INSTRUCTION MANUAL
NI-401E
Rev. 3 07/99
TEMPERATURE SWITCHES
WEATHERPROOF: SERIES TWG EXPLOSIONPROOF: SERIES TAG
One contact
Stem type “B” Stem type “C” Stem type “ F”
A = bulb connection
B = cable entry
PESO 2,1 kg dimensions in mm PESO 2,9 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 must only be carried out following verification of the congruity of the instrument features with the plant
and process 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 - SET POINT REGULATION
4 - SET POINT CALIBRATION
5 - MOUNTING AND CONNECTIONS
6 - INSTRUMENT PLUMBING
X = Bulb sensitive portion
Y = Insertion length
K = Capillary length
A = bulb connection
B = cable entry
7 - PUTTING INTO OPERATION
8 - FUNCTIONAL VERIFICATION
9 - TROUBLESHOOTING
10 - STOPPING AND DISMOUNTING
11 - DEMOLITION
Two contacts
X = Bulb sensitive portion
Y = Insertion length
K = Capillary length
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.
INSTRUCTION MANUAL
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 follow the indications given in this
manual can cause damage to the instrument, the
environment and persons.
1.2 ALLOWED OVERRANGE
Temperatures exceeding the working range can be
occasionally tolerated provided they remain within the
limits stated in the instrument features (vacuum or 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 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 advisable to take measures to lessen the
effects (elastic supports, installation with the pin 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, heated cabinets) must be taken.
2 - OPERATING PRINCIPLE
fig. 1 - Electrical connections and adjustment screws
One contact instruments Two contact instruments
The thermometric bulb is constituted by a rigid constantvolume container. It is connected via capillary tubing to a
pressure measuring element (bourdon tube). This system
is filled with gas, and its absolute pressure is proportional
to absolute temperature (Charles’ law). As a consequence,
any change in bulb temperature causes a change in gas
pressure acting on sensible element, causing its free tip to
undergo an elastic deflection which is used to actuate one
or two electrical microswitches adjusted at prefixed set
point values.
3 - SET POINT REGULATION
3.1 Each microswitch is independent and can be
regulated by means of a screw (for adjustment) in such a
way that it actuates when the temperature reaches
(increasing or decreasing) the desired value (set point).
3.2 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).
3.3 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.
3.4 Prior to installation the instrument must be calibrated
and the definitive calibration values written on the
adhesive label using a suitable indelible ink pen.
3.5 If the instrument has been expressly ordered with
specific calibration, it is a good rule to check the
calibration values stated on the adhesive label, prior to
installation.
3.6 The position of the adjustment screws is given in fig. 1.
3.7 The effect that the direction of rotation of the
adjustment screws is described on the adhesive label.
NI-401E
Rev. 3 07/99
1 - Microswitch set point calibration screw
3 - Terminal block
4 - Electrical connection identification plate
Designation of the contacts:
C - Common
NA - Normally Open
NC - Normally Closed
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 initial temperature
range (when factory calibrated)
3
INSTRUCTION MANUAL
4 - SET POINT CALIBRATION
In order to proceed with the calibration and the periodical
functional verification of the instrument a suitable
calibration circuit (fig. 3) and an adequate heat source is
required.
4.1 PRELIMINARY OPERATIONS
4.1.1 Weatherproof temperature switches (Series
TWG) (Fig. 2)
Remove the blocking device fixed to the side of the
instrument case and the adjustment screw access plate.
Remove the cover be rotating it anticlockwise.
fig. 2 - Weatherproof tempeature switch cover blocking
device and plumbing
NI-401E
Rev. 3 07/99
Connection of C and NO terminals
• If the circuit is open at the working temperature, the
switch closes the circuit as the temperature increases
when the desired value is reached.
• If the circuit is closed at the working temperature, the
switch opens the circuit as the temperature decreases
when the desired value is reached.
Connection of C and NC terminals
• If the circuit is closed at the working temperature, the
switch opens the circuit as the temperature increases
when the desired value is reached.
• If the circuit is open at the working temperature, the
switch closes the circuit as the temperature decreases
when the desired value is reached.
4.2.3 The test instrument should have a measurement
range approximately equal to or slightly wider than the
temperature switch range and should have an accuracy
consistent with the precision required to calibrate the set
point.
4.2.4 The temperature switch must be mounted in the
normal installation position, i.e. with the stem or capillary
outlet downwards.
fig. 4 - Calibration circuit
a) Plumbing wire
b) Plumbing
c) Blocking nut
d) Blocking bracket
e) Adjustment screws access plate
4.1.2 Explosionproof temperature switches (Series
TAG) (Fig. 3)
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. 3 - Explosionproof temperature switch cover blocking
device
4.1.
4.2 CALIBRATION CIRCUIT AND OPERATIONS
4.2.1 Prepare the control circuit as indicated in Fig. 4.
4.2.2 The warning lamps should be connected to contact 1
or 2 in the NO or NC position according to the required
contact action.
TS - Temperature switch
TT - Test thermometer
TB - Thermostatic bath
4.2.5 Avoid forcing 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 in the contact codes) before proceeding with
the following operations (4.2.6-4.2.11) it is necessary to
proceed with the adjustment of the differential (see
attachment NI-705).
4.2.6 Increase the temperature in the circuit up to the
desired set point value for the first microswitch.
4.2.7 Use a wide bladed screwdriver, as indicated on the
adhesive label, until the relative lamp turns on (or turns
off).
- If the instrument is equipped with only one contact the
calibration is complete.
- If it is equipped with two contacts continue in the
following manner.
4.2.8 Vary the temperature until the desired set point value
for the second microswitch is reached.
4.2.9 Act on the adjustment screw of the second contact
as in point 4.2.7.
4.2.10 Repeat operations 4.2.6 and 4.2.7 on the first
contact, then operations 4.2.8 and 4.2.9 on the second
contact, until the required set point precision is obtained.
This is necessary due to the reciprocal influence which the
microswitches have with the sensitive element of the
instrument.
INSTRUCTION MANUAL
4.2.11 Check the calibration values (varying the
temperature in the circuit accordingly) and record them on
the adhesive label using a pen with indelible ink.
4.3 FINAL OPERATIONS
4.3.1 Disconnect the instrument from the calibration circuit.
4.3.2 Weatherproof temperature switches (Series
TWG)
Take the cover, ensure that the sealing gasket is correctly
fitted into its seat, insert the cover onto the case, with the
blocking gap positioned in correspondence to the blocking
bracket.
Turn the cover clockwise closing it tightly.
Mount the adjustment screws access plate, then the
blocking device as in figure 2.
4.3.3 Explosionproof temperature switches (Series
TAG)
Insert the closure plugs of the adjustment screw access
holes, block them using the internal device and if
necessary seal them with plumbing. Screw on the cover
and block it using the headless screw with which it is
equipped (Fig. 3).
4.3.4 Replace the supplied protection cap on the cable
conduit.
IMPORTANT: the protection cap should only be
definitively removed during the connection steps (see §5)
5 - MOUNTING AND CONNECTIONS
5.1 MOUNTING
Surface mount the instrument by means of the holes
provided, or pipe mount using the appropriate bracket
(see figures 6 and 7) in a vertical position (with the stem or
capillary outlet downwards). The chosen position must be
such that vibrations, accidental shocks or temperature
changes are within tolerable limits. The above also applies
to direct mounting.
5.2 BULB AND CAPILLARY
With reference to figure 5 unscrew the fitting (3) from the
seal press (2) and slide it off from the bulb (5). Mount the
fitting (3) on the thermowell and tighten it using the
appropriate key. Insert the bulb (5) into the thermowell (4)
after covering it with the paste to improve the transmission
of heat. Verify that the bulb touches the bottom. Insert the
PTFE seal with the relative stainless steel washers into the
fitting (3). Screw the seal press (2) onto the fitting (3)
taking care not to bend the capillary and relative sheath
and tighten until the PTFE seal is tight on the capillary
tube. Run the capillary protected by the armor in the
established direction, avoiding tight bends, and block
using the stainless steel bands. If a large amount of
capillary remains this should be rolled up and fixed tightly.
The coil must not have a diameter of less than 200 mm.
5.3 ELECTRICAL CONNECTIONS
5.3.1 Set up the cable protection tube according to the
applicable standards (especially for explosion-proof
prescriptions). In many applications this is associated to
the process piping and is subject to condensation. For this
reason it is necessary to provide means to prevent
condensation from entering the instrument case. The
arrangement shown in figure 6 or 7 is therefore
recommended.
5.3.2 Check that there is no power in the lines.
5.3.3 Remove the cover and carry out the cabling and
connections to the terminal block (see fig. 1).
Flexible cables with a maximum section of 1.2 mm
(16AWG) are recommended using pre-insulated fork
thimbles. Do not touch the adjustment screws and do
2
NI-401E
Rev. 3 07/99
not bend the elastic microswitch supports in order to
prevent the instrument calibration being altered.
5.3.4 Ensure that no deposits or wire ends remain inside
the case.
5.3.5 Once the connection operations have been
completed, replace the cover and ensure that it is properly
sealed and blocked. See Fig. 2 and 3.
6 - INSTRUMENT PLUMBING
6.1 Weatherproof temperatures switches (Series
TWG)
The plumbing, aimed as a guarantee against possible
tampering of the calibration and electrical connections, can
be carried out using a flexible steel wire (a) inserted into
the holes in the locking nut (c) and the bracket (d)
provided for this purpose (see figure 2).
6.2 Explosionproof temperature switches (Series
TAG)
Plumbing is not necessary as the cover is blocked with a
headless screw, the closure plugs of the adjustment screw
access holes are blocked by means of the internal
blocking device and the instrument does not have to be
opened when installed.
fig. 5 - Mounting the bulb
1) Armored capillary
2) Stuffing nut (SW 12)
3) Rotating fitting (SW 22)
4) Thermowell
7 - PUTTING INTO OPERATION
As the signal transmitted by the instrument is used in a
complex system, it is necessary that the means of putting
it into operation are established by those in charge of the
plant. The instrument starts working as soon as it is
connected to an electrical line.
8 - FUNCTIONAL VERIFICATION
This will be carried out according to the Client’s control
procedures. Series TWG instruments can be verified.
Series TAG instruments can only be verified on the plant if
test equipment suitable for the environment is available
and if there is no current in the electric line.
If this is not the case it is necessary to stop operation,
dismount by means of the three piece joints and carry out
the verification in a test room. Verification consists in
checking the calibration value and possibly regulatory
the adjustment bush (see §4).
5) Bulb
6) Stainless steel washer
7) PTFE washer
INSTRUCTION MANUAL
9 - TROUBLESHOOTING
IMPORTANT NOTE: operations involving replacement of essential components must be carried out at our
workshop, especially for instruments with explosionproof certificate; this is to guarantee the user the total and
correct restoration of the product’s original characteristics.
MALFUNCTION PROBABLE CAUSE REMEDY
Wear of contact surfaces between
microswitch pin and sensing element tip.
Wear of contact surfaces between
microswitch cradle and adjustment
screw.
Possible encrustations or corrosions on
Set point shift
Poor Repeatability
Slow Response
Failed or Undue Actuation
Undue Actuation
10 - STOPPING AND DISMOUNTING
Before proceeding with these operations ensure that the
plant or machines have been put into the conditions
foreseen to allow these operations.
10.1 Remove the power supply (signal) from the electrical
line.
With reference to figure 5.
10.2 Loosen and remove the stuffing nat (2) being careful
not to bend the capillary and protective sheath (1).
10.3 Loosen and remove the fitting (3) then extract the bulb
(5) from the thermowell (4) holding it by the capillary tube
(1), without bending it.
Do not waste in to environment the process fluid if
polluting or harmful to people.
With reference to figures 6 and 7.
above listed surfaces.
Permanent deformation of the sensitive
element due to fatigue or non-tolerated
over-ranges.
Loss of filling fluid.
Assembling screws loosened.
Encrustations on bulb or thermowell Check and clean encrustated surfaces
Microswitch contacts damaged
Electrical joints loosened
Electrical line interrupted, or short circuit
Accidental impacts or excessive
mechanical vibrations
10.4 Unscrew the three piece joint (8) (electrical cable
tubing).
10.5 Remove the instrument cover and disconnect the
electrical cables from the terminal block and earth screws.
10.6 Remove the screws fixing the case to the panel (or
pipe) and remove the instrument, taking care to slide the
electrical conductors out from the case.
Replace the instrument cover. Insulate and protect the
conductors remaining on the plant. Temporarily plug the
thermowell.
11 - DEMOLITION
The instruments are mainly made of stainless steel and
aluminium and therefore, once the electrical parts have
been dismounted and the parts coming into contact with
fluids which could be harmful to people or the environment
have been properly dealt with, can be scrapped.
Recalibrate
Recalibrate
Clean surfaces and recalibrate. Check
housing tightness.
Recalibrate or replace the sensitive
element with another made of a suitable
material. If necessary apply a fluid
separator.
Replace sensing element with another
one of same type
Check terminal screws, microswitch,
electrical subassembly, fastening screws
Replace microswitch
Check all electrical joints
Check state of electrical line
Modify installation arrangement
NI-401E
Rev. 3 07/99
INSTRUCTION MANUAL
NI-401E
Rev. 3 07/99
WEATHERPROOF EXPLOSIONPROOF
fig. 6 - Example of connections - fig. 7 - Example of connections -
1) Weatherproof temperature switch
series TWG
2) Capillary spacer
3) Thermowell
4) Bulb
5) Process piping
6) Derivation
7) Flexible armour
8) Cable gland
9) Bracket for 2” pipe
10) 2” pipe
fig. 8 - Thermometric wells: example of installation
Minimum dimensions 3"; for lesser dimensions provide for an increase in diameter up to 3".
Minimum dimensions 6"; for lesser dimensions provide for an increase in diameter up to 6".
1) Explosionproof temperature switch
series TAG
2) Capillary spacer
3) Thermowell
4) Bulb
5) Process piping
6) Derivation
7) Blocking joint
8) Cable gland
9) Bracket for 2” pipe
10) 2” pipe
ETTORE CELLA SPA Viale de Gasperi, 48 - Casella Postale (P.O. Box) 96 - I 20010 Bareggio (MILANO) ITALY
Telefoni +39 029036.1146/1237/1241 – FAX +39 029036.1331
e-mail: cella@ecellaspa.com
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