(j)
Remove the valve test fixture from the airplane.
(k)
Disconnect the air source from the pressure regulator.
S 725-008
(3) Do the test for the other safety relief valve.
TASK 21-32-21-725-004
3. Test Safety Relief Valve Using Boeing Test Equipment (Fig. 501)____________________________________________________
A. Equipment
(1)
A21010-70 Vacuum Tank - Safety Relief Valve (recommended) A21010-63 Vacuum Tank - Safety Relief Valve (alternative)
(2)
Air compressor or air source - capable of 60-80 psi at 22 scfm, commercially available.
B. Access
(1) Location Zone
220 Aft Cargo Compartment Equipment Bay
C. Procedure
S 845-005
(1) Prepare for the test:
(a)
Make sure all the valves on the test equipment are closed.
(b)
Connect the air pressure source to the quick-disconnect air connection on the vacuum tank assembly.
(c)
Make sure the vacuum regulator valve on the vacuum tank assembly is turned fully clockwise.
(d)
Adjust the air control valve until the indication on the pressure gage is 70 (+10/-10) psi.
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(e) Adjust the vacuum regulator valve until the differential pressure is approximately 2.0 psi.
NOTE: Turn the vacuum regulator valve counter-clockwise to
____ increase the vacuum (differential pressure). The arrow on the vacuum regulator valve indicates an increase of pressure not vacuum.
CAUTION: DO NOT LET THE VACUUM HEAD ASSEMBLY FALL DURING THE TEST.
_______ IF THERE IS NO VACUUM, THE VACUUM HEAD WILL NOT STAY ON THE AIRPLANE. IF THE VACUUM HEAD FALLS, THE VACUUM HEAD ASSEMBLY WILL BE DAMAGED.
(f) Put the vacuum head assembly on the safety relief valve on the airplane and open the vacuum head assembly valve.
S 725-006
(2) Do the test:
(a)
Adjust the vacuum regulator valve so the indication on the vacuum rate gage does not exceed 2.4 psi/minute.
(b)
When the differential pressure gage shows 7.6 psid, adjust the vacuum regulator valve to increase the differential pressure in
0.05 psi increments.
(c)
Stop the increase of vacuum for 10 seconds between each increase of 0.05 psid.
(d)
Continue the intermittent vacuum increases of 0.05 psid until the safety relief valve opens.
(e)
Monitor the indication on the differential pressure gage when the valve opens.
NOTE: The valve must open at a differential pressure of 8.25
____ to 8.74 psi (16.8 to 17.8 inches Hg).
The indication that the relief valve opens is seen on the differential pressure gage when the pressure starts to decrease, or on the vacuum rate gage when the vacuum rate goes to zero.
(f) Make sure the tubing connections are tight if the valve opens at a value that is too large.
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(g) Do these steps to make sure that the valve seat on the safety relief valve has fully closed: 1) Adjust the vacuum regulator valve so the indication on the
vacuum rate gage does not exceed 2.4 psi/minute.
2) Make sure that you are able to increase the vacuum until the differential pressure gage shows 7.0 psid. a) This shows that the valve seat on the safety relief
valve has closed.
(h)
Adjust the vacuum regulator valve until the differential pressure is approximately 2.0 psi at a rate not more than 4.0 psi/min.
(i)
Close the vacuum head assembly valve and remove the vacuum head assembly.
(j)
Adjust the vacuum regulator valve fully clockwise and reduce the differential pressure to zero psi.
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