15-20 minutes. Stewing ribs in a pressure cooker, first cook on high heat for 5 minutes, wait until the pressure cooker makes a snorting sound as well as bubbling, then adjust the high heat to a low simmer for 15 minutes, then turn off the heat, open the pressure cooker when it cools down on its own, add salt and boil over high heat for 3 minutes and then turn off the heat, the total time used is about 15-20 minutes.