Various studies have shown that in many plants the majority of pollution comes from losses that are not controlled or monitored, generally focusing on flanged coupling, valves, etc.  These losses are called fugitive emissions.
In recent years the attention towards the environment has risen considerably and the problem of fugitive emissions has become big.

The natural consequence is that technicians require more efficient and high performance sealing systems. A key element in sealing systems is of course the gasket.
Sealing systems are used for the containment of fluids, gasses or liquids, in a circuit or a plant, to avoid leakage of materials.
The fluids can be non-toxic or toxic.
In the first case there is only one loss in plant efficiency, while in the second case there is also the danger to personnel and the surrounding environment.
The gasket is a deformable element made with different materials which, secured between two pieces (the flanges), limits and prevents fluid loss. This action is carried out by establishing a tensional state, generated by a prior deformation that occurs in the tightening phase.

One of the features of a gasket is its deformability in that it makes up for the superficial imperfections and any differences in tolerance of the elements that come into contact.
The pressure generated by the tensional state on the gasket must be sufficiently high in order to eliminate the inevitable defects in the coupling system.

We can combine these imperfections essentially in two groups:
• Micro defects relating generally to coupling imperfections such as: distortion of the flange, non-parallelism, etc.
• Macro defects which instead affect the finishing of coupling surfaces, such as: scratches, carvings, etc.

One discourse on hand and of particular interest is instead done on machining made to obtain the degree of finishing on the surface of flanges.
The roughness of the flanges is a basic parameter that should be taken into consideration for calculating the size of the seal and tightening forces, the higher surface roughness and the value of flexibility required of the gasket as well as the strength of tightening force.

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