NIBCO Iron Gate Valves - Manual (Page 4)

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The body and bonnet are bolted together with bolts and nuts; and the joint is sealed with
a non-asbestos gasket. Flow through the valve is stopped by forcing the wedge down
between the seat rings which are screwed into the body. The wedge is the solid type and
is guided through its entire travel by matching guides in the body.
A. RISING STEM OS & Y GATE VALVE
In NIBCO O.S.&Y. rising stem valves, the bottom of the stem screws into the
wedge and is prevented from unscrewing by installing a solid wedge pin. In sizes
14"-24" some designs have an interlocking type stem-wedge connection without
threads or a wedge pin. For the specific valve, this is shown in the appropriate
catalog (5-100).
The wedge is raised and lowered in the waterway by rotating the handwheel
which is attached to the yoke bushing. The handwheel tits onto the hex end of
the yoke bushing and is held on by the handwheel nut which is threaded onto the
top of the yoke bushing. The inside diameter of the yoke bushing has threads
that mate to the upper stem threads. The yoke bushing is held in the top of the
bonnet by the bonnet cap against the rim on the bottom of the yoke bushing. As
the yoke bushing is rotated, the stem and wedge move up and down. The stem
in an O.S.&Y. rising stem gate valve does not turn.
The stuffing box is formed by the circular space between the stem and bonnet
and is filled with non-asbestos packing. The packing is compressed in the
stuffing box by the pack gland bushing and packing gland follower, which are
drawn down against the packing by two gland bolts and nuts. This prevents
leakage between the moveable stem and the stationary bonnet of the valve.
B. NON-RISING STEM GATE VALVE
In NIBCO non-rising stem iron valves, the stem is one piece but has an integral
shoulder on it of a larger diameter than the stem operating diameter. This
shoulder is held in a pocket, in the bonnet when the sniffing box is placed on top
and securely fastened. The stem is operated by the turning of the handwheel.
The threads on the bottom of the stem engage the threads inside the wedge
raising it up and down, when the stem is turned by the handwheel. For non-rising
stem valves, the handwheels fit onto a tapered square end of the stem. The
handwheel is held on by a nut screwed onto threads on the end of the stem.
The stuffing box is formed by the circular space between the stem and bonnet
and is filled with non-asbestos packing. The packing is compressed in the
stuffing box by the pack gland bushing and packing gland follower, which are
drawn down against the packing by two gland bolts and nuts. This prevents
leakage between the moveable stem and the stationary bonnet of the valve.
These bolts have two sets of nuts. The top set is used for adjusting the packing.
The bottom set holds the stuffing box onto the bonnet so it is important not to
loosen or tighten these nuts unless you intend to disassemble or reassemble the
stuffing box from the bonnet.