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Companion 1000/T Liquid Oxygen System Technical Manual
5.1.2
5.1.3
5.1.4
B-701964-00 Rev. C
Compression Fitting Remake
When disassembling a compression fitting, mark the tube nut and the fitting body
before disassembly. To remake the connection, tighten the tube nut until the marks
realign. A slight torque increase indicates the ferrule is being re-sprung into sealing
position. After several remakes, it may become necessary to advance the tube nut
slightly past the original position. This advance need only be 15° to 20° (
hex flat). In situations where the existing tube with seated ferrule is to be used with a
replacement fitting body, tighten the tube nut until a slight torque increase indicates the
ferrule is being re-sprung into sealing position. Advance the nut an additional 15° to
20°.
Compression Fitting Troubleshooting
Most leaks in compression fittings are the result of improper connections. Typically the
tube is either not aligned squarely in the fitting body before connection or the tube is
not secured against the stop during connection. In addition, overtightening may also
result in a cracked fitting body that will leak.
To check for leaks, pressurize the system and use an oxygen-compatible leak detector
(such as SNOOP) on the fitting. If bubbles form at the back of the nut between the nut
and the tube, you probably did not get a seal between the ferrule and the tube;
misalignment may be the cause. However, check the tube itself; there may be a scratch
or seam running along the tube, allowing a leak to occur.
If the leak detector forms bubbles at the front of the nut, between it and the fitting body,
then the leak is probably between the ferrule and the fitting's tapered seat. Check this
area for imbedded dirt or cracks.
Tapered Pipe Thread Makeup
Some components used in the Companion 1000/T have NPT threads (Figure 5-3). NPT
threads create leak-tight connections provided a thread sealant (such as Teflon tape) is
used on the threads.
Figure 5-3: NPT Fittings (National Pipe Tapered)
Perform the following steps when making up a new NPT fitting:
1. Remove old thread sealant. Use a wire brush to remove sealant or dirt from male
and female threads of NPT fittings. Make sure contaminants do not drop into the
fittings during the cleaning process.
2. Apply thread sealant to the male threads. Apply two to three layers of Teflon tape
to the male threads starting two threads back from the end (Figure 5-4). Wrap the
Teflon tape clockwise (as viewed from thread end of fitting) to prevent unraveling
when installing the fitting.
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Service and Repair 5-3
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Troubleshooting
