Kobold NBK-RA User manual
Operating Instructions
for
Limit switch
Model: NBK-RA
NBK-RA
page 2 NBK-RA K01/0823
1. Contents
1.Contents ........................................................................................................ 2
2.Note .............................................................................................................. 3
3.Instrument Inspection .................................................................................... 3
4.Regulation Use ............................................................................................. 4
4.1Electrical limit switch ............................................................................ 4
5.Operating Principle ........................................................................................ 5
6.Mechanical Connection ................................................................................. 6
7.Electrical Connection .................................................................................... 7
8.Commissioning.............................................................................................. 8
9.Technical Information .................................................................................... 9
10.Order Codes ............................................................................................... 10
11.Illustrations .................................................................................................. 11
12.Disposal ...................................................................................................... 12
13.EU Declaration of Conformance ................................................................. 13
14.Type Examination Certificate ...................................................................... 14
Manufactured and sold by:
Kobold Messring GmbH
Nordring 22-24
D-65719 Hofheim
Tel.: +49 (0)6192-2990
Fax: +49(0)6192-23398
E-Mail: [email protected]
Internet: www.kobold.com
NBK-RA
NBK-RA K01/0823 page 3
2. Note
Please read these operating instructions before unpacking and putting the unit
into operation. Follow the instructions precisely as described herein.
The instruction manuals on our website www.kobold.com are always for currently
manufactured version of our products. Due to technical changes, the instruction
manuals available online may not always correspond to the product version you
have purchased. If you need an instruction manual that corresponds to the
purchased product version, you can request it from us free of charge by email
([email protected]) in PDF format, specifying the relevant invoice number and
serial number. If you wish, the operating instructions can also be sent to you by
post in paper form against an applicable postage fee.
The devices are only to be used, maintained and serviced by persons familiar
with these operating instructions and in accordance with local regulations
applying to Health & Safety and prevention of accidents.
3. Instrument Inspection
Instruments are inspected before shipping and sent out in perfect condition.
Should damage to a device be visible, we recommend a thorough inspection of
the delivery packaging. In case of damage, please inform your parcel service /
forwarding agent immediately, since they are responsible for damages during
transit.
Scope of delivery:
The standard delivery includes:
Electrical Limit Switch Model: NBK-RA
NBK-RA
page 4 NBK-RA K01/0823
4. Regulation Use
Any use of the device which exceeds the manufacturer’s specification may
invalidate its warranty. Therefore, any resulting damage is not the responsibility of
the manufacturer. The user assumes all risk for such usage.
The Limit Switches for the NBK Bypass Level Indicators are used for continuos
measuring, display and monitoring of liquids in tanks or vessels. Depending on
the design the limit switches are suitable for applications with a higher operating
temperature or for the use in hazardous areas.
4.1 Electrical limit switch
For ATEX applications NBK-RA: Bistable changeover contact as an encapsulated
proximity switch fitted in metallic cast housing with 3 m connection cable.
ATEX-marking for contact NBK-RA (encapsulated version):
II 2G Ex mb IIC T6 / T5 Gb
II 2D Ex mb IIIC IP67 T 105 °C Db
Use the contacts appropriate and as intended.
Make sure that only accessories are used in hazardous areas that meet
all the requirements of the European directives and national legislation.
The contacts NBK-RA with ATEX approval meet the requirements of category
2 GD. The proximity switches with ATEX approval are used in the following
zones:
2G in zone 1
3G in zone 2
2D in zone 21
3D in zone 22
NBK-RA
NBK-RA K01/0823 page 5
5. Operating Principle
Kobold Bypass Limit Transmitter are used for the monitoring of limit values in
tanks or vessels. They are firmly attached with mounting plates and ribbon
clamps to the Bypass Level Indicator, model NBK, and can be moved to any
position on the bypass-tube within the measuring length. The reed-contacts in the
limit switches react bistable and they are switched by the magnetic float inside
the NBK tube as passing by. One or more limit switches can be mounted on the
bypass.
NBK-RA
page 6 NBK-RA K01/0823
6. Mechanical Connection
Mount and tighten the reed switch (NBK-RA) - if available - on the bypass tube
at the opposite side of the roller indicator with the provided ribbon clamps (ex
contact: two ribbon clamps). The height of the switch contacts may be selected at
will. The cable connection must point downwards. The switch must be attached
close to the bypass tube.
Due to technical adaptations, it may come to malfunctions, when installing new
contacts in an existing plant. If the contact does not switch during the float passes
by, the preassembled spacer (plastic) must be removed.
NBK-RA
NBK-RA
NBK-RA K01/0823 page 7
A
TE
X
- contact
brown
blue
black
7. Electrical Connection
Limit switch NBK-R, NBK-RM, NBK-RT, NBK-RA
Attention!
Observe the allowed electrical ratings for the limit switch.
Maximum values NBK-RA
ATEX-contact
Switching capacity: 45 W/VA
Switching current: 0,6 A
Switching voltage: 230 VAC/DC
Note to NBK-RA:
Protect the circuit of the limit contact with a fuse. This fuse
must tolerate the permitted nominal current of the
switching contact and must have a deactivating ability
according to the possible short circuit current of the power
system at the place of installation. The contact is activated
by the North Pole of a magnet and deactivated by its South
Pole.
NBK-RA
NBK-RA
page 8 NBK-RA K01/0823
8. Commissioning
Commissioning of the electrical reed switch
Function of switches
All switches have three connection poles (black, blue and brown).
The black wire is the common pole for both switching functions (N/C and N/O
contact).
The float must pass the switch once in both directions so that the switching
function is in line with the terminal connection diagram and table below.
These instructions are often ignored when an alarm lamp is connected directly
with the result that the alarm lamp incorrectly indicates a fault.
When the switch has been passed, it is ready for operation and requires no
maintenance.
black / blue black / brown
float above open closed
float below closed open
Hysteresis
Hysteresis is the difference between contact closing
and opening points. A hysteresis of approximately
15 mm float travel is achieved by factory tuning of the
float magnet and contact strength.
NBK-RA
NBK-RA K01/0823 page 9
9. Technical Information
ATEX limit switch, model NBK-RA
Contact operation: bistable changeover contact
encapsulated
Switching hysteresis: approximately 15 mm
Max. switching capacity: 45 VA, 230 VAC/DC, 0,6 A
Temperature class: T6 / T5
Max. medium temperature: 70 °C / 85 °C
Connection: 3 m PVC cable
Housing: metallic, cast (GD-ZN Al 4 Cu1)
Protection: IP 67
ATEX-marking: II 2G Ex mb IIC T6/T5 Gb
II 2D Ex mb IIIC IP67 T 105 °C Db
NBK-RA
page 10 NBK-RA K01/0823
10. Order Codes
NBK-RA
ATEX-limit contact, encapsulated,
II 2G Ex mb IIC T6/T5 Gb
II 2D Ex mb IIIC IP67 T 105 °C Db
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