Expansion joints are fitted to hoses to absorb dilation caused by changes in temperature, pressure, external movements and the weight of the hose itself.
Studies from reliable sources and years of experience with the product have shown that metal expansion joints are ideal for this purpose as their flexibility absorbs movements in all directions better than other materials, reducing business and manpower costs. They also reduce load loss and thermal dispersion, which is particularly beneficial for large diameter hoses.
For the expansion joint to fully exploit its potential, it has to be selected and designed with great care; Giorgi Engineering has a team of specialized technicians to assist the client to find the best solution.
Expansion joints are classified according to the type of dilation they can absorb:
- spherical angular
- spherical lateral
- axial with eliminated thrust
- universal with eliminated thrust
DESIGN AND CONSTRUCTION
The bellows is a fundamental element of the expansion joint. Welded with a single longitudinal seam, it is formed from stainless steel or alloy steel by a hydraulic or mechanic process. A controlled procedure forms a series of parallel metallic convolutions for maximum flexibility and reliability.
Giorgi Engineering has devised a system of calculation to analyze the stress to which the bellows are subjected, so that they conform perfectly to the client’s specifications.
Materials used in the manufacture of the bellows must be:
• stress resistant
• corrosion resistant
Given these requirements, stainless steel AISI 321 (maximum temperature 800° C) is used for preference. When particularly high temperatures and corrosion values are present, stainless steel AISI 316/316L, or alloys such as lnconel, Incoloy, Hastelloy, Nichel and Monel are used.
|Components of the expansion joint||Material||Max temperature|
|Flanges||ASTM A 105|
P 245 GH
P 335 GH
|Welding ends||ASTM A 106 Gr. B.|
ASTM A 515 Gr. 70
|Brackets and external elements||S 275 JR|
S 355 JR
|Tie rods and nuts||ASTM 193 B7|
ASTM 194 2H
According to the use to which they are put, there are three categories of limit rods:
- tie rods
- used in pretension mounting
- used to buffer the thrust from internal pressure
Giorgi Engineering can produce expansion joints with terminals to be welded and flanged terminals. They are normally constructed from carbonium steel, but stainless steel can be used on request. The standard flanges are perforated according to UNI - ANSI or special norms and are made in the same materials as above.
Conveyors are welded to the interior of the expansion joint to avoid direct contact between bellows and the fluid. They reduce thermal stress, load loss, turbulence and erosion.
Reinforcing rings in carbon steel are used when the bellows is to be subjected to high pressure; as well as equalizing the pressure, the reinforcing rings can serve as blocking devices.
The exterior of the bellows can be covered with a sheet, generally in carbon steel, to protect the corrugations from damage by foreign matter and facilitate the application of insulating materials.