I need to find out the typical welding pressure required to weld 1.5mm hot rolled steel. I am looking at adding individual flow controls to guns. Currently I have no way to control individual gun closing force. Plant air is at 100psi, I regulate air going into the machine at 80psi, all 8 guns are at this pressure. Individual guns range from 750 to 1220 lbf. We are having big problems cracking adapters, I believe it is because we are running at too high of pressure. We are welding at approx 15 cycles, 1 -4 welds per gun per cylce, approx 1200 cycles per day. Guns are made by Savair.