WIKA BWX User Manual
A
A
INSTRUCTION MANUAL
Rev. 1 12/02
BOURDON TUBE PRESSURE SWITCHES
WEATHERPROOF: SERIES BW EXPLOSIONPROOF: SERIES BAX
B
NI-222E
B
A pressure attachment
B cable entry
WEIGHT 2 kg dimensions in mm WEIGHT 3,7 kg dimensions in mm
NOTE: dimensions and weights are not binding unless released on certified drawings.
CAUTION
• Before installing, using or carrying out maintenance on the instrument it is necessary to read and understand the
indications given in the attached Instruction Manual.
• The instrument must only be installed and maintained by qualified personnel.
• INSTALLATION IS TO BE CARRIED OUT ONLY AFTER CHECKING THAT INSTRUMENT CHARACTERISTICS
ARE CONSISTENT WITH PROCESS AND PLANT REQUIREMENTS.
• The functional features of the instrument and its degree of protection are shown on the identification plate fixed to the
case.
CONTENTS:
1 - GENERAL NOTES
2 - OPERATING PRINCIPLE
3 - IDENTIFICATION PLATE AND MARKINGS
4 - SET POINT REGULATION
5 - SET POINT CALIBRATION
6 - MOUNTING AND CONNECTIONS
7 - INSTRUMENT PLUMBING
8 - PUTTING INTO OPERATION
9 - FUNCTIONAL VERIFICATION
10 - TROUBLESHOOTING
11 - STOPPING AND DISMOUNTING
12 - DEMOLITION
SAFETY INSTRUCTIONS FOR USE IN HAZARDOUS ATMOSPHERES.
RECOMMENDATIONS FOR PRESSURE SWITCH SAFE USE.
A pressure attachment
B cable entry
RELATED DOCUMENT
To authentified document with certificate
N° CESI 03 ATEX 005
All data, statements and recommendations supplied with this manual are based on information believed by us to be
reliable. As the conditions of effective use are beyond our control, our products are sold under the condition that the
user himself evaluates such conditions before following our recommendations for the purpose or use foreseen by him.
The present document is the property of ETTORE CELLA SPA and may not be reproduced in any form, nor used for
any purpose other than that for which it is supplied.
NI-222E
INSTRUCTION MANUAL
Rev. 1 12/02
1 - GENERAL NOTES
1.1 FOREWORD
The wrong choice of a series or a model, as well as the
incorrect installation, lead to malfunction and reduce
instrument life.
Failure to abide by the indications given in this manual
can cause damage to the instrument, the environment
and persons.
1.2 ALLOWED OVERRANGE
Pressure exceeding the working range can be occasionally tolerated provided they remain within the limits
stated in the instrument features (vacuum or proof pressure). Continuous pressures exceeding the working
range can be applied to the instrument provided they are
clearly stated in the instrument features. The current and
voltage values stated in the technical specifications and
ratings must not be exceeded. Transitory overranges
can have a destructive effect on the switch.
1.3 MECHANICAL VIBRATIONS
Can generally lead to the wearing of some parts of the
instrument or cause false actuation. It is therefore recommended that the instrument be installed in a place
where there are no vibrations. In cases where this is
impossible it is a good idea to take measures to lessen
the effects (elastic supports, installation with the peg of
the microswitch positioned at right angles to the vibration
plane, etc.).
1.4 TEMPERATURE
Due to the temperature of both the environment and the
process fluid, the temperature of the instrument could
exceed the allowed limits (normally from -20° to +70°C).
Therefore, in case it does, suitable measures (protection
against heat radiation, fluid separators, cooling coils,
heated lockers) must be taken.
2 - OPERATING PRINCIPLE
The pressure, acting on the sensitive element (Bourdon
tube), determines its elastic deformation which is used to
activate one or two electric microswitches regulated at
set point values. The microswitches are of the rapid
release type with automatic rearm. When the pressure
moves away from the set values, returning towards the
normal values, the switch is rearmed. The differential
gap (difference between the set point value and the reset
value) can be set or adjustable (letter R in the contact
codes).
3 - IDENTIFICATION PLATE AND MARKINGS
The instrument is fitted with a metal plate bearing all its
functional characteristics and – in case of explosionproof
execution (Series BAX) – also the markings prescribed
by standard CEI EN 50014. Fig. 2 shows the plate
mounted on explosionproof instruments.
Fig. 1 - Explosionproof instruments plate
1 CE marking and identification number of the notified body
responsible for production surveillance.
2 Apparatus classification according to ATEX 94/9 CE direc-
tive.
3 Type of protection and ambient temperature limits of opera-
tion.
4 Notified body that issued the type certificate and number of
said certificate.
4 - SET POINT REGULATION
Each microswitch is independent and can be regulated
by means of a screw (for adjustment) in such a way that
it is released when the pressure reaches (increasing or
decreasing) the desired value (set point).
The instrument is usually supplied with the switches set
at the setting range value nearest to zero (factory cali-
bration).
The instrument is supplied with an adhesive rating plate
showing the set point calibration value. With factory
calibration the values are not indicated on the ratings as
these are temporary and will be modified with the definitive values.
Prior to installation the instrument must be calibrated
and the definitive calibration values written on the adhesive rating plate using a suitable indelible ink pen.
If the instrument has been ordered with a specific cali-
bration, it is a good rule to check the calibration values
marked on the relevant adhesive label, prior to installation.
The position of the adjustment screws is given in figure
The effect that the direction of rotation of the adjustment
screws has is described on the adhesive plate.
NI-222E
INSTRUCTION MANUAL
Rev. 1 12/02
Fig. 2 -
One contact instruments
1 - Microswitch set point calibration screws
3 - Terminal block
4 - Electrical connection identification plate
5 - SET POINT CALIBRATION
In order to proceed with the calibration and the periodical
functional verification of the instrument a suitable cali-
bration circuit (fig. 5) and an adequate pressure source
is required.
5.1 PRELIMINARY OPERATIONS
Weatherproof pressure switches (BWX)
Remove the blocking device fixed to the side of the instrument case and the adjustment screw access plate
(Fig. 3). Remove the cover by rotating it in an anticlockwise direction.
Fig. 3 - Weatherproof pressure switch blocking device -
Electrical connections and adjustment screws
Two contact instruments
1 - Microswitch 2 set point calibration screws
2 - Microswitch 1 set point calibration screws
3 - Terminal block
4 - Electrical connection identification plate
Explosionproof pressure switches (BAX) (Fig. 4)
CAUTION: do not open the cover of explosionproof
pressure switches (Series BAX) when energized, in
explosive atmospheres.
Loosen the locking headless screw situated on the
cover using a 1,5 hexagonal key then unscrew the cover.
Remove the internal blocking device inserted on the
closure plugs and slide out the plugs.
Fig. 4 -
Explosionproof pressure switch blocking device
Microswitch electrical circuit
State of the contacts at atmospheric pressure
Designation of the contacts:
C - common
NA - Normally open
NC - Normally closed
a - Plumbing wire
b - Plumbing
c - Blocking nut
d - Blocking bracket
e - Adjustment screw access
plate
5.2 CALIBRATION CIRCUIT AND OPERATIONS
Prepare the control circuit as indicated in Fig.5.
The warning lamps should be connected to contact 1 or
2 in the NO or NC position according to the required
contact action.
Connection of C and NO terminals
• If the circuit is open at the working pressure, the
switch closes the circuit as the pressure increases
when the desired value is reached.
• If the circuit is closed at the working pressure, the
switch opens the circuit as the pressure decreases
when the desired value is reached.
Connection of C and NC terminals
• If the circuit is closed at the working pressure, the
switch opens the circuit as the pressure increases
when the desired value is reached.
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