixed pipe clamps to restrain the deformation of the pipeline. This can avoid the unsightly "serpentine deformation" and collapse problems common in plastic pipe network systems.

　　b. Pipe support spacing points (mm):

　　Temperature difference pipe diameter (mm)

　　20 25 32 40 50 63 75 90 110

　　20 600 750 900 1000 1200 1400 1500 1600 1800

　　30 600 750 900 1000 1200 1400 1500 1600 1800

　　40 600 700 800 900 1100 1300 1400 1500 1700

　　50 600 700 800 900 1100 1300 1400 1500 1700

　　60 550 650 750 850 1000 1150 1250 1400 1600

　　70 550 600 700 800 950 1050 1150 1250 1400

　　6.PP-R pipeline repair:

　　a. The pipeline is damaged. When the buried pipeline has a pinhole, it can be repaired with a 7mm or 12mm repair heating head and a PP-R hole repair rod. This function can be expanded to plant small tubes on large tubes, which can greatly reduce the number of tees and reduce the cost.

　　b. The damaged pipe can also be cut off and replaced with a new pipe by ordinary heat welding.

　　Four. Problems encountered in the practical application of PP-R pipeline:

　　1. Some brands of PP-R pipe fittings are not uniform, and it is inconvenient to install and use. For example, there are no 50 × 20 and 63 × 20 tees. The manufacturer explains that the difference in pipe diameter of the tees is only one or two. The manufacturing standards of the tees are foreign standards, which are different from the domestic use. For example, a 63 mm pipe leads to a 20 mm branch pipe. It requires 63 × 50 tees to use a few different diameter knots to reach a 20 mm branch pipe, which is expensive and unsightly. If you can use pipe repair technology on large pipes and plant small pipes, then the problem of tees is very ideal.

　　2. There are also some problems with the flange connection of PP-R pipelines and ordinary metal fittings: for example, the pressure relief valve set on PP-R pipelines has problems connecting with ordinary flanges. The flange of the pressure relief valve set and PP- The flanges on the R pipe cannot match because the outer diameter of the metal pipe fittings with the same inner diameter and the PP-R pipe are different (the wall thickness is different), that is, the flange of the PP-R pipe is one larger than that of the metal pipe number. The on-site construction unit couldn't solve it, please ask the PP-R pipeline manufacturer to solve it. The manufacturer specially made some flanges to solve this problem.