INSTRUCTION MANUAL
NI-205WE
Rev. 3 12/16
2 of 8
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
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).
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 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
Hazardous area
Categories
according to
2014/34/EU
directive
EPL
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
