Figure 5-21.—Ferrules installed on tube, preset and removedfor inspection.b. For recessed-type ferrules, the leadingedge must be snug against the tube OD. Determinethis visually and by attempting to rock the ferruleon the tube.3. Ensure that the nut end of the ferrule (bothtypes) is collapsed around the tube to providesupport against bending loads and vibration.4. The ferrule (both types) must have little orno play along the direction of the tube run. Checkthis by trying to move the ferrule back and forthby hand. The ferrule will often be free to rotateon the tubing; this does not affect its function.5. For flush-type ferrules, check that the gapbetween the raised metal ridge and the cutting endof the ferrule stays the same while the ferrule isrotated. (Omit this check for recessed-type ferrulesor if the flush-type ferrule will not rotate on thetube).6. Check that the middle portion of the ferrule(both types) is bowed or sprung into an arc. Theleading edge of the ferrule may appear flattenedinto a cone shape; this is acceptable as long asthere is a bowed section near the middle of theferrule. If the whole leading section of the ferruleis flattened into a cone with no bowed section,the ferrule (and possibly the fitting body, if used)has been damaged by overtightening and will notseal reliably.Final AssemblyWhen you make a final assembly in thesystem, use the following installation procedure:1. Lubricate all threads with a liquid that iscompatible with the fluid to be used in the system.2. Place the tube assembly in position andcheck for alignment.3. Tighten the nut by hand until you feel anincrease in resistance to turning. This indicatesthat the sleeve or ferrule pilot has contacted thefitting.4. If possible, use a torque wrench to tightenflareless tubing nuts. Torque values for specificinstallations are usually listed in the applicabletechnical publications. If it is not possible to usea torque wrench, use the following procedures fortightening the nuts:After the nut is handtight, turn the nut 1/6turn (one flat on a hex nut) with a wrench. Usea wrench on the connector to prevent it fromturning while tightening the nut. After you installthe tube assembly, have the system pressure tested.Should a connection leak, you may tighten thenut an additional 1/6 turn (making a total of 1/3turn). If, after tightening the nut a total of 1/3turn, leakage still exists, remove the assembly andinspect the components of the assembly for scores,cracks, presence of foreign material, or damagefrom overtightening.NOTE: Overtightening a flareless-tube nutdrives the cutting edge of the sleeve or ferruledeeply into the tube, causing the tube to beweakened to the point where normal vibrationcould cause the tube to shear. After you completethe inspection (if you do not find any dis-crepancies), reassemble the connection and repeatthe pressure test procedures.CAUTION: Do not in any case tighten thenut beyond 1/3 turn (two flats on the hex nut);this is the maximum the fitting may be tightenedwithout the possibility of permanently damagingthe sleeve or the tube.CONNECTORS FORFLEXIBLE HOSEAs stated previously, the fabrication of flexiblehose assemblies is covered in applicable trainingmanuals, technical publications, and NAVAIR01-1A-20. There are various types of end fittingsfor both the piping connection side and the hose5-17
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