Emerson NZ Series Instruction Manual page 6

NZ/NZ-M and NZOS/NZOS-M Series
Working Monitoring Systems
In a working monitoring system, the upstream regulator requires two pilots and it is always the monitoring regulator.
The additional pilot permits the monitoring regulator to act as a series regulator to control an intermediate pressure
during normal operation. In this way, both units are always operating and can be easily checked for proper operation.
In normal operation, the working regulator controls the outlet pressure of the system. The monitoring regulator's
working pilot controls the intermediate pressure and the monitoring pilot senses the system's outlet pressure. If the
working regulator fails, the monitoring pilot will sense the increase in outlet pressure and take control.
Figure 1. Type NZ Operational Schematic
TYPE NZ MAIN VALVE
INLET PRESSURE
OUTLET PRESSURE PILOT SUPPLY PRESSURE
LOADING PRESSURE ATMOSPHERIC PRESSURE
Figure 3. Type NZ/NZ-M Wide-Open Monitoring System with JPLC or JPHC Pilot Operational Schematic
INLET PRESSURE
OUTLET PRESSURE
TYPE JP PILOT:
LOADING PRESSURE L – LOADING
A – BALANCER
PILOT SUPPLY PRESSURE
B – SENSING
ATMOSPHERIC PRESSURE S – SUPPLY
Figure 4. Type NZ/NZ-M Wide-Open Monitoring System with JPLO or JPHO Pilot Operational Schematic
INLET PRESSURE
OUTLET PRESSURE
LOADING PRESSURE TYPE JP PILOT:
L – LOADING
PILOT SUPPLY PRESSURE
B – SENSING
ATMOSPHERIC PRESSURE S – SUPPLY
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TYPE JP PILOT
TYPE JP PILOT:
L – LOADING
B – SENSING
S – SUPPLY
TYPE JPLC/JPHC PILOT
TYPE JPLO/JPHO PILOT
TYPE NZ MONITOR
Figure 2. Type NZOS Operational Schematic
INLET PRESSURE
OUTLET PRESSURE
LOADING PRESSURE
TYPE NZ MONITOR TYPE NZ WORKING
TYPE JPLO/JPHO PILOT
TYPE NZ WORKING
TYPE JP PILOT:
L – LOADING
PILOT SUPPLY PRESSURE
B – SENSING
ATMOSPHERIC PRESSURE S – SUPPLY
TYPE JPLO/JPHO PILOT