Carbon steel press-system

In previous article, I talked about types of press fitting systems for metal pipes. It differ in material from which it made - copper, stainless and carbon steel. The latter type is the most economical option. Although it has limited scope. This is due to some technical features. That's about it today and I will tell.

Pict.1 Carbon steel fittings from Frabo (Italy)

Material

Elements of systems made of carbon steel. Depending on the application, factory and type of element, steel grade may be different.

Fittings usually made of next steel grades:

- 1.0225;

- 1.0034;

- 1.0038.

Steel grades that are used to pipes producing:

- 1.0215;

- 1.0220;

- 1.0031;

- 1.0034.

In the bulk of the products for heating systems, manufacturers use steel E195 (1.0034), for fire extinguishing systems (splinkers) - E220. The main differences are in the physical parameters of the material (pls see tab.1):

Tabl.1 Characteristics of different steel grades

Application area

As I wrote above, galvanized steel pipes and fittings have limited scope. It cann’t be used in any combination of materials for drinking water systems and gas supply.

The application area depends on two parameters - pipe coating and material of sealing rings of the fittings.

Pipes

There are three types of galvanized steel pipes:

- galvanized outside;

- galvanized outside and inside;

- with a polymeric covering.

Pict.2 Galvanized steel pipes. From left to right: galvanized on the outside, galvanized on both sides, with polymer coating

The first type of pipe usually use for basic systems: heating, cooling, compressed air, solar systems, etc. Pipes with outside and inside zinc cover - only for fire extinguishing systems (for example, Sanha-Therm DZ pipes). Because when it used in heating systems, for example, inner layer of zinc can flake off and adversely effect of circulation of the coolant and operation of fittings. In addition, the use of antifreeze, ethylene glycol as a coolant only increases likelihood of exfoliation.

The main function of zinc coating is to protect against corrosion. Sometimes there is the likelihood of damage to outer layer of galvanizing. Then you can apply a third type of pipe with a polymer coating (polypropylene). It protects zinc layer from damage. This type of pipe is in the range of Geberit, Viega and Frabo.

The layer of zinc, or more precisely Fe / Zn88, can be different of thickness. The greater the thickness, the less likely it is to be damaged (pls see tab.2).

Table 2. Cover thickness

Seals

For the manufacture of O-rings in system of galvanized fittings, two materials usually use - EPDM (ethylene-propylene-diene-monomer) and Viton (FKM, FPM). For visual identification, seals of different materials are indicated by different colors - EPDM (black), FKM (green, blue, red). Fittings with FKM seals can be used in systems with more aggressive workspace. In addition, it works fine in high-temperature environments (pls see tab.3).

Table 3. Type of seal

As can be seen from table 3, each manufacturer has its own recommendations on use of a particular type of seal. For example, Eurotubi has 3 types in their assortment. For exact selection of fittings it is better to refer to the manufacturer's catalogs.

Pict.3 Seals for fittings from different materials. On the left - EPDM. Right - FKM

Pressing profiles

To connect the fittings and pipes used pressing tool with the "jaws". Type of jaws depends on the fitting profile. Different brands use different types of fittings. The prevailing quantities use two types - M-profile and V-profile. It differ in the location of the O-ring seal.

Pict.4 Fitting profils

I cann’t say which one is better. Much depends on material and right choosing of tool. The only caveat is that the fittings of the M-profile of large sizes are pressed better. Because Viega, for example, have a different extrusion profile for big diameters 76, 89 and 108 (pls see tab.4).

Table 4. Fitting profils of other brands

Security

All companies manufacturing products for this system are concerned about security of system as a whole. At the beginning of use of this product, there were cases when installers simply forget to pressurize the connection. Often this happened when there were very large objects. To avoid this, Geberit came up with a crimp indication system. A plastic ring is put on each fitting from the factory, which disappears when in contact with tool. Accordingly, if you forgot to make a pressure test, the ring will remain, and you will quickly see it (pls see pict. 5).

Pict.5 Process of pressing a fitting with a polyethylene indication ring

Another solution was to change the configuration of the O-ring seal in such a way that, when the connection was not molded, it guaranteed would leak. So there have been cases that even with a minimum pressure, an un-pressed compound worked for a time. So later led to flooding and significant losses. This solution was implemented by many brands: KAN-Therm (LBP system), Viega (SC-Contur), Frabo (SecurFrabo), etc.

Pict.6 O-ring seals of different companies. From left to right: Geberit, Conex Banninger, KAN-Therm

Range

The main assortment consists of dimensions - 15, 18, 22, 28, 35, 42, 54, 76, 89 and 108 mm. For fire protection systems, dimensions start from 22nd diameter.

Sanha, KAN-Therm, Viega, Frabo and Eurotubi also manufacture products with a diameter of 12 mm. There are also intermediate diameters:

- 66.7 mm (Sanha, Geberit, KAN-Therm);

- 64 mm (Viega).

Pipes are supplied in sections of 6 m (less often - 3 meters).

In conclusion, I want to add that the most important thing in choosing a system of carbon steel is not  choice of producer, but definition of products based on the area of ​​application.

In the next article, I will talk about systems of press connections made of stainless steel.