General information

  • Metal expansion joints are flexible corrugated „bellows“ manufactured by forming of metal plates from wide range of steels – stainless also carbon. Could have circulare, or non-circular section, metal expansion joints are manufactured with welding ends, or flanges and for small dimensions also with threaded fittings.
  • Metal expansion joints with circular section are manufactured from dimension DN 15 up to DN 5000 mm.
  • Metal expansion joints with non-circular (rectangular section) are manufactured according to individual requirements of customer.

Use of expansion joints

Metal expansion joints are intended for elimination of thermal dilatation in pipelines with variable temperature (hot water, steam, exhaust gas), absorbing of mechanical vibrations from the pulsating aggregates (pumps, compressors, combustion engines, ...), elimination of mounting uncertainties and other operational movements of piping systems.

Basic dividing of expansion joints

Expansion joints are divided according to method of stress:

                     
AXIAL             ANGULAR             LATERAL             VIBRATION ABSORBER
     

Thermal resistance

For metal expansion joints in standard material version is from – 196°C up to 600°C. It could be higher in case of use a special materials.

Pressure resistance

For metal expansion joints it depends on dimension of expansion joint, construction of corrugated bellows and working temperature. Standardly is from -0,1 MPa up to +6,3 MPa.

Construction

Bellows could be manufactured from one layer of metal plate (monolithic) or from more layers of metal plates (multilayer).


Monolithic bellows                 Multilayer bellows
Monolitný vlnovec   Viacvrstvový vlnovec


The advantage of multilayer expansion joints is:
  • lower stiffness, what has positive impact on loading of fixed points,
  • better ability to absorb bigger deflections at smaller assembly dimensions,
  • higher flexibilty at bigger pressure load,
  • ability to absorb mechanical vibrations,
  • possibility of expansion joint manufacture with ineer layer from special steel (Inconel, Incoloy, Titan, ...) for chemically aggressive medium
All bellows are designed, manufactured and tested according to standard EJMA (Expansion Joints Manufacturers Association).

For stability increase of corrugated bellows, to reduce turbulence of flowing medium, or to incease resistance against abrasive parts could be expansion joints manufactured with inner pipe. This is also recommended in case, that velocity flow of liquid medium is more than 3m/s and gaseousmedium is more than 7m/s.

Material of expansion joints

Metal expansion joints are manufactured from following materials, depending on working conditions:
  1. BELLOWS
    standard – AISI 321, AISI 316 Ti
    special – Inconel 625, Incoloy 825, Monel 400, Titan, ...
     
  2. CONNECTION ARMATURES
    good welded steel class 11, 12 and 17, or other according to working conditions
     
  3. INSIDE INNER PIPE
    standard AISI 304