Using my new R Tech 180 and hobbyweld 5, the 9 l size, and gas has run out before the one job completed. Didn't note actual welding time but calculated that total of 10 feet of weld on mix of 4mm and 5mm box section. Flow rate 10 lpm.which should give 100mins of welding time. In between each welding run, when setting up etc, gas turned off at the bottle. This seems excessive gas use, should I be suspecting internal leak within the welder? All joints tight and no apparent leaks. Previous bottles on Clarke welder lasted much longer.