C. Lapping Nozzle Seats (Metal Seat,
Non-O-Ring Styles)
ATTENTION!
Nozzle laps as illustrated in Figure 28 are available
from BHGE. Do not use these laps if the valve
nozzle can be removed and machined to the seat
dimensions described in Table 3 and Table 4.
Lap the 5º angle of the nozzle first (Figure 28, View A).
Then, invert the nozzle lap and use the flat side as a
“starter” lap to ensure the seat is square (Figure 28,
View B). Use a ring lap in a circular motion to finish
lapping (See Figure 28, View C and Reconditioning
of Laps). Keep the lap squarely on the flat surface
and avoid rocking the lap, which will cause rounding
of the seat.
D. Lapped Nozzle Seat Widths
A wide nozzle seat will induce leakage, especially
in the smaller-orifice, lower-pressure valves. For this
reason, the seat of valves other than O-Ring valves
should be as narrow as practical. Since the seat must
be wide enough to carry the bearing load imposed
upon it by the pressure force, the higher pressure
valves must have wider seats than the lower pressure
valves. The nozzle seat width should conform to the
measurements in Table 3 and Table 4.
To measure the seat width, use a Model S1-34-35-37
Bausch and Lomb Optical Co. measuring magnifier or
an equivalent seven-power glass with a 3/4” (19.05 mm)
scale showing graduations of 0.005” (0.13 mm). Figure
29a and 29b illustrate the use of this tool in measuring
the nozzle seat width. If additional lighting is required
for measuring, use a gooseneck flashlight similar to the
Type A Lamp Assembly (Standard Molding Corp.), or
equivalent.
XIV. Maintenance Instructions (Contd.)
Nozzle Lap
90˚
85˚
Ring Lap
View A
View C
View B
Nozzle Lap
85˚
90˚
Figure 28: Lapping Nozzle Seats
Figure 29: Measuring Magnifier
Figure 29a: Measuring Magnifier
Measuring
Magnifier
Nozzle
Figure 29b: Magnifier Details
Consolidated 2900 Series POSRV Maintenance Manual
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