Broken wire fault

Here s a simple example of the covert failure problem. The output stage of the PLC operates a fail-safe solenoid or motor trip relay. It may have to stay energized for weeks but we won t know if it is shorted until it has to trip the function. This is an unrevealed fail to danger condition or covert fault . The broken wire fault is an overt fault or revealed fault, which will fail to a safe (off) state but creates a nuisance trip . 

Electromagnetic NDT instruments allow to increase the test records reliability. They are most efficient for detection of the rope durability loss as a result of loss of metallic cross-sectional area (LMA) localized faults (LF) like broken wires, localized corrosion etc. 

Fault A condition that causes a device, a component, or an element to fail to perform in a required manner. Examples include a short-circuit, broken wire, or intermittent connection. 

One purpose of grounding the neutral in a three-wire system is to activate overcurrent protection devices before damage is done when a fault occurs. Should one of the two wires that normally carries current be broken or accidentally grounded, current will flow through the neutral, through the installed ground, and back to the power source. This short circuit will open the protection devices and de-energize the affected portion of the system. 

In contrast to other heaters, there is a single coil inside the tube, and the positive and negative wires are located on opposite sides of the heater. This design largely eliminates the possibility of insulation breakdown. The cold ends of the heater, some 50 mm in length, are not heated and should be situated outside the manifold. One operational fault that occurs is that these ends get broken when care is not exercised in servicing. The thermal density of a tubular heater is about 15 W/cm. ... 

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