WIKA APA SERIES, APW10UG, APW10US, APW10UO, APW10UN Instruction Manual

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INSTRUCTION MANUAL

NI-205WE

Rev. 3 12/16

WEATHERPROOF AND INTRINSICALLY SAFE: MODEL APW FLAMEPROOF: MODEL APA

Versions APWH, APWL

A pressure attachment
B cable entry

ersions APW10

ABSOLUTE PRESSURE

Versions APAH, APAL

WEIGHT 5,5 kg
(dimensions in mm)

vacuum attachment

B cable entry

ersions APA10

SWITCHES

WEIGHT 6,5 kg
(dimensions in mm)

A pressure attachment
B cable entry
For surface mounting use four screws M6.

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.

SAFETY INSTRUCTIONS FOR USE IN HAZARDOUS ATMOSPHERES.

RECOMMENDATIONS FOR PRESSURE SWITCH SAFE USE.

WEIGHT 8,2 kg
(dimensions in mm)

A vacuum attachment
B cable entry

WEIGHT 10 kg
(dimensions in mm)

RELATED DOCUMENT

To authentified document with certificate

N° IECEx PRE 16.0068X
N° IECEx PRE 16.0074X

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
other than that for which it is supplied.

ALEXANDER WIEGAND SE &Co

and may not be reproduced in any form, nor used for any pur-pose

INSTRUCTION MANUAL

1 GENERAL NOTES

1.1 FOREWORD

APW and APA models were designed for applications
where absolute-zero rather than atmospheric set point
value is required (see fig.1)

Fig. 1 - Pressure designation

NI-205WE

Rev. 3 12/16

Therefore, in case it does, suitable measures (protection
against heat radiation, fluid separators, cooling coils,
heated lockers) must be taken. Process fluid or its solid
particles must not however go inside instrument
chambers.

2 OPERATING PRINCIPLE

The process pressure, acting on the diaphragm sensitive
element, that has got absolute vacuum as reference
pressure, 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 MODEL CODE

See Annex 1

4 IDENTIFICATION PLATE AND MARKINGS

The instrument is fitted with a metal plate bearing all its
functional characteristics and in case of flame proof or
intrinsic safety execution also the markings prescribed by
standard IEC/EN 60079-0. Fig.2 shows the plate mounted
on flame proof instruments.

Fig. 2 - Flame proof instruments plate

1.2 RANGE CHOICE

The wrong choice of a models or a version, 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.

1.3 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.

1.4 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.).

1.5 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 -40° to +60°C).

1 Notified body that issued the type certificate and number of said

certificate.

2 CE marking and identification number of the notified body

responsible for production surveillance.

3 Apparatus classification according to ATEX 2014/34/EU

directive.

4 Type of protection and ambient temperature limits of operation.

The following table gives the relationship between
hazardous areas, Atex Categories and Equipment
Protection Level (EPL) listed on the flameproof instrument
nameplate

Categories

Hazardous area

Gas, vapours, fog Zone 0 1G Ga

Gas, vapours, fog Zone 1 2G or 1G Gb or Ga

Gas, vapours, fog Zone 2 3G, 2G or 1G Gc, Gb or Ga

Dust Zone 20 1D Da

Dust Zone 21 2D or 1D Db or Da

Dust Zone 22 3D, 2D or 1D Dc, Db or Da

according to

2014/34/EU

directive

EPL

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INSTRUCTION MANUAL

5 SET POINT REGULATION

Each microswitch is independent and can be regulated by
means of a screw (for adjustment to snap 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 calibration). The instrument is supplied with
alabel 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 label.

If the instrument has been ordered with a specific
calibration, check the calibration values marked on the
relevant label, prior to installation.

The position of the adjustment screws is given in figure 3.
Fig. 2 - Electrical connections and adjustment screws

NI-205WE

Rev. 3 12/16

Fig. 5 - Weatherproof pressure switch blocking and
plumbing device

a - Plumbing wire
b - Plumbing
c - Blocking nut

6.1.2 Flameproof pressure switches (Models APA)
CAUTION: do not open the cover of flameproof pressure

switches (Models APA) when energized, in explosive
atmospheres.

Loosen the locking headless screw situated on the cover
using a 1,5 hexagonal key then unscrew the cover (fig.6).
Remove the internal blocking device inserted on the
closure plugs and slide out the plugs.

Fig. 6 - Flameproof pressure switch blocking device

d - Blocking bracket
e - Adjustment screw access
plate

1 - Microswitch 2 set point calibration screw
2 - Microswitch 1 set point calibration screw
3 - Terminal block

4 - Electrical connection identification plate

Microswitch electrical circuit: State of the contacts at zero
absolute pressure

Designation of the contacts:

The effect that the direction of rotation of the adjustment
screws has is described on the label.

6 SET POINT CALIBRATION

In order to proceed with the calibration and the periodical
functional verification of the instrument a suitable
calibration circuit (fig.4) and an adequate pressure
source is required. The test instrument should have a
measurement range approximately equal to or slightly
wider than the pressure switch range and should have an
accuracy consistent with the precision required to
calibrate the set point.

Fig 4 - Calibration circuit

PS - Pressure switch
CA - Test pressure gauge for

absolute pressure

6.1 PRELIMINARY OPERATIONS

6.1.1 Weatherproof pressure switches (Models APW)

Remove the blocking device fixed to the side of the
instrument case and the adjustment screw access
plate(fig. 59. Remove the cover by rotating it in an
anticlockwise direction.

C - common
NA - Normally open
NC - Normally closed

V1 - Inlet valve
V2 - Outlet valve
P - Absolute pressure source

6.2 CALIBRATION CIRCUIT AND OPERATIONS

Prepare the control circuit as indicated in Fig.4.
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.

• If the circuit is open at the working pressure, the switch
closes the circuit as the pressure decreases when the
desired value is reached.
The pressure switch must be mounted in the normal
installation position, i.e. with the pressure connection
pointing downwards.
Avoid forcing the elastic support of the microswitch by
hand or with tools. This could affect the instrument
functioning.

CAUTION: if the switch is of the kind with adjustable dead
band (letter R of contacts code) before proceeding with
the following operations it is necessary to proceed with
the adjustment of the dead band.

Increase the pressure in the circuit up to the desired set
point value for the first microswitch.

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