Curtiss-Wright 2600 Series, Maintenance Manual

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8. Maintenance and Repair Procedures
Nozzle Refacing
1. Prior to refacing the nozzle seating area, grip
the nozzle flange in a lathe chuck fitted with
soft jaws (preferably with removable top
jaws), and bored on each set-up to fit the
nozzle flange outside diameter.
2. True up the nozzle by means of an indicator,
ensuring that the nozzle bore and the
machined surface between the nozzle
threads and body sealing surface are
concentric with each other, within 0.002"
full indicator reading.
3. Machine a light cut across the seat until the damaged areas are removed,
ensuring compliance with Appendix E. The seat should be machined to the
smoothest possible finish. Rigidity of the cutting tool is critical.
4. Relap to the required finish.
5. Discard and replace the nozzle when the length from the seat to the
flange becomes less than the minimum specified by the manufacturer.
Do not reduce the nozzle flange thickness in an attempt to maintain the
“L” dimension. The valve center to face dimension will be altered as a
result and nozzle strength may be impaired.
6. See Appendix E for Critical Dimensions.
Disc Refacing
1. Prior to refacing the disc seating area, grip the disc outside diameter in
a universal three-jaw lathe chuck fitted with soft jaws (preferably with
removable jaws), and bored on each set-up to the disc outside diameter.
Avoid excessive chucking force.
2. True up the disc by means of an indicator, ensuring that the disc outside
diameter and seat face are true with each other within 0.002" full
indicator reading.
3. Machine light cuts across the seat at 90° to the axis until the damaged
areas are removed, facing to the smoothest possible finish. Rigidity of
the cutting tool is critical.
4. Relap flat across the full width of the raised seating surface.
5. Discard and replace the disc when the thickness is less than the value
in Appendix E.
6. See Appendix E for Critical Dimensions.
Lapping Compounds
The three grades of Farris Lapping Compounds are prepared especially for
the requirements of pressure relief valves. These are the only compounds
recommended for achieving extreme valve tightness, These compounds
are available in 2 ounce tubes. Use sparingly.
Lapping Procedures (Manual)
1. Use a cast iron lapping block or Pyrex lapping glass which is known to
have a perfectly flat face.
2. Select the appropriate lapping compound. When lapping the disc,
operate with a light figure eight motion over entire block surface. In this
way complete contact will be made (Figure 8.1).
Farris Lapping Compounds
Part No. Grade Finish Size
18632X1 (055) 3F Roughing 1/2 oz. tube
18633X1 (075) 38-500 Medium 1/2 oz. tube
18634X1 (105) 38-1200 Final 1/2 oz. tube
Figure 8.1
Lapping Plate Part
SAFETY
INSTRUCTIONS
Maintenance and repair
should only be performed
by properly trained and
authorized individuals.
PR
V
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