Replacement of a failed ‘Elbow Pressure Balanced’ Expansion Joint…

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Bellows Technology have recently completed the re-design and manufacture of 1 off 300mm/12” NB Elbow Pressure Balanced Expansion Joint (see Fig 1 below) for the firewater pump main of an Oil & Gas producing platform in the East Shetland Basin of the Northern North Sea.

The joint was manufactured as a replacement for a failed and leaking joint (see Fig 2 below) on the firewater pump main of the platform. The sea water was leaking from a crack like defect at the lap-fillet welded joint of the upper bellows membrane and the intermediate centre tube.

Having assessed the mode of failure in great detail and following submission of our findings and suggestions for changes to the general construction of the joint, we moved forward to manufacture of the replacement item. Design conditions of 16 Bar at 38 Degrees C prevail with the joint being designed to absorb multi-directional movements.

Key project features:

  • Construction - with the exception of the tie-rod assemblies in 316 stainless steel, all wetted parts were manufactured in Monel 400
  • 300mm/12” NB terminating with an ANSI B16.5 300# RFWN flange at the inlet (elbow) end of the assembly and an ANSI B 16.5 150# RFWN flange at the outlet
  • 16.0 Bar design pressure
  • 100% Radiographic inspection of bellows longitudinal butt-welds, flange to pipe butt welds and end-cap to pipe butt welds
  • 100% DPI of all bellows to pipe attachment welds, tie rod flange to pipe and elbow to pipe welds
  • 24 Bar hydrostatic test pressure held for 30 minutes
  • 2,030mm overall length
  • Movement Specification: +/-5mm axial, +/-4.3mm lateral, -0.11 Degrees angulation
  • Document package containing;

-3.1 material certificates

-Manufacturing drawing

-Certificate of Conformity

-Pressure Test Certificate

-NDT test reports

-Approved weld procedures and qualifications