Analyze the comprehensive performance advantages of butt welded aluminum-plastic pipes from national standards

In 2003, my country promulgated and implemented the national standard for aluminum-plastic  composite pressure  pipe:  GB/T18997.1 (aluminum-plastic 

composite pressure pipe part 1: aluminum pipe lap welded aluminum-plastic pipe) and GB/T18997.2 (aluminum-plastic composite pressure pipe) Composite 

pressure pipe part 2: aluminum pipe butt welded aluminum-plastic pipe). According to the above-mentioned national series of standards, aluminum-plastic 

composite pressure pipes are divided into lap welded aluminum-plastic pipes and butt-welded aluminum-plastic pipes. However,   most of the aluminum-

plastic composite pipe products in the domestic market are lap welded aluminum-plastic pipes. People are concerned about butt-welded aluminum-plastic 

pipes produced by a few manufacturers such as Vispert with better performance and higher safety. Little knowledge. This article introduces the comprehen-

sive performance advantages of butt-welded aluminum-plastic pipes from the comparative analysis of the relevant parameters of the national standards for 

lapwelded aluminum-plastic pipes and butt-welded aluminum-plastic pipes.

 　　 1. The difference in wall thickness makes the butt welded aluminum-plastic pipe more characteristic of metal pipe

 It can be seen from the national standard that the total wall thickness of the plastic layer and aluminum layer of butt-welded aluminum-plastic pipes is signi-

ficantly greater than that of lap-welded aluminum-plastic pipes. The thickness of the aluminum layer is particularly obvious (see Table 1), and the thickness is 

increased by 1.5-2.1 times. Table 1 Thickness comparison table

When the composite pipe is under internal pressure, the stress of various materials is distributed according to the elastic modulus of the material, and the 

material with a large elastic modulus bears a larger stress, because the elastic modulus of aluminum strip is dozens of times that of plastic Therefore, thebe-

aring capacity of the aluminum layer determines the bearing capacity of the composite pipe.  The thicker the aluminum layer,  the  stronger  the  bearing ca-

pacity of the composite pipe, and the closer the characteristics of the composite pipe are to the metal pipe. Therefore, butt-welded aluminum-plastic pipe 

can be understood as a metal pipe with a plastic protective layer. From the long-term performance of the pipe, butt-welded aluminum-plastic pipe is safer 

and more reliable.

 　　 2. With pressure-time curve, long-term safety is guaranteed

It can be seen from the standard that the butt-welded aluminum-plastic pipe has a stress-time curve, so that the long-term safe use of the pipe has a reliable 

theoretical and experimental basis. There is no stress-time curve for lap welded aluminum-plastic pipes.In addition, in the butt-welded aluminum-plastic pipe 

stress-time curve, even at 95℃, the curve has no inflection point at all, while other plastic pipe stress-time curves have inflection points. This is one of the but-

twelded aluminum-plastic pipes and other plastic pipes. The important difference is also a significant sign that the butt-welded aluminum-plastic pipe has the 

characteristics of a metal pipe.

 　　 3, high pressure, more high temperature resistance

Table 2 is the comparison data of the maximum long-term working temperature and corresponding working pressure of GB/T18997.1 lap welded aluminum 

plastic pipe and GB/T18997.2 butt welded aluminum plastic pipe. It can be seen that the long-term working temperature of butt-welded aluminum-plastic 

pipe can reach 95℃, and the working pressure can reach 1.25MPa at this temperature. Therefore, the temperature and pressure resistance of butt welded 

aluminum-plastic pipe is obviously better than that of lap welded aluminum-plastic pipe. Table 2 Long-term working temperature and pressure comparison 

table

Even if it is used in 40℃ cold water piping system, the allowable working pressure of lap welded aluminum plastic pipe is only 1.25MPa, while the allowable 

working pressure of butt welded aluminum plastic pipe can reach 2.0MPa. This shows that at low temperatures, butt-welded aluminum-plastic pipes are also 

significantly better than lap-welded aluminum-plastic pipes.

 　　4. High blasting pressure, safer system

Table 3 shows the comparison of the burst pressure of the lap welded aluminum plastic pipe in Table 4 of GB/T18997.1 and the burst pressure of the butt we-

lded aluminum plastic pipe in Table 4 of GB/T18997.2 data. It can be seen from the table that the blasting pressure of butt-welded aluminum-plastic pipes is 

1.33-1.5 times that of lap-welded aluminum-plastic pipes, which means that the safety performance of pipes in actual use is greatly improved, which is partic-

ularly important for current home decoration and middle and high-end projects. . Table 3 Comparison table of burst pressure

 　　 5. The structural characteristics of the pipe make its joints highly reliable

The two types of pipes are obviously different in cross-sectional structure. The thickness of the aluminum layer of the butt-welded aluminum-plastic pipe is 

completely uniform in the circumferential direction, the roundness is easy to ensure, the pipe circumferential rigidity is basically the same, and the sealing su-

rface of the pipe and fittings is connected with uniform stress and deformation in the circumferential direction. Ensure that the joint connection is more relia-

ble and does not leak. The lap welded aluminum-plastic pipe adopts aluminum layer overlap lap welding, the thickness of the aluminum layer is uneven in the 

circumferential direction, and the circumferential stiffness is inconsistent. When the pipe and pipe are connected, the pipe and the sealing ring receive uneven 

circumferential force and deformation. The requirement is higher than that of butt welding aluminum-plastic pipe.

In summary, the butt-welded aluminum-plastic pipe has the advantages of metal pipe characteristics, high working pressure, high temperature resistance, safe 

use, and reliable sealing. Its maximum long-term use temperature is 95℃, and the maximum long-term working pressure is 1.25MPa. Unmatched by other che-

mical building materials. For this reason, after the promulgation of the new national standard, Vispert launched the butt-welded aluminum-plastic pipe that co-

nforms to the new national standard, which was immediately praised and welcomed by new and old users.