Fabric expansion joints are flexible connections, which have the scope to absorb expansions, mechanical vibrations and movements of the system in which they are installed.
Made of special textile fibers, completely asbestos free, the fabric expansion joints are designed and produced with several composite layers of different fabrics, in order to meet the specific project requests.
Usually, fabric expansion joints are produced in three configurations:
- horizontal flanges;
- vertical flanges;
- sleeves.
In addition, they can be supplied closed or open, with or without holes, in circular, rectangular or truncated cone execution or in special shapes requested by the customer.
They can be used in a wide variety of ways and offer a number of advantages, firstly they do not generate pressure on the pipes where they are installed.
In addition, the fabric expansion joints can be supplied with internal bolster bags, which have the scope of:
– protecting the expansion joint from dust and/or ash;
– supporting the expansion joint in case of strong vibrations of the pipe caused by pulsating pressures;
– reducing the surface temperature.
Actually, the installation of a bolster bag, has the advantage of reducing the thermal stress on the expansion joint, extending its life.
In addition, bolster bags, due to the good sound-absorbing properties of the materials used, act as an acoustic barrier, thus reducing noise.
The materials which compose fabric expansion joints
Each layer that makes up the fabric expansion joint is chosen for a specific purpose and is positioned in the layering assembly, so that it can operate at temperatures below its limit working temperature.
We can divide the layers into different categories; let’s see them in detail.
– Containment layer: this is the inner layer in contact with the fluid, generally consisting of a rough fabric, in glass fibre or silica. It is sometimes laminated to a wire cloth to increase its resistance to abrasion.
– Sealing layer: this is the outer layer in contact with the environment. Its purpose is to guarantee the gas tightness of the entire layer. It consists of glass fibre fabrics “impregnated/coated” with suitable materials such as silicone or PTFE.
– Acid barrier layer: this is the layer that has the task of containing and protecting the sealing layers from possible acid attacks, preventing damage and consequent gas leakage. It is made of PTFE.
– Thermal abatement layer: this is the layer necessary to abate the temperature, so that the outer layers (acid barrier and sealing fabric) can work at suitable temperatures, guaranteeing an adequate surface temperature of the joint. It generally consists of glass, silica or ecological ceramic felts.
– External protection layer: this is an additional layer, not always present, which has the purpose of protecting the fabric expansion joint from external mechanical actions, such as contact with metal elements or other joints. It generally consists of a fibre fabric.
Over the years there has been an evolution in the fabrics used to realize expansion joints, in particular those which are part of the category of sealing layers.
The most used fabrics can be divided as follows:
– Fibre fabrics with a silicone coating, suitable for air or mildly aggressive fumes. In this case they must be combined with an acid barrier. The maximum ambient temperature at which they can operate is 180°C.
– PTFE impregnated fibre fabrics, suitable for aggressive fumes. They are always coupled with an acid barrier. The maximum ambient temperature at which they can operate is 300°C.
– PTFE laminated and impregnated fibre fabrics, suitable for acidic fumes with condensation. They do not need an acid barrier because it is incorporated in the fabric itself, through lamination, which can be uni or multidirectional. The maximum ambient temperature they can operate a is 315°C.
There are other types, such as PVC, Hypalon or metal foils, which are used for specific applications.
The importance of a supervision in your plants
From what we have said so far, it is clear that fabric expansion joints are not all the same, but adapt to the needs of the customer and the system in which they are installed.
For this reason, it is important not to underestimate their composition and state of wear, as they play a decisive role in the proper working of your system.
You should periodically submit the piping systems of your installations to a deep analysis.
To have a control or a thermal analysis carried out by thermography of the expansion joints is important to understand whether the whole system is working properly.
Fabric expansion joints should be replaced or repaired at the first signs of wear. This should not be underestimated: fabric expansion joints are essential not only to ensure the efficiency of a plant, but also to protect the environment and the safety of workers.
Do you want to know how efficient your installations are?
Today you have the opportunity to know a company that offers something different from the usual expansion joints.
New Componit is a company that has been operating for over 30 years in the production of customized products for heat treatment.
The study and continuous research, on materials and production techniques, has allowed us to offer, our customers, high performance and innovative products.
With our customized Efficiency Box® program you will have analysis, design and constant support from our skilled technicians.
We guarantee you:
– efficiency tests;
– dedicated specialized team;
– after-sales service and periodic supervision;
– certifications and guarantees.
By also offering a repair and maintenance service, New Componit enables you to reduce the expensive downtime of your plant.
Would you like to know something more about our Efficiency Box® program?
Tommaso Gatto – Export Manager
