(7)
Put liquid nitrogen (-320°F) into a small, insulated container.

 S 948-351
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747-400 MAINTENANCE MANUAL
 S 948-352
 WARNING: SLOWLY AND CAREFULLY SUBMERGE WARM ITEMS IN LIQUID NITROGEN TO
_______ PREVENT RAPID BOILING OFF AND SPLASHING. MISSUSE OF LIQUID NITROGEN CAN CAUSE INJURY TO PERSONS.
 (8)  
Remove the Cryofit coupling from the main storage container and put it into the small container of liquid nitrogen. Make sure the coupling is fully covered by theliquid nitrogen.

 S 948-353

 (9)  
Move the Cryofit coupling in the liquid nitrogen (-320°F) to the repair location.

 S 948-354

 (10)
 Put the tongs and the tube chiller into the small container of liquid nitrogen.

 S 438-355

 (11)
 Slip the test coupling (from the installation kit) over the tube ends to ensure that tubes are round and free of burrs. The test coupling should slide freely.

 S 438-356

 (12)
 Position the test coupling so that both tubes are visible in the coupling window. For 3PO2111 couplings, ensure that a gap of less than 0.120 inch exists between the tube ends. For 3PHS111 couplings, ensure that the gap is less than 0.300 inch.

 S 438-357

 (13)
 Remove the test coupling and place the marking gauge over one of the tube ends. Using the marking pen, color in the rectangular slot in the gauge to provide an installation mark on the tube. Follow the same procedure to mark the remaining tube end.

 S 438-358

 (14)
 Place an installation stop ("O" ring), or snap-on coupling in the middle of the mark on one of the tube ends. Check the location by positioning the test coupling so that it is butted against the stop. Both tube ends should be visible in the window and the test coupling should cover approximately half the installation mark on each tube. Adjust the tubes and installation stop as necessary. Remove the test coupling.

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A
747-400
MAINTENANCE MANUAL

 S 438-359
 (15)
 Ensure that the tube ends, within half the coupling length of the end, are free of scratches. If a fitting must be installed over a tube end containing a scratch, apply a thin layer (one to two drops) of Loctite 290 around the tube circumference in the area under the serrations. Be careful not to let the Loctite into the tube. No Loctite application is required for tube ends without scratches.

 S 038-360

 (16)
 For 3PO2111, remove a Cryofit coupling from the liquid nitrogen and immediately place it into a pre-chilled extended time tool. Close the tool and immediately return the coupling/tool to liquid nitrogen. This step is omitted for 3PHS111 couplings since they are pre-assembled in the tool and furnished in Lexan plastic packaging from the manufacturer.

 S 438-361

 (17)
 Place the cooled tube chiller over the tubes to be joined.  Remove the chiller after 20 to 30 seconds.

 NOTE:____This step may be omitted. However, placing the Cryofit coupling in contact with a tube which has not been pre-chilled with liquid nitrogen may initiate premature warming and shrinkage of the coupling.
 S 438-362
 (18) Install the coupling by following the steps below in rapid sequence:
 (a)  
Remove the tube chiller from the tubes.

 (b)  
Using the cooled tongs, remove the Cryofit installation package from the liquid nitrogen and grasp the package between thumb and forefinger.

 (c)  
Deflect the tube without the installation stop to allow the coupling to be slipped over the tube end.

 (d)  
Slip the coupling on to the tube, realign the tubes and slide the coupling against the installation stop.
　
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