tfdavid
Materials
- Apr 1, 2010
- 7
Being responsible for parametrizing weldings of fittings to pipelines where there is natural gas flowing in it, I have to calculate the heat input for the beads being made during welding the fitnesses to the pipeline. The heat input HI= V.I/v shouldn´t overpass the maximum value allowable, to prevent risk of burnthrough. There is a document from Shell (DEP 31.38.60.10) which has a graph (appendix 1) displaying the maximum HI for different wall thicknesses and tube diameters. This graph let us calculate the maximum pressure of the pipeline during these weldings by another formula which has the reduced wall thickness due to the welding.
So, I presume that these HI limited values can be a reference for the maximum HI allowable during the weldings, as long as the HI that were generated in the welding procedure qualifications are not overtaken.
But this graph has the HI calculation for only the first beads (butterings, 1st and 2sd fillet welds). What about the remaining fillet welds that are made after? Don´t need to calculate the HI?
So, I presume that these HI limited values can be a reference for the maximum HI allowable during the weldings, as long as the HI that were generated in the welding procedure qualifications are not overtaken.
But this graph has the HI calculation for only the first beads (butterings, 1st and 2sd fillet welds). What about the remaining fillet welds that are made after? Don´t need to calculate the HI?