Contd. from Part-I….
Camber or sweep (where necessary), dimensions, layout etc. are checked as per fabrication & erection drawings.
Priming & painting of structural steel members are examined as per relevant guidelines. Dry film thickness of paint coats may be checked with ELCO meter.
Fabricated structural members are well identified with erection marks in order to ensure smooth & correct erection. Centreline and elevation marking of members to be erected are also very much parts of erection procedure.
Quality of bolts, nuts, washers etc. should conform to relevant quality documents. Dimensions of holes, pitch distance & diagonals of bolts, tightening of bolts etc. need careful observation.
Verticality of columns or suchlike, various dimensional checks of structural members as well as those of layouts are necessary. Fabrication & erection tolerances are usually well laid down in various quality assurance documents such as, codes, contract specifications etc.
Proper care needs to be taken while grouting base plates in columns, trestle foundations as grouting connects the superstructure to it’s foundation rendering it monolithic. Hence, no air pockets must remain inside the finished grout.
Where packer plates are necessary, these are locked by tack welding for which visual inspection is sufficient.
NDT requirement of fillet welds is usually DPT. For butt welds, besides DPT and careful visual inspections, other NDTs like ultrasonic or radiography tests and X-ray test are also performed as & where prescribed in QA guidelines. Usually, contract specifications over and above the concerned codes, prescribes clear guidelines on procedure & acceptance criteria for NDTs, including frequency of such tests.
Preheating and post-welding heat treatments are performed, wherever necessary, as per contract specifications or other relevant quality documents. Structural steel members of certain thicknesses are usually subjected to these treatments as prescribed.
As already mentioned, welding, electrodes etc. itself are extensive subjects and persons with relevant qualification, sufficient knowledge or experience would be aware of much more detail on it. The points briefly discussed above are just some of the many important aspects of the subject matter posted with a view of providing a quick macro-level or general idea.