A special kind of valve that uses a welded bellows rather than soft packing around the valve stem. The stem of the packless valve does not rotate; it is raised and lowered into the valve body by a connecting stem outside the fluid cavity. Packless or packingless valves usually are for small-diameter piping (one-quarter to 2-inch) and are used on piping carrying hazardous or toxic fluids or gases and for high-pressure steam.
