Safety Instructions For Raychem Ngc-40-Slim; Safety Function Of Temperature Limiter In Nvent Raychem Ngc-40-Slim; Area Of Use; Temperature Limiter (Schematic) - Raychem NGC-40-SLIM Manual

Temperature
Input 1
Temperature
Input 2
Limiter
Inputs
Temperature
Input 3
Limiter
Setpoint

3 SAFETY INSTRUCTIONS FOR RAYCHEM NGC-40-SLIM

3�1 Area of use
Safety temperature limiters are required in all areas where thermal processes need
to be prevented from overheating, and where the system must be set to a safe
operating condition in the event of a fault.
Typical examples of such installations could be surface heating installations in
Hazardous area Zone 1
3�2 Safety function of temperature limiter in RAYCHEM NGC-40-SLIM
The safety function will invoke, when the permissible temperature limit is reached
or in case a fault occurs (such as probe break, probe short-circuit, component
failure, or supply failure) even when the process conditions are within the
permissible temperature range. In all these cases the equipment is immediately
switched off. If the fault is no longer present, than the safety temperature function
must be manually reset before the unit goes back to normal operation. RAYCHEM
NGC-40-SLIM units can be reset by means of a Trip Reset push button, an external
hardwired signal or via dedicated software. The output of the unit will only be
enabled when all conditions are safe; meaning that the temperature measured
by the limiter RTD has dropped below the limiter set point and when there are no
other faults being detected. In other words, the unit will only reset after the normal
operating conditions have returned.
3�3 Temperature limiter (schematic)
Functional Safety Limiter block diagram
Temp 1
Comparison
Temp 2
Comparison
Temp 3
Comparison
Limiter main support circuitry including processor
Figure 11: Safety Temperature Limiter block diagram
Limiter
Limiter
Relay
Latching
O utput
Limiter
LEDs
Limiter
O utput
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