NZ/NZ-M and NZOS/NZOS-M Series
7
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Overpressure Protection
Overpressuring any portion of a regulator or associated equipment may cause personal injury, leakage or property damage
due to bursting of pressure-containing parts or explosion of accumulated gas. Provide appropriate pressure relieving or
pressure limiting devices to ensure that the limits in the Specifications section are not exceeded. Regulator operation within
ratings does not prevent the possibility of damage from external sources or from debris in the pipeline. Common methods of
external overpressure protection include relief valves, monitoring regulators, shutoff devices and series regulation.
Slam-Shut Device
Principle of Operation
The slam-shut device on Type NZOS/NZOS-M (Figure 2) can provide either overpressure (OPSO) or overpressure and
underpressure (OPSO/UPSO) protection by completely shutting off the flow of gas to the downstream system. Pressure from
the system is sensed through control line into the manometric sensing device (BMS). The device will transmit the pressure
fluctuations to the mechanism box (BM). If these fluctuations reach the set pressure of the sensing device, it will activate the
tripping mechanism in the BM and cause the valve to slam shut. After Type NZOS/NZOS-M has closed, it must be manually
reset before it can be put back in service. To reset the power stage, use the handle hanging outside the BM and rotate it
clockwise slowly.
4.
Installation
WARNING
Personal injury or equipment damage, due to bursting of pressure-containing parts may result if this regulator is
overpressured or is installed where service conditions could exceed the limits given in the Specification section and
on the appropriate nameplate or where conditions exceed any rating of the adjacent piping or piping connections.
To avoid such injury or damage, provide pressure-relieving or pressure-limiting devices to prevent service conditions
from exceeding those limits. Also, be sure the installation is in compliance with all applicable codes and regulations.
Additionally, physical damage to the regulator could break the pilot off the main valve, causing personal injury and
property damage due to bursting of pressure-containing parts. To avoid such injury and damage, install the regulator
in a safe location.
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INLET PRESSURE
OUTLET PRESSURE
LOADING PRESSURE
PILOT SUPPLY PRESSURE
ATMOSPHERIC PRESSURE
INTERMEDIATE PRESSURE
INLET PRESSURE
OUTLET PRESSURE
LOADING PRESSURE
PILOT SUPPLY PRESSURE
ATMOSPHERIC PRESSURE
INTERMEDIATE PRESSURE
MONITOR REGULATOR
WORKER
PILOT
Figure 5.
Type NZ Working Monitor System Operational Schematic
MONITOR
PILOT
WORKING REGULATOR
MONITOR
PILOT
Figure 6.
Type NZOS Working Monitor System Operational Schematic
WORKER
PILOT
WORKING REGULATOR
MONITOR REGULATOR