NIBCO Bronze, Globe and Angle Valves 1/ to Class 175 WWP - Manual (Page 6)

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For water service applications: The flow should enter the valve so that it pushes up
from underneath the seat disc. In other words, water flow should arrive from under the
seat disc and flow smoothly out of the valve over the seat.
After the valve has been installed, the valve should be tested to make sure that it opens
and closes easily and that the bonnet joints or pipe joints are not leaking.
3.0 OPERATION
Globe valves are generally installed to be used for throttling purposes. They normally
have high flow restriction and are not recommended where small pressure drops are
mandatory.
A globe or angle pattern valve must be sized for the specific application, this is very
important. When sizing a globe valve for throttling in either the straight or angle pattern it
is important to avoid tight throttling. A valve sized too large that is tightly throttled can
increase the velocity of the fluid to the point that it can cut (wire draw) through the seat
and/or disc. When the valve is then shut off, it will leak badly.
4.0 TROUBLESHOOTING
4.1
LEAKAGE THROUGH THE BONNET JOINT
If the bonnet joint leaks, the valve should be isolated and depressurized. The bonnet
should be removed according to instructions in Section 5. The seating surfaces of the
bonnet and body should be closely inspected. If there is any scratch or mark on these
surfaces then it is necessary that a flat surface sanding plate of 400 grit be used on the
body to remove all the scratches. After the scratches are removed, blueing should be
applied to a flat plate and put onto the bonnet surface. If there are no high spots on the
bonnet surface, then it is prepared for reassembly. If there are scratches or nicks that
are evident on the bonnet surface, it is necessary that it be indicated in a lathe and a
very slight cut taken off of the bonnet sealing surface at an angle of approximately 2 1/2”
tapered outward with a very fine 32 RMS finish. The two surfaces then can be
reassembled using procedures in Section 2.
4.2
LEAKAGE THROUGH THE STUFFING BOX
Leakage through the stuffing box packing may be stopped by tightening the packing nut.
Water Flow
Steam Flow