Axial Expansion Joints

Lateral Expansion Joints

Hinged Expansion Joints

Universal Expansion Joints

Gimbal Expansion Joints

Inline Pressure Balanced Expansion Joints

Elbow Pressure Balanced Expansion Joints

Externally Pressurized Expansion Joints

Pump Connector Expansion Joints

Exhaust Gas Bellows Expansion Joints

Rectangular Expansion Joints

Heavy Wall Expansion Joints

Bellow Elements for Expansion Joints

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Externally Pressurized Expansion Joints

Externally Pressurized Expansion Joints with Flange Ends

An externally pressurized expansion joint takes pressure from the outside of the bellows element rather than on the inside as in a conventional expansion joint. In conventional type of expansion joints with internally pressurized bellows it is not possible to accommodate large axial movements due to the squirm associated with the higher bellows length.

The stabilizing effect of the  external pressure increases the bellows capacity to absorb high axial movements without squirm making the externally pressurized expansion joints the best solution for  applications involving very high axial movements.

Fixed Flanges (Type 5101)

Weld Ends (Type 5102)

The construction of an externally pressurised expansion joint consists of  a heavy outer pipe which contains the pressure and serves as a shroud to protect the bellows and also functions as pipe-guide. The outer pipe contains the full pressure of the system and if bellows failure occurs the medium  does not escape radially outwards, thus protecting the personnel working in the vicinity.

The internal pipe of the externally pressurised expansion joint acts as liner and maintains fluid flow external to the bellows so that the flowing medium does not collect inside the bellows convolutions and hence do not attack the bellows element if the flowing medium is corrosive. Drain and vent connections can be easily provided to remove any sediment or residue that collects inside the outer shroud.

The externally pressurised expansion joint is extremely easy to insulate and steam tracing  can be used to maintain the temperature of the medium flowing through it. Another important advantage of this type of expansion joint is that in the event of anchor failure the bellows get compressed and act as a shock absorber to maintain the overall system stability.

Fixed Flanges Weld Ends (Type 5103)

Fixed Flanges Double Bellows With Anchor Base (Type 5104)

The externally pressurised expansion joints provide very low turbulence to the flowing medium due to the fact that the internal surface of the pipeline itself works as the liner for this expansion joint. As the thermal expansion occurs the bellows element gets extended bringing the internal guide rings closer reducing the gap between them and the medium can flow through this joint as if it were not there.

The drain vent and purge connection can be provided in the outer pipe to allow the draining of any sediment or residue that may collect or venting of the expansion joint to assure fluid filled pipeline. The drain connection is also an ideal location  for a steam trap for joints used in steam applications.

WORKING OF AN EXTERNALLY PRESSURIZED EXPANSION JOINT

Fluid enters the unit through pipe 1 and leaves the unit through pipe 4 . the fluid completely fills the outer pipe 2 and pressurizes the outside of the bellows 3. The pressure inside the shroud acts external to the bellows , keeps the long bellows from bucking and thus avoids squirm. The outer pipe2 functions as a shroud to protect the bellows and guides the movement of the expansion joint  in combination with the guide ring 5 and 6

As the pipe extends due to thermal expansion the bellows element gets extended  as shown. The seal weld at each end of the bellows prevents any leakage from the pressurized area. The externally pressurised expansion joint offers all the advantages of a slip type expansion joint and since it is packless without any gland-packing  it is totally maintenance free as compared to slip type expansion joints.

And since its is totally maintenance free it can be installed in areas where accessibility is limited. Also since there are no sliding parts there is no need of lubrication or repacking.

INSTALLATION  OF AN EXTERNALLY PRESSURIZED EXPANSION JOINT

The single externally pressurised expansion joint is normally located near an anchor at one end of the long piping run. This joint should  be installed with the fixed end adjacent to the anchor.

The double universal expansion joint  which is essentially an assembly of two single joints mounted back to back connected by a common casing is installed at the centre of the long piping run. This type of double externally pressurised expansion joint is provided with a support foot which acts as an intermediate anchor.

Weld Ends Double Bellows With Anchor Base (Type 5105)