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Specifications
The expansion joints are applied to pipelines, which are altering
their lengths due to changes in temperature and pressure, as well
as to pipe systems, which are subjected to vibrations. There are four
different fields in which the expansion joints can be applied:
Heating systems
Engines
Industry
Power plants
These fields demand expansion joints with superior specifications,
high reliability, quality construction and long life expectancy. Metalloviotechniki
manufactures expansion joints using bellows, which are supplied by
BOA AG.
These bellows consist of many thin stainless steel layers (Drw. 2).
The multi-ply expansion joints, contrary to the single-ply ones (Drw.
1), provide great elasticity, noise reduction and a high degree of
safety in the case of rupture.
Bellow material
The multi-layered bellows are constructed by high-grade chrome-nickel
steel (AISI 321, 316ti), offering a high resistance against aging,
temperature, UV-radiation and most of aggressive media. Upon request
other stainless steel alloys may be used, for example AISI 309, 310
provide resistance to high temperature conditions and Nickel-based
alloy 825 is suitable to resist the sea water corrosion on the bellow.
The end parts of the expansion joints may consist of stainless steel
(AISI 304, 316, 321, 309, 310), of mild steel (St37, St60). or of
many other materials (Cu, Al, Cu-Sn). These materials can be used
for the production of the flanges, whose dimensions are according
to the international standards (DIN, ANSI, JIS) or according to the
customer's request.
For the protection of the bellow and for a smooth flow of the medium,
an internal sleeve should be welded at the expansion joint. This is
recommended wherever the following conditions are to be faced:
Abrasive media
Flow velocity of liquids, u > 3 m/s
Flow velocity of air, steam or gas, u > 7 m/s
Big temperature difference
Types of expansion joints
According to the direction of the bellows movement,
expansion joints can be classified in the following categories:
Axial expansion joints
Angular, hinged expansion joints
Lateral expansion joints
Universal expansion joints (compensation of axial & lateral movement)
Special Expansion joints
Vibration absorbers
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