Valve device

A valve device comprising:

• a valve body having an inflow passage and an outflow passage;
• a valve seat fixed to the valve body at a position between said passages;
• a valve element adapted to seat against and be separable from the valve seat;
• a valve stem movable together with the valve element toward and away from the valve seat;
• a stem holding member of a unitary construction secured at a portion thereof to the valve body in the body interior and holding the valve stem at a screw engagement part therewith, a surface at an extremity of said portion of the stem holding member being in abutting contact with a surface of the valve body thereby to form a first metal-contact seal;
• a bonnet detachably fixed to the valve body and covering the remainder portion of the stem holding member, said valve stem being rotatable within said bonnet, a first sealing member interposed between said bonnet and said valve body, a second sealing member interposed between said bonnet and said valve stem;
• and
• means for forming a second metal-contact seal between the stem and the stem holding member when the valve is in the fully opened state thereof.