One of the most convenient ways to make a connection on a pressure vessel or a pipeline is by making an hole on it but, of course, this will reduce the body strenght in that given point so, to retrieve back the previous parent material performance, the welded connection shall have enough characteristics to transfer some of them to the body. This target is usually reached by the adoption of an increased wall thickness of the connection's tube but, sometimes, it's not sufficient. Then the adoption of self-reinforced connection such as weld-o-lets is the next option but this solution requires a lot of welding material in addition to the cost of the fitting, here the logic solution towards the Reinforcing Pads.
As shown in the pictures the reinforcing pads are made by rolled plates oxi-cutted or machined in order to reach the desired dimensions which are defined by proper calculations required by all the Pressure Vessels involved Design Codes, i.e.:
ASME VIII Div.1 UG27
EN 13445-3 Par. 9.4
Due to its particular shape, two welds are required in order to fix it to both the pressure vessel's Body and the Connection, this generate an area between the two which may entrap some weld shielding gas that, being usually composed by corrosive CO2, can be a dangerous threat also in case of Heat Treatments. To avoid this the best practice is to produce two or more holes on the pad's higher surface in order to let the gas evacuate, moreover, these holes will be necessary for HydroTest the whole reinforced area and its relevant welding. It's a recomended good practice to close said holes by means of grub screws as rust prevention.
Non Destructive Examinations (NDE)
Reinforcing Pads Welding are normally subject to Non Destructive Tests by means of Liquid Penetrant test (PT), Magnetic Particle Inspection (MPI) and / or Hydraulic Test (HY) with water or water & soap solution. Click here to visit our N.D.E. Dept.