Essential Parts of Pressure Canners Covers of pressure canners are locked in place so that they cannot be lifted by steam. Most new canners have covers that slide into a locked position. A gauge, whether a dial or weight, is essential to control pressure. The weight type permits pressure to rise to a definite point and then releases excess steam to keep pressure from going higher. With either type, you must adjust the heat to keep the pressure steady.
Gaskets keep steam from leaking out around the cover.
Replace the gasket when it becomes stretched or allows steam to escape. Safety plugs go into action only if pressure or temperature becomes dangerously high. One type of plug melts when pressure gets too high or utensil boils dry. Another type of plug is blown out by excessive pressure. Both types are replaceable.