GESTRA
GESTRA Steam Systems
NRG 16-12
NRG 17-12
NRG 19-12

Installation Instructions 818626-00
Level Electrode
NRG 16-12, NRG 17-12, NRG 19-12
Contents
Page
Important Notes
Usage for the intended purpose...............................................................................................................4
Safety note..............................................................................................................................................4
Danger....................................................................................................................................................4
ATEX (Atmosphère Explosible)..................................................................................................................4
Explanatory Notes
Scope of supply................................................................................................................................... 4-5
Description..............................................................................................................................................5
Function..................................................................................................................................................5
System components................................................................................................................................5
Design.....................................................................................................................................................6
Technical Data
NRG 16-12, NRG 17-12, NRG 19-12........................................................................................................6
Corrosion resistance................................................................................................................................7
Sizing......................................................................................................................................................7
Name plate / marking..............................................................................................................................7
Dimensions..............................................................................................................................................8
Design
NRG 1...-12.............................................................................................................................................9
Key........................................................................................................................................................11
Functional Elements
NRG 1...-12...........................................................................................................................................10
Key........................................................................................................................................................11
Installation
NRG 1...-12, step 1................................................................................................................................12
NRG 1...-12, step 2................................................................................................................................12
Attention................................................................................................................................................12
Important notes.....................................................................................................................................13
Tools......................................................................................................................................................13
Examples of installation.........................................................................................................................14
Key........................................................................................................................................................15
Contents
– continued –
Page
Wiring
NRG 1...-12...........................................................................................................................................15
Wiring diagram......................................................................................................................................16
Voltage table..........................................................................................................................................17
Note......................................................................................................................................................17
Tools......................................................................................................................................................17
Commissioning
Check wiring.........................................................................................................................................17
Apply mains voltage..............................................................................................................................17
Operation
High-level alarm....................................................................................................................................18
Note......................................................................................................................................................18
Operational Malfunctions
Fault-finding list for troubleshooting.......................................................................................................18
Decommissioning
Danger..................................................................................................................................................19
Disposal................................................................................................................................................19
Important Notes
Usage for the intended purpose
Use level electrodes NRG 16-12, NRG 17-12 and NRG 19-12 only in conjunction with level switch NRS
1-8 for water-level limiting (high level alarm).
Safety note
The equipment must only be installed and commissioned by qualified and competent staff.
Retrofitting and maintenance work must only be performed by qualified staff – who through adequate
training – have achieved a recognised level of competence.
Danger
When loosening the electrode steam or hot water might escape.
This presents the danger of severe scalds to the whole body.
It is essential not to mount or dismantle the electrode unless the boiler pressure is
verified to be 0 bar. The electrode becomes hot during operation. Touching the hot
equipment presents the risk of severe burns to hands and arms. All installation and
maintenance work must only be performed when the equipment is cold.
ATEX (Atmosphère Explosible)
The equipment constitutes a simple item of electrical equipment as defined in DIN EN 50020 section
5.4. According to the European Directive ATEX 94/9/EC the equipment may only be used in potentially
explosive atmospheres if it is provided with approved Zener barriers.
Applicable in Ex zones 1, 2 (1999/92/EC). The equipment does not bear an Ex marking. The suitability
of the Zener barriers is certified in a separate document.
Explanatory Notes
Scope of supply
NRG 16-12
1 Level electrode NRG 16-12, PN 40
1 Joint ring 27 x 32, form D, DIN 7603, 1.4301, bright-annealed
1 Disk with set screw (measuring surface extension) – optional
1 Retaining ring – optional
1 Installation manual
NRG 17-12
1 Level electrode NRG 17-12, PN 63
1 Joint ring 27 x 32, form D, DIN 7603, 1.4301, bright-annealed
1 Disk with set screw (measuring surface extension) – optional
1 Retaining ring – optional
1 Installation manual
Explanatory Notes
Scope of supply
– continued –
– continued –
NRG 19-12
1 Level electrode NRG 19-12, PN 160
1 Joint ring 27 x 32, form D, DIN 7603, 1.4301, bright-annealed
1 Disk with set screw (measuring surface extension) – optional
1 Retaining ring – optional
1 Installation manual
Description
The level electrode NRG 1...-12 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:
■ High level alarm
The NRG 1...-12 is designed for use in conjunction with level switch NRS 1-8 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 1 and
sheet 2 (24 h/72 h operation) as well as EN 12952 and EN 12953.
The electrical equipment meets the requirements of the Regulations on Protection Circuits
DIN VDE 0116.
Function
The water level limiter comprises a level electrode type NRG 1...-12 and a level switch type NRS 1-8.
The level electrode NRG 1...-12 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 1...-12 and NRS 1-8 provides fail safe protection against a first fault in
accordance with TRD 604.
System components
NRS 1-8
Level switch NRS 1-8. Two channel level limiter (redundancy) with periodic self-checking routine to
DIN VDE 0116.
Explanatory Notes
– continued –
Design
NRS 1...-12
Screwed ¾" BSP, ISO 228-1, Fig. 3, Fig. 4, Fig. 5.
Technical Data
NRG 16-12, NRG 17-12, NRG 19-12
Type approval
TÜV· 01-02-0112
Service pressure
NRG 16-12: 32 bar at 238 °C
NRG 17-12: 60 bar at 275 °C
NRG 19-12: 100 bar at 311 °C
Connection
¾" BSP, ISO 228-1
Materials
Stem: 1.4571 X6CrNiMoTi17-12-2
Measuring electrode: 1.4401, X5CrNiMo17-12-2
Electrode insulation: PEEK
Terminal box: Polyamide (PA)
Lengths available
500 mm1000 mm
1500 mm
Cell constant C
0.13 cm-1 with measuring surface extension
0.3 cm-1 without measuring surface extension
Response sensitivity
10 µS/cm at 25 °C, cell constant 0.3 cm-1
0.5 µS/cm at 25 °C, cell constant 0.13 cm-1
Terminal box
Four-pin connector, cable gland M 16 (PG 9)
Protection
IP 65 to EN 60529
Max. admissible ambient temperature
70 °C
Weight
Approx. 1.1 kg
Technical Data
– continued –
Corrosion resistance
Provided that the equipment is used for its intended purpose, its safety is not impaired by
corrosion.
Sizing
The body must not be subjected to sharp increases in pressure. Welds and flanges of the electrode are
designed to withstand dynamic loading (bending and alternating stress). The dimensional allowances
for corrosion reflect the latest state of technology.
Name plate / marking
Equipment designation
Fig. 1
Fig. 2
Technical Data
– continued –
120
85
85
165
283
272
Dimensions
30
30
≤ 1500
8
≤ 1500
≤ 1500
30
23
Fig. 3
Fig. 4
Fig. 5
NRG 16-12 with
NRG 17-12 without
NRG 19-12 without
measuring surface extension
measuring surface extension
measuring surface extension
Design NRG 1...-12
S
A
B
C
D
Fig. 6
G
F
E
J
I
H
Fig. 7
∅ 33
Fig. 8
0.5
N8
N 10
¾" BSP, ISO 228-1
Fig. 9
Functional Elements NRG 1...-12
K
L
R
M
Q
N
O
P
Fig. 10
10
Key
A
Measuring electrode
B
Bore
C
Spring
D
Electrode tip
E
Disk (measuring surface extension)
F
Star-lock washer
G
Set screw
H
Joint ring 27 x 32, form D, DIN 7603, 1.4301, bright-annealed
I
Seating surface
J
Electrode thread
K
Screw M4
L
Lid
M
Upper part of terminal box
N
Connecting plate
O
Sealing element
P
Contact plate for level electrode
Q
Cable gland M 16 (PG 9)
R
Cable clamp
S
Thermal insulation, provided on site, d = 20 mm
(outside of thermal insulation of steam generating unit)
11
Installation
NRG 1...-12, step 1
1. Screw electrode tip D into measuring electrode A, Fig. 6
2. Carefully determine required measuring length, taking minimum length into account.
3. Mark length of electrode tip D.
4. Unscrew electrode tip D from measuring electrode A and cut tip.
5. Screw electrode tip D into measuring electrode A and tighten. Slide spring C along electrode tip
D, so that its bent end completely enters into small bore B.
6. If a measuring surface extension is required slip disk E onto electrode tip D ensuring that the
electrode tip protrudes 2 mm from the bottom of the disk. Fasten disk with set screw G.
Push star-lock washer F over electrode tip against disk.
NRG 1...-12, step 2
1. Check seating surfaces, Fig. 9
2. Place joint ring H onto seating surface I of electrode, Fig. 7
3. Apply a light smear of silicone grease (e. g. Molykote® 111) to electrode thread J.
4. Screw level electrode into threads of flange provided on vessel and tighten with a 36 mm ring
spanner. The torque required is 160 Nm when cold.
Attention
■ The seating surfaces and threads on the vessel and mounting flange must be accurately
machined, Fig. 9
■ Use GESTRA PN 160 hat flange when applying the equipment in a high-pressure steam
boiler.
■ Do not bend the electrode tip when cutting.
■ Use only the supplied ring joint 27 x 32, form D, DIN 7603, 1.4301, bright-annealed.
■ Do not lag the electrode body.
■ Do not insulate the threads with hemp or PTFE tape.
■ Do not apply conductive paste or grease to the electrode thread.
■ Provide a min. spacing of 14 mm between electrode and earth (flange, boiler wall),
Fig. 11, Fig. 12, Fig. 13, Fig. 14
■ Observe the minimum distances for the installation of the electrode, Fig 14
Molykote® 111 is a registered trademark of DOW Corning Corp., Midland Michigan, USA
12
Installation
– continued –
Important notes
■ For the approval of the boiler standpipe the relevant regulations must be observed.
■ For typical installation examples refer to page 14.
■ When mounting the electrode laterally make sure that the inclination angle does not
exceed 45° and that the length of the electrode rod is limited to 1000 mm. Fig. 12
■ If the electrode is installed outdoor, it must be provided with a weather-proof cover
supplied by GESTRA.
Tools
■ Open-end spanner A. F. 13
■ Open-end spanner A. F. 36
■ Scriber
■ Hacksaw
■ Flat file, cut 2
13
Examples of Installation
¾" BSP
45°
1
2
∅ 20
8
4
20
DN 50
3
≥1
m
ax
.
10
00
4
5
6
≤ 90°
20
9
0
∅ 20
Fig. 11
Fig. 12
¾" BSP
¾" BSP
DN 100
∅ 20
20
24.5 24.5
3
4
≤ 90°
≤ 3000
1
2
DN 20
4
Centre distance
¾" BSP
5
7
8
4
9
!
≤ 20
1
5
9
DN 20
∅ 20
Fig. 13
14
Fig. 14
DN 20
Key
1 Flange PN 40, PN 63, PN 160, DN 50, DIN 2501-1
Flange PN 40, PN 63, PN 160, DN 100, DIN 2501-1
2
For the approval of the boiler standpipe the relevant regulations must be considered.
3
Vent hole
4
High water HW
5
Electrode rod d = 8 mm
6
Protection tube DN 80
7
Protection tube DN 100
8
Electrode distance
9
Low water LW
0
Reducer DIN 2616-2, K-88.9 x 3.2 – 42.4 x 2.6 W
Provide bore as close as possible to the boiler wall!
≥ 14 mm
Wiring
NRG 1...-12
Note that screened four-core cable, e. g. I-Y(St)Y 2 x 2 x 0.8 or LIYCY 4 x 0.5 mm² is required for wiring
the electrode.
Max. length 100 m with conductivites from 10 µS/cm.
Max. length 30 m with conductivites from 0.5 µS/cm.
Max. length 15 m with conductivites from 0.5 µS/cm and application of the ancillary unit URN 1
(24 V DC).
1. Unscrew screw K, Fig. 10
2. Take the terminal box off the level electrode, leaving the sealing element O on the contact
plate P .
3. Remove lid L.
4. Press connecting plate N out of the upper part of the terminal box M.
The upper part of the terminal box can be turned in steps of 90°.
5. Detach cable gland Q and cable clamp R from the upper part of the terminal box M.
6. Run cable through cable gland Q and upper terminal box M and connect the terminals of the connecting plate N according to the wiring diagram.
7. Press connecting plate N into the upper part of the terminal box and align the cable.
8. Hold cable with cable clamp R and cable gland Q in position.
9. Mount lid L and insert screw K.
10. Put upper part of the terminal box onto the level electrode and fix it firmly with screw K.
15
Wiring
– continued –
Wiring diagram
NRS 1-8
U1-2
Fig. 15
NRS 1-8
U1-2
Fig. 16
This wiring diagram is only valid for France.
16
Wiring
– continued –
Voltage table
Use this voltage table as a reference when checking whether the level electrode is submerged or if
there is a malfunction. Please take the wiring diagram of the electrode NRS 1-8 into account.
Fig. 15, Fig. 16
U1-2
U1-2
10 µS/cm
0.5 µS/cm
2 Veff
C=0.3 cm-1
10 Veff
C = 0.13 cm-1
Note
■ The self-checking routine of the amplifier NRS 1-8 reduces U1-2 every 40 seconds to
0 volt!
Tools
■ Screwdriver for cross-recess head screws, size 1
■ Screwdriver for slotted screws, size 2.5, completely insulated according to DIN VDE 0680-1
■ Open-end spanner A. F. 18 (19)
Commissioning
Check wiring
Check whether the NRG 1…-12 and the associated controller NRS 1-8 are wired in accordance with
the wiring diagram. Fig. 15, Fig. 16
Apply mains voltage
Apply mains voltage to level switch NRS 1-8.
17
Operation
High-level alarm
Operation in combination with controller NRS 1-8 in steam and pressurised hot water plants to
TRD 401, TRD 602, TRD 604, EN 12952, EN 12953 or other national regulations.
Note
■ Should malfunctions occur during the commissioning procedure refer to chapter
“Operational Malfunctions” on page 18 in order to analyse and correct them.
Operational Malfunctions
Fault-finding list for troubleshooting
Level electrode exposed – high-level alarm
Fault:
Mains voltage is not applied to level switch.
Remedy: Apply mains voltage. Wire electrode according to wiring diagram.
Fault:
The electrode rods have earth contact.
Remedy: Check and change position of installation.
Fault:
The internal insulation of the electrode rod is damaged.
Remedy: Replace level electrode.
High level reached – no function
Fault:
The electrode housing does not have earth connection to the boiler.
Remedy: Clean seating surfaces and insert metal joint ring (of stainless steel 1.4301) 27 x 32,
form D, DIN 7603, bright-annealed.
Do not insulate level electrode with hemp of PTFE tape.
Fault:
The vent hole in the protection tube does not exist, is obstructed or flooded.
Remedy: Check protection tube and, if necessary, provide vent hole.
Fault:
The isolating valves of the external measuring pot (optional extra) are closed.
Remedy: Open isolating valves.
If faults occur that are not listed above or cannot be corrected, please contact our Technical
Service or authorized agency in your country.
18
Decommissioning
Danger
Risk of severe burns and scalds to the whole body!
Before removing the level electrode make sure that the vessel or measuring pot are
depressurised (0 bar) and cooled down to room temperature (20 °C).
Disposal
Remove the level electrode and separate the waste materials in accordance with the material
specification.
Electronic components (boards) must be disposed of separately.
For the disposal of the level electrode observe the pertinent legal regulations concerning waste
disposal.
19
GESTRA
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Tel.
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Fax
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818626-00/306cm · © 2003 GESTRA AG · Bremen · Printed in Germany
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