Long unsupported loop Kink Sharp bend Crushed section Rub point Loose clamp Loose clamp Heat-sensing element Heat-sensing element Bracket Clamp hinge Grommet Clamp screw Figure 9-15.  Connector joint fitting attached to the structure. Figure 9-17.  Inspection of fire detector loop clamp. Figure 9-14.  Sensing element defects.  Figure 9-16.  Rubbing interference. 6.  Nuts at the end of the sensing elements  [Figure 9-15] should be inspected for tightness and the presence of  a safety wire. Loose nuts should be retorqued to the  value specified by the manufacturer’s instructions.  Some types of sensing element connection joints  require the use of copper crush gaskets, which should  be replaced any time a connection is separated. 7.  If shielded flexible leads are used, they should be  inspected for fraying of the outer braid. The braided  sheath is composed of many fine metal strands woven  into a protective covering surrounding the inner  insulated wire. Continuous bending of the cable or  rough treatment can break these fine wires, especially  those near the connectors. 8.  Sensing element routing and clamping should be  inspected carefully.  [Figure 9-14]  Long, unsupported  sections may permit excessive vibration that can cause  breakage. The distance between clamps on straight  runs, usually about 8–10 inches, is specified by the  manufacturer. At end connectors, the first support  clamp is usually located about four to six inches from  the end connector fittings. In most cases, a straight run  of one inch is maintained from all connectors before a  1.  Intermittent alarms are most often caused by an  intermittent short in the detector system wiring. Such  shorts may be caused by a loose wire that occasionally  touches a nearby terminal, a frayed wire brushing  against a structure, or a sensing element rubbing  against a structural member long enough to wear  through the insulation. Intermittent faults often can  be located by moving wires to re-create the short. 10. Grommets should be installed on the sensing element  so that both ends are centered on its clamp. The split  end of the grommet should face the outside of the  nearest bend. Clamps and grommets should fit the  element snugly.  [Figure 9-17] 9.  Interference between a cowl brace and a sensing  element can cause rubbing.  [Figure 9-16]  This  interference may cause wear and short the sensing  element. bend is started, and an optimum bend radius of three  inches is normally applied. The following troubleshooting procedures represent the  most common difficulties encountered in engine fire  detection systems: Fire Detection System Troubleshooting 9-12