How to choose the right heat shrinkable sleeve?

"Corrosion protection magazine"

Our article was published in the professional journal “Corrosion protection magazine” in Poland. The article was developed in accordance with the questions of our customers from the Polish and European market. We promote our special properties, such as application on wet epoxy substrate properties at lower temperatures. More information with translation below.

3PE heat shrink sleeves (HSS) is widely used in corrosion protection of welded pipeline connections. According to different installation methods, the main difference lies in the epoxy substrate used, which is divided into a hardened application type called ‘dry’ and a ‘wet’ application type. In recent years, there have been cases of damage to the corrosion protection of the thermal contraction sleeve of 3PE and very low protection parameters in many used and newly built pipelines. Why does the HSS fail? How to choose a heat shrinkable sleeve suitable for a particular project? Below we will discuss the most important issues in connection with the most frequently asked questions from customers and Investors.

1 Why does the thermocoupling belt fail?

Corrosion protection damage is mainly caused by loss of adhesion between the heat shrinkable sleeve and the steel pipe. The installed sleeve loses the function of sealing and shielding the corrosive agent, such as water, causing corrosion of the welded steel pipe connector. The main causes of damage to HSS are in two aspects. One is that the assembly system has insufficient sealing capacity, and the other is an incorrect installation, which leads to the system’s impeccability. The resistance of the HSS to detachment is one of the important factors in evaluating the efficiency of the sealing of the installation system. In the case when the HSS fails, the rupture resistance is almost zero compared to the steel pipe.

3 Why is the strength of the system reduced or lost at low temperature?

Worse parameters at low temperatures are mainly due to the incorrect design of the melting adhesive, among other things, fragility at low temperature. In addition, if the melting adhesive is not strongly attached to the substrate (such as chemical bonding), the internal tension between the materials forming the installation system causes a decrease or loss of abrasion strength at low temperature.

5 How to choose the right sleeve for a specific project?

Usually, the application on a hardened epoxy substrate is suitable only for the use of electric heating through a coil. The wet application system is suitable not only for heating with a burner, but also suitable for electric heating. If the condition of electric heating cannot be met, the application system for wet epoxy which is used at model type HSS 60 or HSS80 from Cheray Polymer is recommended.

2 What is the difference between a hardened epoxy substrate application and a wet application?

The process based on a dry epoxy base refers to the heating and hardening of the substrate prior to the installation of the HSS. To ensure proper properties, the substrate should be heated to very high temperatures often above 100⁰C, most often by induction heating. The substrate is hardened, and then a sleeve is installed. The bonding mechanism is mainly physical bonding and therefore the tearing resistance is very sensitive to temperature. In the case of wet applications, it refers to the installation of a HSS after the application of the substrate, which does not require secondary heating before the strap is laid. In this case, a chemical bond is formed between the epoxy substrate and the melting adhesive layer in the sleeve. The bonding mechanism is mainly chemical and physical bonding, and therefore the tearing resistance is not sensitive to temperature.

4 What if we want to apply an anti-corrosion coating on an active steel pipeline ?

Through the medium in the sleeve with a much lower temperature than the air temperature, a physical phenomenon is created which is the occurrence of a dew point on the steel surface. This effect makes it impossible to use a sleeve on an epoxy substrate here. In this case, the best solution is to use Cheray Polymer type HMS Composite 3C sleeve on the basis of visco-elastic adhesive, which through the application of a special design, obtain the correct sealing parameters regardless of the preparation and preheating of the steel surface.