Marking of plastic pipes. Pipes based on polyethylene

Polymers quickly entered our life. In any area of life, you will find many plastic products. Engineering systems are no exception. For heating and water supply systems, there are many varieties of plastic pipes, fittings and other products.

One big category is polyethylene pipes for heating. There are many manufacturers, brands and types on the market. For many people it is difficult to understand who is better and what the difference between them. One of the easiest ways is to read what's written on them. Earlier I've already wrote about the marking of ball valves and polypropylene fittings. In this article, I will show you what the marking of pipes based on polyethylene means.

Pict.1 PEX pipes

All inscriptions on pipes PEX, PERT or metal-plastic can be divided into categories. The main more than ten. So, let's begin.

1. Name, brand

     Here everything is clear. Often the name is highlighted in bold or logo. Sometimes they are simply separated by signs (see pict. 2).

Pict.2 Brands

2. What material used and from which layers does the pipe consist?

    Such pipes can be divided into two main tubes - homogeneous and metal-plastic.

There are several types of material for the manufacture of pipes for heating: 

- Cross-linked polyethylene. It is marked with three letters PEX. It is obtained from conventional polyethylene by a "cross-linking" process. Depending on the type of process, it has an additional marking: a, b or c. Therefore, often on the pipe you can see the following inscriptions: PE-Xa, PE-Xb, PE-Xc.

- Heat-resistant polyethylene PERT.

I will describe the difference between these species in a separate article.

Pict.3 Material of homogeneous pipes

    A note about the color of the outer layer. The color of the pipe does not affect anything. Initially, the original material is a translucent color. And in the production process it can be painted in any color - pink, blue, gold, etc. It's already someone like it).

    Multilayer pipes predominantly have a white outer layer. The marking here is a bit more complicated. These pipes are five-layered. Only 3 main layers are indicated, starting from the inner one. For example - PEX / AL / PEX or PE-RT / AL / PE-HD. The middle layer is made of aluminum. It can be of different thicknesses. Some brands in the marking indicate this value - PEXb / AL0,3 / PEXb (see pict. 4). That is, the thickness of the metal is 0.3 mm.

Pict.4 Marking of layers of multilayer pipes

   If you carefully looked at pict. 4, you could see that on some pipes there are other materials in the marking - PE-HD and PE. They are not heat-resistant materials, because such pipes recommended for use in low-temperature heating systems or cold water.

3. The presence of an "oxygen" barrier

   In one of the previous articles, I told why the presence of oxygen has a negative effect on heating systems. In order to avoid the ingress of gases through the wall of the pipe into the water, manufacturers put into their construction an "antidiffusion" layer. In the metal-plastic pipe, this layer has an aluminum layer. In a homogeneous pipe - a layer of ethylene vinyl alcohol EVOH. On the pipe itself, the presence of this layer can be confirmed in different ways: by the inscriptions OXYGEN BARRIER or EVOH. Or mention of the standard DIN4726, (I'll discuss it later). Accordingly, if you do not find such inscriptions, such a pipe should not be used in heating.

Pict.5 Variants of marking the "oxygen" barrier

4. Diameter and wall thickness

    Here everything is simple. Marking 16x2 means that the outer diameter of the pipe is 16 mm, and the wall thickness is 2 mm. The required pipe diameter select by hydraulic calculation and depending on the type of connections.

Pict.6 Diameters and wall thicknesses

5. Pressure and temperature

      On the pipes there can be a marking of the maximum parameters, for example, Tmax = 90 ° C. But to focus on it is not entirely correct. Since the parameters of temperature and pressure are interrelated. Therefore, it is worth paying attention to what class of operation the product belongs to. The inscription "Class 1-4 / 10bar, Class 5 / 8bar" shows the working pressure for the pipe in this or that class. In pict. 8, you can see a table of operating classes.

Pict.7 Pressure and temperature parameters

Pict.8 Pipe exploitation classes

    If the pipe has the largest class 4, this means that it can not be used in high-temperature radiator heating.

6. Standards

    This is the most voluminous and important category. The presence of inscriptions with the names of standards, confirms the quality of the pipe. Below I will list the main ones.

DIN4726 - confirms that the pipe has an oxygen barrier corresponding to the German quality standard DIN4726;

DIN16892 - the quality standard of materials for PEX pipes;

DIN16893 - conformity of the dimensional characteristics of pipes;

DIN 4102 - classification of flammability of building materials of the German Institute of Standards. Mark A1 - 100% non-flammable, B2 - normal flammability, etc.;

MPA BS - compliance with the requirements of the Institute for Testing of Building Materials in Braunschweig in fire safety. 

Pict.9 Marking standards on pipes

EN ISO 21003 - compliance with the quality standard for metal-plastic pipes;

ISO 15875-1: 2003 - quality standard and parameters for PE pipes;

ISO 22391 - quality and parameter standard for PEHT pipes;

SKZ A431, A527, A497 - compliance with the quality standards of the German Polymer Center SKZ;

DVGW DW-8231CN0034 - German certificate, allowing the use of materials for drinking water systems.

Pict.10 Standards

   Also some pipes have badges of different certification centers. For example - French CSTB and Dutch KIWA.

7. Date of production and yardage

   Information inscriptions are the date of manufacture and incisions of the footage. The latter are located along the entire pipe at a distance of 1 m.

Pict.11 Date and time stamp

8. Country of origin

        A lot of "pseudo-European" brands are represented on the Ukrainian market. The products of such companies are often produced in China. And the quality of such pipes can be a big question. The degree of cross-linking, the type of material and even the presence of the oxygen layer - not all these parameters may comply with European norms. Therefore, it is necessary to give preference to goods specifying the country of production. For example, "made in Germany". But not in any way - "Germany Standard" or simply "Germany". The last two markings most likely have nothing to do with Germany. Read carefully! It can also save you from fakes.

One more thing. Sometimes on the pipe you can see "made in EU". This inscription can be found on the products of even famous brands. It means that the products are manufactured in the EU, but not the fact in the country with which you associate this brand. It is possible that the company has built a new plant in a less "status" European power and does not want to advertise it. Whether this leads to deterioration of quality is an unknown issue. This requires only time. But is it worth the risk?

Pict.12 Indication of the country of origin

Now you can easily proceed with the selection of the pipe. If you still have any questions - write in the comments. I will gladly answer them. Good luck!