TWI Bulletin, July - August 2009
Case study: Enhanced fatigue performance achieved by locally thickened and machined pipe ends - the V&M Tubes solution using Premium Upset Riser End 'PURE'
Minimising the mismatch on assembly with conventional pipe ends can be a time consuming and costly job. Poorly matching pipe ends are invariably responsible for unpredictable fatigue performance in girth welds.
By locally thickening and machining the ends of the pipe, the need for pre-matching of pipe ends is greatly reduced, and improves the weld's fatigue performance.
V&M Tubes Germany commissioned TWI to evaluate the mechanical properties and fatigue performance of girth welds, made using locally thickened and machined pipe ends, so that it could compare these with the performance of girth welds on standard plain pipe ends.
The objectives set were five-fold. TWI was commissioned to;
- Make a number of girth welds on plain end pipe of 273mm outside diameter and 28mm wall thickness
- Make a similar number of welds on pipe ends which have been locally thickened from 28mm to 32mm wall thickness and subsequently machined
- Inspect the girth welds using specified non-destructive techniques
- Carry out mechanical testing of girth welds in both types of pipes
- Perform full scale resonance fatigue testing of a selected number of welded pipe assemblies from each category
From the results it was possible to conclude that the girth welds produced using locally thickened and machined pipe ends performed better in fatigue than those welds produced on plain pipe ends.
