threaded ports in pumps, valves, and othercomponents. Several of these thread combinationsare shown in figure 5-16.Tubing used with flare connectors must beflared prior to assembly. The nut fits over thesleeve and when tightened, it draws the sleeve andtubing flare tightly against the male fitting to forma seal.The male fitting has a cone-shaped surfacewith the same angle as the inside of the flare. Thesleeve supports the tube so vibration does notconcentrate at the edge of the flare, and distributesthe shearing action over a wider area for addedstrength. Tube flaring is covered in Tools andTheir Uses, NAVEDTRA 10085 (series), andother applicable training manuals.Correct and incorrect methods of installingflared-tube connectors are illustrated in figure5-17. Tubing nuts should be tightened with atorque wrench to the value specified in applicabletechnical publications.If an aluminum alloy flared connector leaksafter being tightened to the required torque, itmust not be tightened further. Overtightening mayseverely damage or completely cut off the tubingflare or may result in damage to the sleeve or nut.The leaking connection must be disassembled andthe fault corrected.If a steel tube connection leaks, it may betightened 1/6 turn beyond the specified torque inan attempt to stop the leakage; then if it still leaks,it must be disassembled and repaired.Undertightening of connections may beserious, as this can allow the tubing to leak at theconnector bemuse of insufficient grip on the flareby the sleeve. The use of a torque wrench willprevent undertightening.CAUTIONA nut should never be tightened whenthere is pressure in the line, as this will tendto damage the connection without addingany appreciable torque to the connection.Figure 5-17.—Correct and incorrect methods of installing flared fittings.5-14
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