NIBCO Fire Protection Gate Valves - Manual (Page 6)

NIBCO Technical Services • Phone: 1.888.446.4224 • Fax: 1.888.336.4224
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4.0 TROUBLESHOOTING
Prior to doing any work on any NIBCO valve, it will be necessary to shut down the piping
system, remove pressure and drain, and if necessary, allow cooling and/or
decontaminating before proceeding.
4.1 LEAKAGE THROUGH THE BONNET JOINT
1. Remove the handwheel from the stem.
2. Mark the body – bonnet flanges with a piece of chalk so they can be matched up
later.
3. Remove body-bonnet nuts and bolts.
4. Carefully remove the bonnet assembly. Be careful not to nick or scratch the wedge
seats.
5. Thoroughly clean the body and bonnet joint surfaces.
6. Check the body and bonnet gasket surfaces for any scratches or gouges or other
irregularities.
7. In the even the surfaces are marred, they must be filed or machine flat again. If the
damage is considerable, the body or bonnet may have to be replaced. A competent
valve shop or machine shop may have to be consulted or contact NIBCO Technical
Services or your nearest NIBCO representative for help.
In many cases it is less costly to replace the entire valve rather than have it repaired.
8. With the surfaces now clean and flat again place the gasket on the body and replace
the bonnet. Be careful to use the chalk marks to put everything back together the
same way it came apart. Always use a new clean fresh gasket. It does not pay to
take a chance using the old gasket over again.
9. Reinstall the body-bonnet nuts and bolts, and then carefully check to see that the
body and bonnet are in the same position as when they were separated.
10. Pressure test the valve for leakage to see if a good joint has been made .
4.2 LEAKAGE THROUGH THE STUFFING BOX
Leakage through the stuffing box packing may be stopped by tightening the packing
nut
s . Excessive tightening may cause difficult operation of the valve and could cause
damage to the stem or packing nut. Do not over tighten. The adjustment should be just
tight enough to stop the leak.
If the pack gland follower has run out of travel, isolate and depressurize the valve for
repacking or the addition of more packing.