Nibco Fire Protection Gate Valves User Manual download pdf (Page 4)

NIBCO Technical Services • Phone: 1.888.446.4224 • Fax: 1.888.336.4224

The wedge is raised and lowered in the waterway by rotating the handwheel

which is attached to the yoke bushing. The handwheel fits 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. The

indicator-post flange is held in place with two screws with nuts and seals to

bonnet using gasket.

Resilient-seated valves of this type do not use packing material, but seal the

stem using split, flat rubber-washers. The stem seal is formed by the circular

space between the stem and the indicator-post flange and is sealed with split-

rubber washers. This prevents leakage between the moveable stem and the

stationary bonnet of the valve.

B. NON-RISING STEM GATE VALVE

In the solid wedge or metal seated F-609 Flanged end and M-609 Mechanical

joint 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 captured in a pocket

or counter-bore machined into the bonnet, the stem is secured when the

indicator-post flange is bolted into place. 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.

Since the majority of these valves are either buried or mounted behind walls with

indicator or wall-post assemblies, they do not employ a stuffing box with

conventional packing, but incorporate the placement of two (2) O-ring seals

placed into machined grooves integral to the hub of the indicator-post flange. The

indicator-post flange is bolted and gasketed to the top of the valve bonnet.

Resilient-seated valves of this type also do not use a stuffing box with

conventional packing material, but seal the stem using O-rings. The O-rings are

placed into a gland flange that is separate from the indicator-post flange. The

gland flange also captures the integral stem collar and holds the stem in place.

1 2 3 4 5 6 7 8 9 10

No comments

Nibco Fire Protection Gate Valves User Manual Page 4