INSTRUCTION MANUAL
NI-492WE
Rev.4 05/18
2 of 7
1 - GENERAL
1.1 FOREWORD
The wrong choice of a models or a version, as well as the
incorrect installation, lead to malfunction and reduce instrument
life. Failure to follow the indications given in this manual can
cause damage to the instrument, the environment and persons.
1.2 ALLOWED OVERRANGES
Temperature exceeding the working range can be
allowed only
for testing proposal
up to the proof temperature.
Continuous
temperature exceeding the (adjustable) “RANGE* (see fig 1) can
be applied to the instrument, provided they are clearly stated in
the instrument features (see fig.1, “MAX TEMPERATURE”).
The current and voltage values stated in the technical
specifications and data plate must
not
be exceeded: transitory
overranges can have a destructive effect on the switch.
1.3 TEMPERATURES
The temperature of the instrument is influenced by the
environmental and process temperature. Special attention must
be taken to avoid the exceeding of the limits specified in table 1
and 2.
For the instrument version TX**B* (stem for direct mounting) the
following table is applicable
Table 1 – Temperature conditions
Temp.
Classification
Ambient
temperature
range (Tamb)
Max
working
temperature
(T max.)
Max electrical
rating
(resistive load)
T6
-50 … +60 °C
Shall not exceed the
maximum
temperature specified
on the nameplate
(see fig.1 item 5).
5A@24V d.c.;
5A@250V a.c.
See nameplate of
the instrument
(electrical rating)
T5
T4
-50 … +85 °C
T3
T2
T1
For the instrument versions TX**C*, TX**Q*, TX**R* (stem for
remote mounting) and TX**S* (helical bulb for ambient
temperature) the following table is applicable
Table 2 – Temperature conditions
Temperature
Classification
Ambient
temperature
range
(Tamb)
Max electrical rating
(resistive load)
T6
-50..+60 °C
5A@24V d.c.; 5A@250V a.c.
See nameplate of the instrument
(electrical rating)
T5
T4
-50..+85 °C
T3
T2
T1
2 - OPERATING PRINCIPLE
The operating principle is based on a pressure measuring
element, connected via a capillary tube to a bulb. This system is
partially filled with a volatile liquid, the residual free volume being
filled by its saturated vapour. In this system a pressure is
generated which is a non-linear function of bulb temperature; this
pressure acts on a stainless steel diaphragm which applies a
force to a stiff disc; this force is directly proportional to the
temperature value to which the bulb is submitted and is
contrasted by an compression spring charged by a suitable bush.
When the force balance point is exceeded, the stiff disc shifts
and, by means of a rigid rod,
activates one or two
simultaneous
release
electric
microswitches
.
The
microswitches are of the rapid release type with automatic rearm.
When the temperature moves away from the set values,
returning towards the normal values, the switch is rearmed.
3 - MODEL CODE
See Annex 1
4 - NAMEPLATE AND MARKINGS
The instrument is fitted with a metal plate bearing all its functional
characteristics and in case of flameproof or intrinsic safety
execution, also the markings prescribed by standard IEC/EN
60079-0. Fig.1 shows the plate mounted on flameproof
instruments.
Fig. 1 - Flameproof 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.
5 Max working temperature
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 (ATEX)
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
5 - SPECIAL CONDITIONS FOR SAFE USE (X)
The instrument cannot be repaired (see also throubleshooting).
Should the instrument be installed without a junction box require
an electric connection suitable for the mode of protection chosen
at the free end of the cable.
Should the instrument be installed in mines (Group I) the elettrical
connection has require to be protected by chemical agents.
Therefore a mounting with cable protected by tubing is
mandatory.
6 - SET POINT ADJUSTMENT
The compression of the spring can be regulated by means of the
bush (for adjustment) in such a way that the switch is released
when the temperature reaches (either increasing or decreasing)
the desired value (set point). The instrument is usually supplied
with the switches set at 0°C or at the lowest setting range value
if this is higher than 0°C
(factory calibration)
.
The instrument is supplied with an adhesive label showing the
set point calibration value. With
factory
calibration
the values
are not indicated on the label 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
, it
is a good rule to check the calibration values marked on the
relevant adhesive label, prior to installation.
