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CROSBY SERIES HE ISOFLEX
INSTALLATION, MAINTENANCE AND ADJUSTMENT INSTRUCTIONS
1.a Check ring settings
Spindle (12)
Adjusting bolt (26)
Minimum 'A' dimension
Orifice size
K
K
2
M
M
2
P
2
FIGURE 8 - Minimum allowance dimensions
'A'
Nozzle
When the 'A' Dimension is less than shown
above, the nozzle seat should be remachined.
• Lapping compounds
Experience has proven that three grades of
compound - medium, fine and polish - will
condition almost any damaged valve seat
properly, unless, of course, remachining
to establish the seat contour is necessary.
A medium coarse compound may be used for
fast cutting as a first operation after machining,
if desired.
The lapping compounds shown overleaf, or
their commercial equivalents, are suggested.
SELF-ACTUATED SAFETY VALVES
®
(A)
(B)
Bonnet (17)
inches (mm)
Orifice size
.006 (.152)
K
.006 (.152)
K
2
.006 (.152)
M
.006 (.152)
M
2
.010 (.254)
P
2
When the 'B' Dimension is less than shown
above, the insert should be replaced.
• Lapping procedures
Different individuals have different methods
of lapping valve seats, but certain essential
steps must be taken to get satisfactory results.
The following procedure is suggested for
lapping of valve seats:
- Never lap the disc insert against the
nozzle. Lap each part separately against a
cast iron lapping block of the proper size.
These blocks hold the lapping compound in
their surface pores, but must be recharged
and reconditioned frequently.
Minimum 'B' dimension
inches (mm)
.005 (.127)
.006 (.152)
.007 (.178)
.007 (.178)
.010 (.254)
Insert
'B' min.
after
lapping
- Check the lapping block frequently on a
good lapping block conditioner to make
certain that it is perfectly flat on both sides.
If considerable lapping is required, spread
a thin coat of medium lapping compound on
the block. After lapping with this compound,
lap again with a fine compound using a new
lapping block surface. The first step can be
omitted unless much lapping is called for.
Next, lap again using a polish compound.
- Lap the block against the seat.
Never rotate the block continuously, but use
an oscillating movement.
- When all nicks and marks have
disappeared, remove all the compound from
the block and seat. Apply polish compound
to another block and lap the seat with this.
As the lapping nears completion, only the
compound left in the pores of the block
should be present. This should give a very
smooth finish. If scratches appear, the
cause is probably dirty lapping compound.
These scratches should be removed by
using compound free of foreign material.
- Extreme care should be taken throughout to
make certain that the seats are kept flat.
12
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