* Strong backs will be welded on one shell after initial alignment. * Took polar readings on either side of the joint & both ends of the Shells * Plotted polar diagrams and checked the eccentricity.
* Tolerances :
* Eccentricity (radial run out ) must not exceed
* +/- 1.0 mm of the inlet & outlet rings
* +/- 1.5mm of the erection welds.
* +/- 1.4mm of kiln section in the live ring.
Axial untruth of live ring must not exceed +/- 1mm
* After completion of alignment, weld the strong backs to the other side. Welding of Joint :
* Clean the joint surface.
* Preheat the joint area of shell ( 1m lg ) to 150 deg
* Welding electrodes are to be preheated
* Complete the root run on the outer surface of the joint side with 2.5mm electrode. * Next with 4mm electrode & then 5mm & 6 mm electrodes. * Gouge & remove the root run weld from the inner surface of the joint, check with Dye penetrant for any cracks and start the root run inside. * Complete the inside welding.
* Check the joint by Ultrasonic testing.
* Importance of Pre-heating:
* Preheating slows the cooling rate in the weld area. This may be necessary to avoid cracking of the weld metal or heat affected zone. * Hydrogen contributes to delayed weld and /or heat affected zone cracking, hence it is important to keep the weld joint free of oil, rust, paint, and moisture as they are sources of hydrogen. * Electrodes used ( 1-2 joint) :
* FLS 9721 : E 7018 (3.15mm ) Bottom runs
* FLS 9721 :...