Flowserve NRS 1-51 User Manual
GESTRA
GESTRA Steam Systems
NRS 1-51
Installation Instructions 818955-01
Level Switch
NRS 1-51
EN
English
1
2
Contents
Page
Application
Usage for the intended purpose ..............................................................................................................4
Function .................................................................................................................................................4
Directives and Standards
Pressure Equipment Directive (PED) 97/23/EC ........................................................................................
Functional Safety acc. to IEC 61508 ........................................................................................................
VdTÜV Bulletin “Wasserstand 100” (= Water Level 100) ..........................................................................
LV (Low Voltage) Directive and EMC (Electromagnetic Compatibility) .......................................................5
ATEX (Atmosphère Explosible) .................................................................................................................5
Functional Safety acc. to IEC 61508
Safety characteristics of the subsystem NRG 1...-51 / NRS 1-51 .............................................................
Terms and abbreviations .........................................................................................................................6
Determination of the Safety Integrity Level (SIL) for safety-related systems .............................................7
Technical Data
NRS 1-51
Name plate / marking ...........................................................................................................................10
Dimensions and Functional Elements
NRS 1-51..............................................................................................................................................11
Important Notes
Safety note ...........................................................................................................................................12
Scope of supply ....................................................................................................................................12
Installation
............................................................................................................................................ 8, 9
5
5
5
6
Mounting level switch NRS 1-51 ........................................................................................................... 13
Contents – continued –
Page
Electrical Connection
Mains supply ........................................................................................................................................13
Connection of level electrode ................................................................................................................ 13
Connection of control circuit .................................................................................................................13
Connection of logic unit (standby input).................................................................................................13
Connection for signal output .................................................................................................................14
Tools .....................................................................................................................................................14
Wiring diagram for level switch NRS 1-51 .............................................................................................15
Schematic representations of arrangements .........................................................................................16
Explanatory notes to schematic respresentations .................................................................................. 16
Basic Settings
Factory setting ......................................................................................................................................16
Commissioning Procedure
Checking switchpoint and function .......................................................................................................17
Operation, Alarm and Test
Indicators and adjustors ........................................................................................................................18
Troubleshooting
Indication, diagnosis and remedy .................................................................................................... 18, 19
Further Notes
Action against high frequency interference ...........................................................................................20
Interlock and interlock deactivation .......................................................................................................20
Checking the switchpoints .................................................................................................................... 20
Decommissioning / replacing level switch .............................................................................................20
Disposal................................................................................................................................................20
Note on the Declaration of Conformity / Declaration by the Manufacturer .........................................20
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4
Application
Usage for the intended purpose
The level switch NRS 1-51 is used in conjunction with level electrodes NRG 1...-.. as high level alarm in
steam boilers and (pressurised) hot-water plants.
A high level alarm prevents the water level from exceeding the preset max. water level (HW) and for this
purpose switches off e. g. the feedwater supply.
Depending on the specified directives or standards, the level switch NRS 1-51 is intended to be used in
combination with the following level electrodes:
Level electrode NRG 1...-..
PED Pressure Equipment Directive
97/23/EC +
Functional Safety IEC 61508 SIL 3
VdTÜV Bulletin “Wasserstand 100”
(= Water Level 100)
Function
The level switch NRS 1-51 is designed for different electrical conductivities of the boiler water and for
connecting one level electrode.
See section Schematic representations of arrangements on page 16.
When the water level exceeds the MAX limit, the level electrode enters the liquid and an alarm is
triggered in the level switch. This switchpoint is determined by the length of the electrode rod
(level electrode NRG 1...-51, NRG 1...-12).
After the de-energizing delay has elapsed, both output contacts of the level switch will open the control
circuit, e. g. for the feedwater supply. If the deactivation of the feedwater supply is interlocked in the
external control circuit, the lockout can only de deactivated when the level electrode is exposed again.
An alarm will also be raised if a malfunction occurs in the level electrode and/or the electrical connection.
If the level electrode is installed in an isolatable level pot outside the boiler, make sure that the connecting
lines are rinsed regularly.
minutes.
(standby input, controlled by the logic unit SRL 6-50).
If the connecting lines for steam ≥ 40 mm and water ≥ 100 mm, the installation is considered to be
internal. In this case the rinsing processes do not have to be monitored.
An autmatic self-testing routine monitors the safety functions of the level switch. In the event of a
malfunction the control circuit opens instantaneously and switches off e. g. the feedwater supply.
Alarm and malfunction messages are indicated by LEDs, and the signal output is instantaneously
energized.
An alarm can be simulated by pressing the test button.
During the rinsing process the water level cannot be measured in the level pot for 5
The level switch therefore bypasses the level electrode and monitors the rinsing and bypass time
NRG 16-51 NRG 17-51 NRG 19-51
NRG 16-51
NRG 16-12
NRG 17-51
NRG 17-12
NRG 19-51
NRG 19-12
Note
n A high level alarm prevents the water level from exceeding the preset max. liquid
level (HW). For this purpose it can, for instance, interrupt the feedwater supply. If the
interruption of the feedwater supply endangers the heating surfaces in the feedwater
preheater (economizer), the heating must be switched off, too.
Directives and Standards
Pressure Equipment Directive (PED) 97/23/EC
The level switch NRS 1-51 in conjunction with level electrode NRG 1...-51 is EC type approved
according to EN 12952/EN 12953. These Directives state, among other things, the requirements made
on limiting systems and equipment for steam boiler plants and (pressurised) hot-water installations.
Functional Safety acc. to IEC 61508
The level switch NRS 1-51 is certified acc. to IEC 61508 only if used in combination with level elec
trode NRG 1...-51. This standard describes the functional safety of safety-related electrical/electronic/
programmable electronic systems.
The equipment combination NRG 1...-51 + NRS 1-51 corresponds to a type B subsystem with Safety
Integrity Level (SIL) 3.
VdTÜV Bulletin “Wasserstand 100” (= Water Level 100)
The level switch NRS 1-51 in conjunction with the level electrodes NRG 1...-51 and NRG 1...-12 is type
approved according to the VdTÜV Bulletin "Water Level 100".
The VdTÜV Bulletin “Wasserstand (=Water Level) 100” specifies the requirements made on water level
control and limiting equipment for boilers.
LV (Low Voltage) Directive and EMC (Electromagnetic Compatibility)
The level switch NRS 1-51 meets the requirements of the Low Voltage Directive 2006/95/EC and the
EMC Directive 2004/108/EC.
ATEX (Atmosphère Explosible)
According to the European Directive 94/9/EC the level switch NRS 1-51 must
explosive areas.
Note
The level electrodes NRG 1...-51, NRG 1...-12 are simple items of electrical equipment
as specified in EN 60079-11 section 5.7. According to the European Directive 94/9/EC
the equipment must be equipped with approved Zener barriers if used in potentially
explosive areas. 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.
Note that the requirements of the IEC 61508 are not met if the NRG 1...-51,
NRG 1...-12 + Zener barriers + NRS 1-51 are interconnected!
not be used in potentially
-
5
6
Functional Safety acc. to IEC 61508
Safety characteristics of the subsystem NRG 1...-51 / NRS 1-51
The level switch NRS 1-51 is certified acc. to IEC 61508 only if used in combination with level electrodes
NRG 1...-51.
The equipment combination NRG 1...-51 / NRS 1-51 corresponds to a type B subsystem with Safety
Integrity Level (SIL) 3. Type B means that the behaviour under fault conditions of the used components
cannot be completely determined. The functional safety of the equipment combination refers to the
detection and evaluation of the water level and, as a consequence, the contact position of the output
relays.
The design of the equipment combination NRG 1...-51 / NRS 1-51 corresponds to the architecture
1oo2 D. This architecture consists of two channels that detect and diagnose faults in each other. If a fault
is detected, the equipment combination NRG 1...-51 / NRS 1-51 will go to the safe state, which means
that the contacts of both output relays will open the control circuit.
Safety characteristics
General 3 1oo2 D 20 20
Level switch NRS 1-51 alone 98.54 % 1.18 x 10
Level switch NRS 1-51 in conjunction with one
level electrode NRG 1...-51
Fig. 1
Terms and abbreviations
Terms
Abbreviations
Safety Integrity Level
SIL
Lifetime (a) Functional safety: Lifetime in years
Safe Failure Fraction
SFF
Probability Failure per Demand
(Low Demand)
PFD
av
Probability Failure per Hour
PFH
av
λ
DU
Classification of the Safety Integrity Level acc. to IEC 61508
Percentage of failures without the potential to put the safety-related system into
a dangerous state
Average probability of failure on demand for low demand mode (once a year)
Probability of failure per hour
Failure rate for all dangerous undetected failures (per hour) of a channel of a
subsystem
Fig. 2
SIL Architecture Lifetime
SFF PFD
98.17 % 1.69 x 10
av
-4
3.73 x 10
-4
4.54 x 10
Description
PFH
(a)
Proof Test
Interval (a)
av
-8
-8
λ
DU
7.33 x 10
9.33 x 10
-8
/h
-8
/h
Functional Safety acc. to IEC 61508 – continued –
Determination of the Safety Integrity Level (SIL) for safety-related systems
Level electrode, level switch and actuators (auxiliary contactors in control circuit) are subsystems and
together constitute a safety-related system that executes a safety function.
The specification of the safety-related characteristics Fig. 1 refers to the level electrode and the level
switch including the output contacts. The actuator (e. g. an auxiliary contactor in the control circuit) is
installation specific and, according to IEC 61508, must be considered separately for the whole safetyrelated system.
Table Fig. 3 shows the dependence of the Safety Integrity Level (SIL) on the average probability of failure
on demand of a safety function for the whole safety-related system (PFD
is here considered for a water level limiter, which means that the frequency of demands for operation of
the safety-related system is no greater than one per year.
). The “Low demand mode”
sys
Low demand mode PFD
-5
... < 10
≥ 10
-4
... < 10
≥ 10
-3
... < 10
≥ 10
-2
... < 10
≥ 10
Safety Integrity Level
sys
-4
-3
-2
-1
(SIL)
4
3
2
1
Fig. 3
The table in Fig. 4 indicates the attainable Safety Integrity Level (SIL) as a function of the Safe Failure
Fraction (SFF) and the Hardware Fault Tolerance (HFT) for safety-related systems.
Hardware Fault Tolerance (HFT) for type B
0 1 2
SIL 1 SIL 2
SIL 1 SIL 2
SIL 2
SIL 3 SIL 4 90 % – < 99 %
SIL 3 60 % – < 90 %
SIL 3 SIL 4 SIL 4 ≥ 99 %
Safe Failure Fraction
(SFF)
< 60 %
Fig. 4
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8
Technical Data
NRS 1-51
Supply:
Mains voltage
24 VDC +/– 20%, 0.3 A or 100 – 240 VAC +10/–15 %, 47 – 63 Hz, 0.2 A
External fuse
0.5 A (semi-delay)
Power consumption
7 VA
Inputs:
Electrical connection of level electrode
1 input for level electrode NRG 1...-51, NRG 1...-12, 4-poles with screen
Sensitivity 0.5 μS/cm or 10 μS/cm (at 25 °C).
Stand-by input
1 volt-free input, 18-36 VDC, for monitoring the purging and bypass time.
Max. bypass time: 5 minutes.
Outputs:
Control circuit
2 volt-free make contacts, 24 V DC – 250 V AC, max. 6 A (resistive/inductive),
Contact material AgNi.
Delay of response: 3 seconds.
Provide inductive loads with RC combinations according to manufacturer's specification to ensure
interference suppression.
Signal output
1 volt-free output for instantaneous external signalling, 24 – 230 V AC/DC, max. 100 mA.
Indicators and adjustors
2 buttons for test and diagnosis,
2 red/green LEDs for indicating the operating mode and alarm.
3 red LEDs for diagnosis.
Housing
Housing material: base: polycarbonate, black; front: polycarbonate, grey.
Cross section of connection: 1 x 4.0 mm
1 x 2.5 mm
2 x 1.4 mm
2
per stranded wire with sleeve to DIN 46228 or
2
per stranded wire with sleeve to DIN 46228; terminal strips can be detached
2
solid per wire or
Fixing of housing: Mounting clip on supporting rail TH 35, EN 60715
Electrical safety
Degree of contamination: 2, overvoltage category III to EN 61010-01.
Protection
Housing: IP 40 to EN 60529
Terminal strip: IP 20 to EN 60529
Weight
approx. 0.5 kg
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