Flowserve NRG16-12 - Manual (Page 5)

5
Explanatory Notes
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Description
The level electrode NRG ...-2 detects the max. liquid level (high level alarm) in a steam boiler.
The operation of the electrode is based on the conductivity measuring principle using the electrical
conductivity of water for signaling one liquid level:
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High level alarm
The NRG ...-2 is designed for use in conjunction with level switch NRS -8 as a self-monitoring low
level limiter with periodic self-checking (SMART) feature.
Application in steam and pressurised hot-water plants in accordance with TRD 604, sheet  and
sheet 2 (24 h/72 h operation) as well as EN 2952 and EN 2953.
The electrical equipment meets the requirements of the Regulations on Protection Circuits
DIN VDE 06.
Function
The water level limiter comprises a level electrode type NRG ...-2 and a level switch type NRS -8.
The level electrode NRG ...-2 consists of a pressure-tight measuring electrode. The electrode is
insulated with a plastic sleeve.
The high level limiter is based on the conductive measuring principle using the electrical conductivity of
water for signaling water level. During normal, trouble-free operation the level electrode tip is not
immersed in boiler water and no high level alarm is given. A high level alarm will only be raised if the
electrode tip is submerged for more than 3 seconds. A high level alarm will also be activated if the
insulating seals placed between the electrodes and the body are no longer pressure tight, allowing
water to penetrate into the body. However in this instance the alarm is caused by a malfunction of the
electrode, and confirmation should always be done by checking the water level in the gauge glass.
The equipment combination NRG ...-2 and NRS -8 provides fail safe protection against a first fault in
accordance with TRD 604.
Scope of supply
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NRG 19-12
 Level electrode NRG 9-2, PN 60
 Joint ring 27 x 32, form D, DIN 7603, .430, bright-annealed
 Disk with set screw (measuring surface extension) – optional
 Retaining ring – optional
 Installation manual
System components
NRS 1-8
Level switch NRS 1-8. Two channel level limiter (redundancy) with periodic self-checking routine to
DIN VDE 06.