XIX. Setting and Testing (Cont.)
(iv) Snoop joint between the modulator and
pilot and the weep hole that is located
behind Warning tag. If bubbles are
present, repair as necessary.
7. Setting of 49MV22 and 49MV72.
a. If Adjuster Assembly has not been previously
set, turn Adjuster into Pilot Base until it stops.
Turn out 2 turns.
b. For the 49MV22, pilot will begin to vent at
98.1% of the Main Valve set pressure. For the
49MV72, pilot will begin to vent at 97.3% of
the main valve set point.
c. To determine what pressure venting should
occur, multiply the set pressure by 0.981 for
49MV22 and 0.973 for the 49MV72.
d. At the set point, the dome pressure should be
70% of the set pressure.
e. Example: 49MV22 valve set at 751 psig (51.8
barg). Venting should begin when pressure
is 730 psig (50.3 barg) (751 x 0.981). Dome
pressure will be 527 psig (36.3 barg) at the set
pressure of 751 psig (51.8 barg) (751x0.70).
8. Adjusting blowdown on 49MV22 and 49MV72.
a. Raise inlet pressure until the inlet pressure
is at 10% or 3 psig (0.21 barg), whichever is
greater, above set pressure.
b. Slowly lower the inlet pressure until the
dome pressure starts to rise. Hold inlet
pressure steady until the dome pressure
stops rising.
c. Lower the inlet pressure in 3 to 5 psig (
0.21 to 0.35 barg) increments. Hold inlet
pressure until dome pressure stops rising.
d. Repeat step 8.c until the dome pressure is
70% of the valve set pressure.
e. Note the inlet pressure when the dome
pressure is at 70% of set pressure. This will
be the blowdown.
f. If blowdown is too long, turn Adjuster one
flat counterclockwise. If blowdown is too
short, turn Adjuster one flat clockwise (only
adjust when there is zero pressure on the
pilot).
g. Repeat steps 8.a to 8.f until blowdown
is correct.
h. After adjustments have been completed,
tighten Compression Screw Lock Nut on
Compression Screw and Adjuster Cap to
secure settings.
i. Check for leakage at 96% of set pressure.
9. Final assembly of 49PV:
a. Thread Cap (Compression Screw) onto
Bonnet and tighten wrench tight.
b. For Lifting Lever Option,
(i) Install Lifting Lever Assembly by turning
Cam Bushing clockwise.
(ii) Make certain that the Cam Shaft sits just
under Release Nut.
c. Pilot is now ready for assembly to the main
base.
10. Final assembly of 49MV:
a. Thread Cap (Compression Screw) onto
Bonnet and tighten wrench tight.
b. For Lifting Lever Option,
(i) Install Lifting Lever Assembly by turning
Cam Bushing clockwise.
(ii) Make certain that the Cam Shaft sits just
under Release Nut.
(iii) Pilot is now ready for assembly to the
main base.
Once the pilot valve set pressure and blowdown
are calibrated on the pilot valve test stand, and the
pilot valve is installed on the main valve, only the set
pressure may be tested and adjusted if necessary
on a shop test stand.
Note:
Blowdown can be set and checked on the
main valve only if the shop test stand can
achieve 10% over pressure.
Consolidated 4900 MPV Series POSRV Manual
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