After lifting the tank with our Retractable jacking system, and a shell plate is place, vertical welds are finished manually or with FCAW welding machine then horizontal external welds using SAW single side Automatic Girth Welding Machine (AGW) machine.(Automatic Girth Welding Machine is to be used for root weld).
To allow space for the Automatic Girth Welding Machine ( AGW Machine) for internal welds all trestles are retracted away from the tank shell after the operating lever on the same power pack is pushed once the lifting lugs and fend off lugs are cut-off after the tank load is release from the jacks once the external welding is completed instead of employing manual welders for internal welds, our method allows maximum utilization of the Automatic Girth Welding Machine ( AGW Machine). To start lifting the next shell, all jack trestles are hydraulically moved back together to their original vertical position after finishing the horizontal internal welding.
These Retractable jacks use lifting hook instead of lifting arm. The hook holds and lifts the tank shell from the base edge of the plate thereby there is no need to weld lifting lugs and fend-off lugs to test and repair tank shell plates once the lugs are removed.
Below is the process of fixing next shell and hook removal:
Root gap is left as required while the tank is lowered down using jacks which are lowered by 70mm without lowering the lifting hooks as new shell ring will obstruct the downward movement.
Gradually the shell plate is wedged towards the front using a crowbar in order to free the lifting hook thereby allowing the hook to drop onto the Retractable jack.