Table 2-4. Support Clamp Spacing

TM 1-1500-204-23-3 (1) Metallines. Metal lines usually are made of stainless steel or an aluminum alloy. Check for leaks, loose anchorages, scratches, kinks, or other damage when inspecting. (2) Flexible hose. Flexible hose is made of synthetic rubber or Teflon. Special heat-resistant hose is used where the flexible lines will be subjected to intense heat. Fire-resistant hose is used for all fuel lines in the engine compartment. Check for leakage, looseness, cracks, or other damage when inspecting. (3) Removal and installation. Refer to TM 1-1500-204-23-2 for detailed information on fabrication, removal, and installation of fuel lines. General procedures are described in the following paragraphs. (a) Compatibility of fittings. All fittings are to be compatible with their mating parts. Although various types of fittings appear to be interchangeable, in many cases they have different thread pitch or minor design differences which prevent proper mating and may cause the joint to leak or fail. (b) Routing. Make sure that the line does not chafe against control cables, airframe structure, etc., or come in contact with electrical wiring or conduit. Where physical separation of the fuel lines from electrical wiring or conduit is impracticable, locate the fuel line below the wiring and clamp it securely to the airframe structure. In no case may wiring be supported by the fuel line. (c) Alignment. Locate bends accurately so that the tubing is aligned with all support clamps and end fittings and is not drawn, pulled, or otherwise forced into place by them. Never install a straight length of tubing between two rigidly mounted fittings. Always incorporate at least one bend between such fittings to absorb strain caused by vibration and temperature changes. (d) Bonding. Bond metallic fuel lines at each point where they are clamped to the structure. Integrally bonded and cushioned line support clamps are preferred to other clamping and bonding methods. (e) Support of line units. To prevent possible failure, all fittings heavy enough to cause the line to sag should be supported by means other than the tubing. (f) Support clamps. Rubber cushioned clamps should be installed in a manner to ensure ¼ inch minimum clearance between aircraft structure and fuel lines. They should be Installed so that the weight of the line tends to tighten attaching hardware. Support clamps should be spaced as shown in table 2-4 or, if near a bend, as close as possible to reduce overhang as shown in figure 2-3. Table 2-4. Support Clamp Spacing Approximate Tube distance between outer diameter supports (Inches) (inches) 1/8-3/16 9 1/4-5/16 12 3/8-1/2 16 5/8-3/4 22 1-1-1/4 30 1-1/2-2 40 Figure 2-3. Clamp Location for Tube Bends 2-7