Dual seal for shut-off valve

摘要

A two stage seal for a shut-off valve having a bonnet with a rotatable valve stem therethrough. The first seal is conventional packing material axially compressible to adjust its sealing force against the valve stem. The second is a cartridge seal gland with inner and outer "O" rings axially biased against the packing material by a packing nut threaded in the bonnet.