caused personnel injury, damage to equip-ment, and unnecessary interruption ofpropulsion power.1. Cut the tubing square and lightly deburrthe inside and outside corners. For corrosionresisting steel (CRES) tubing, use a hacksaw ratherthan a tubing cutter to avoid work hardening thetube end. For CRES, and if necessary for othermaterials, dress the tube end smooth and squarewith a file. Tube ends with irregular cutting markswill not produce satisfactory seating surfaceimpressions.2. Test the hardness of the ferrule by makinga light scratch on the tubing at least 1/2 inch backfrom the tube end, using a sharp corner on theferrule. If the ferrule will not scratch the tube,no bite will be obtained. This test maybe omittedfor flush-type ferrules where the bite will bevisible. Moderate hand pressure is sufficient forproducing the scratch.3. Lubricate the nut threads, the ferruleleading and trailing edges, and the preset toolthreads with a thread lubricant compatible withthe system. Slide the nut onto the tubing so thethreads face the tube end. Note whether theferrule is a flush type or recessed type (fig. 5-19),and slide the ferrule onto the tube so the cuttingedge is toward the tube end (large end toward thenut).4. Bottom the end of the tubing in thepresetting tool. Slide the ferrule up into thepresetting tool, and confirm that the nut can bemoved down the tube sufficiently to expose atleast 1/8 inch of tubing past the ferrule after thepresetting operation (fig. 5-20) to allow forinspection of the ferrule.5. While keeping the tube bottomed in thepresetting tool, tighten the nut onto the fittingbody until the ferrule just grips the tube byfriction. This ring grip point may be identified bylightly turning the tube or the presetting tool andslowly tightening the nut until the tube cannotbe turned in the presetting tool by hand.Mark the nut and the presetting tool at thisposition.6. Tighten the nut according to the numberof turns given in table 5-3, depending on tubesize.5-16Figure 5-20.—Tube and ferrule assembled for preset-ting, showing nut position required for inspectingferrule.InspectionDisassemble and inspect the fitting as follows(mandatory):1. Ensure that the end of the tubing has animpression of the presetting tool seat surface(circular appearing ring) for 360 degrees. A partialcircle, a visibly off-center circle, or a circle brokenby the roughness of the tube end is unsatisfactory.2. Check for proper bite:a. For flush-type ferrules, a raised ridge(fig. 5-21) of tube metal must be visible completelyaround the tube at the leading edge of the ferrule.The best practice is to obtain a ridge about 50percent of the ferrule edge thickness.Table 5-3.—Number of Turns
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