WIKA TXA User Manual

INSTRUCTION MANUAL

NI-492E

REV. 0 01/05

TEMPERATURE SWITCHES SERIES TXS,TXN,TXA

WEATHERPROOF (Series TXS) AND FLAMEPROOF (Series TXA, TXN)

INSTRUMENT STANDARD INSTRUMENT WITH JUNCTION BOX

Stems Type C-Q-R Stem Type B

Stem Type B: Y =125mm ; X = 50mm Stem Type Q: K = 5m ; Y max.=900mm
Stem Type C: K = 2m ; Y max.=350mm Stem Type R: K = 10m ;Y max.=1800mm

WEIGHT 0,4kg Dimensions in mm WEIGHT 1kg 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
2 - OPERATING PRINCIPLE
3 - IDENTIFICATION PLATE AND MARKINGS
4 - SPECIAL CONDITIONS FOR SAFETY USE (X)
5 - SET POINT ADJUSTMENT
6 - SET POINT CALIBRATION
7 - INSTRUMENT PLUMBING
8 - MOUNTING AND CONNECTIONS
9 - PUTTING INTO OPERATION
10 - FUNCTIONAL VERIFICATION
11 - TROUBLE SHOOTING
12 - STOPPING AND DISMOUNTING
13 - DEMOLITION
14 - NOTE FOR INSTALLATION

SAFETY INSTRUCTIONS FOR USE IN EXPLOSIVE ATMOSPHERES

RECOMMENDATIONS FOR THE SAFE USE OF THE INSTRUMENT

DOCUMENT CORRELATED

to document authenticated with certificates

N° CESI 05 ATEX 002X

N° CESI 05 ATEX 003

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 for which it is supplied.

INSTRUCTION MANUAL

1 - GENERAL

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 follow the indications given in this manual can cause
damage to the instrument, the environment and persons.

1.2 ALLOWED OVERRANGES

Temperatures exceeding the working range can be occasionally
tolerated provided they remain within the limits stated for the
instrument (proof temperature). Continuous temperatures
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 data plate must not be exceeded: transitory
overranges can have a destructive effect on the switch.

1.3 TEMPERATURES

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°C to +85°C). Therefore, in case it does,
suitable measures (protection against heat radiation, fluid
separators, cooling coils, heated lockers), aimed at limiting the
value, must be taken.

2 - OPERATING PRINCIPLE

The operating principle is based on a pressure measuring
element connected via a capillary tubing with a temperature
sensitive bulb. The system is partially filled with a volatile liquid
generating a pressure that is a non linear function of the bulb
temperature; this pressure is applied to a diaphragm acting on a
stiff disc with a force directly proportional to the bulb temperature.
The force is contrasted by an helical spring loaded by a suitable
bush. When the force balance point is exceeded, the stiff disc
shifts and, by means of a rigid rod, actuates one or two
simultaneous release electric microswitches. The
microswitches are of the snap acting type with automatic reset.
When the pressure moves away from the set values, returning
towards the normal values, the switch is reset.

3 - NAMEPLATE AND MARKINGS

The instrument is fitted with a metal plate bearing all its functional
characteristics and – in case of explosionproof execution (Series
TXA and TXN) – also the markings prescribed by standard EN
50014 and EN 50281-1-1. Fig. 1 shows the nameplate mounted
on explosionproof instruments.

Fig. 1 - Nameplate, explosionproof instruments

1 CE marking and identification number of the notified body

responsible for production surveillance.
2 Apparatus classification according to ATEX 94/9 CE directive.
3 Notified body that issued the type certificate and number of said

certificate.
4 Mode of protection and operating ambient temperature limits.

4 - SPECIAL CONDITIONS FOR SAFE USE (X)

Explosionproof instruments (Series TXA and TXN) installed
without a junction box require an electric connection, suitable for
the mode of protection choosen, at the free end of the cable (see
Point 8).

NI-492E

REV. 5 11/02

5 - SET POINT ADJUSTMENT

The load of the helical spring can be adjusted by means of the
bush 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 initial range value if this is above
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 using a
suitable indelible ink pen.

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.

The position of the adjusting bush is given in Fig. 2.

Fig. 2 - Adjusting bush and plumbing

c Adjustment slot

cover

d Stainless steel

wire

e Sealing lead
f Adjusting bush

The effect of the sense of rotation of the adjusting bush is shown
on the slot cover. Rotate the bush by inserting a 3mm dia. rod or
drill into the holes on the bush itself.

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 temperature source are
required.
Wiring is to be carried out as shown in Fig. 3 and on the slot
cover.

Fig. 3 - Electric wiring

GDN - Ground internal : leadwire yellow/green
C - Common : leadwire brown
NA - Normally open : leadwire blue
NC - Normally closed : leadwire black
C - Common : leadwire grey
NA - Normally open : leadwire red
NC - Normally closed : leadwire white

Microswitch internal wiring. Contacts status with bulb at initial
range value.

Micro 1

Micro 2

C - Common
NA - Normally open
NC - Normally closed