Instrumentation circuits

Arcing contacts in Division 2 areas must be installed in explosion-proof enclosures, be immersed in oil, be hermetically sealed, or be non-incendive. High-temperature devices must be installed in explosion-proof enclosures. Fuses must be enclosed in explosion-proof enclosures unless the fuses are preceded by an explosion-proof, hermetically sealed, or oil-immersed switch and the fuses are used for overcurrent protection of instrument circuits not subject to overloading in normal use. 

Ground fault interrupters should be included in all circuits used to power laboratory instrumentation. Circuit breakers should be near the areas they serve. Emergency lighting must be provided in each room, hallway and staircase. It is common practice to utilize battery powered lights for this purpose. House power is used to keep the batteries charged. 

Figure 1 shows the basic power and instrumentation circuit for a typical power supply based on the M-G (motor-generator) set. 

Understanding electrochemical instrumentation requires a basic knowledge of electricity and basic electronics. Coverage of these fundamentals is impossible in a text of this size. The student is advised to review the concepts of electricity learned in general physics, and to understand the definitions of current, voltage, resistance, and similar basic terms. The texts by Kissinger and Heineman, Malmstadt et al., or Diefenderfer and Holton, listed in the bibliography, are excellent sources of information on electronics used in instrumentation. The electrochemical cell is one circuit element with specific electrical properties in the complete instrumentation circuit. 

Piping and conduits. Process piping and duct work are installed in tunnels under the basement floor. This is necessary not only to properly shield them but also to keep them from occupying basement space. The bulk of the electrical conduits, excluding reactor control and instrument circuits, are... 

NUREG-0933, A prioritization of Generic Issues, July 1995, Generic Issue 142 Leakage through electrical isolators in instrumentation circuits. 

The term intrinsically safe applies to the apparatus and to the circuit in which is connected. It is normally associated with instrumentation circuits and some portable apparatus. This type of equipment may arc or spark... 

Check action of iiisirumenis, continuity of thermocouple connections and instrument circuits. Check control valves are correct for direction of flow and action on air failure H V H CHV... 

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