January 2014, Vol. 241 No. 1


Erne buttweld fittings allow segmentation during line pipe installation

Line pipe construction often requires abrupt directional changes due to topographic changes in hilly terrain, or because of installation issues occurring in in populated areas.

Another challenge comes in the form of repairs that require an elbow to fit to an existing pipeline segment, often making field segmentation of elbows a necessity. In the case of typical segmentable elbows, common standards (e.g. MSS SP 75) refer to limitations concerning the roundness of an elbow with +/-1%.

However, these limitations do not take into account the tolerances of the nominal diameter of the pipes and the fittings. Using a new high-precision mandrel forming method, Erne Fittings provides elbows, guaranteeing optimum nominal diameters, together with tightest tolerances via the whole body of the fittings after cutting with conventional methods in the field.

This enables the field segmentation of elbows during the installation of line pipes with minimum misalignment between pipe and fitting. This allows for a convenient way to carry out all welding operations without any adjustments of the bevel ends prior to welding. Moreover, the use of pups (small adapter pipes), which are usually used to enable back welding, are not necessary because the root layer can be welded from outside.

The use of these segmentable elbows reduces the necessary number of such pups in line pipes, and, hence, the number of circumferential welds. This increases the efficiency during line pipe construction and substantially reduces construction time and costs.

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