Figure 10-9.--Relief valve and rupture disc.
It is easy to detect a blown disc if you are around to
5. Disconnect the flexible tubing from the exhaust
hear it when it ruptures. If you are not there to hear it,
side of the component to be removed, and then
you may still notice it on your preoperational check.
remove the component (relief valve or rupture
Frost may form at the ruptured disc site, or you may see
disc). Tag the flexible line for easy reinstallation
visible vapor. If, however, you have observed neither of
the signs noted above, the condition will become
6. Clean old anti-seize tape (MIL-T-27730) from
apparent when you try to pressurize the LOX cart. You
all components to be reused.
will be unable to bring the cart to operating pressure
7. Install fresh anti-seize tape on the replacement
because of constant venting out of the ruptured disc or
parts. Start the tape at the third thread from the
the faulty relief valve.
Replacing a Blown Rupture Disc.--Use the
following steps for replacing a blown rupture disc:
8. Visually inspect all parts for dents, corrosion,
NOTE: Before beginning the procedure, make
and damaged threads, and inspect the valve
sure you have a replacement on hand.
packing gland and seat for damage. If found to
1. Ensure the storage and transfer tanks are empty
be unusable, replace with new parts.
and are at ambient temperature.
9. Replace the rupture disc, and install new valve
2. Connect a source of dry nitrogen gas to the
packing rings, where appropriate.
storage tank fill coupling (C-1).
Replacing a Defective Relief Valve.--Defective
3. Open both the fill-drain valve (LV-1) and the
relief valves cannot be adjusted or repaired; they are
storage tank vent valve (GV-6).
always replaced. Basically, you test a relief valve by
4. Sweep-purge the tank and piping by blowing
raising the operating pressure high enough to see if the
valve will open to bleed off excess pressure. When