Since you can install a globe valve with
seat and/or disk surface. When doing this work,
pressure either above the disk or below the disk
you should observe the following precautions:
(depending on which method will be best for the
When refinishing the valve seat, do not re-
operation, protection, maintenance, and repair of
move more material than is necessary. You
the machinery served by the system), you should
can finish valves that do not have replace-
use caution. The question of what would happen
able valve seats only a limited number of
if the disk became detached from the stem is a
times.
major consideration in determining whether
pressure should be above the disk or below it. If
Before doing any repair to the seat and disk
you are required to install a globe valve, be SURE
of a globe valve, check the valve disk to
to check the blueprints for the system to see which
make certain it is secured rigidly to and is
way the valve must be installed. Very serious
square on the valve stem. Also, check to be
casualties can result if a valve is installed with
sure that the stem is straight. If the stem is
pressure above the disk when it should be below
not straight, the valve disk cannot seat
the disk, or below the disk when it should be
properly.
above.
Carefully inspect the valve seat and valve
disk for evidence of wear, for cuts on the
Valves that have been in constant service for a
seating area, and for improper fit of the
long time will eventually require gland tightening,
disk to the seat. Even if the disk and seat
repacking, or a complete overhaul of all parts. If
appear to be in good condition, you should
you know that a valve is not doing the job for
perform a spot-in check to find out
which it was intended, dismantle the valve and
whether they actually are in good
inspect all parts. You must repair or replace all
condition.
defective parts.
Figure 6-15 shows a standard checkoff
The repair of globe valves (other than routine
diagram for performing a routine inspection and
renewal of packing) is limited to refinishing the
minor maintenance of a valve.
Figure 6-15--Valve maintenance checkoff diagram.
6-11
