- 6 -
Flexible Sheath Resistance and Thermocouple Temperature Sensors FlexiTEMP
®
60
4. Installation, operation and maintenance
4.1 Installation and commissioning
4.1.1 General
Low depth of sensor immersion to measured medium can
cause a measurement deviation because the heat is diverted
through a sensor stem, protective tube or thermowell. To
prevent this fault the recommended depth of immersion is 8
to 10 times diameter of thermowell measuring end for liquids
and 10 to 15 times diameter of thermowell measuring end for
gases.
Sensors may be installed in any position. In version with head
MA (code H1 resp. H1G..) with cable outlets facing down or to
the side if possible.
Vertical position with head up or cable outlet up is considered
as a standard position.
Sensor with head (code H1) is in case of necessity fixed on
wall by holder (D3). Sensor with head (code H1G..) is fixed by
screwing into the thread of welded on piece or into the bore on
the pipe wall, technological equipment, etc.
Cable sensors (code VV, KV, KS, KM) are fixed to the technology
by fixing shift pipe union as standard. Using without fixing shift
pipe union is not excluded in some applications.
Resistance sensors are connected to the decoding devices
using copper connection cable wires with cross section 0.5
to 1.5 mm
2
. When the sensor is used in the environment with
higher level of interference, it is recommended to connect the
shield wire according to usual engineering practice. The stem is
not electrically connected to the shield.
Thermocouple sensors are connected to the decoding devices
using extension or compensation cable wires with cross section
0.22 to 1.5 mm
2
.
Connection terminal of sensors with head is accessible
after removal of the head cover. Drawing of the connection
terminals and wiring of cable sensors, sensors with connector,
and sensors with head are shown on the scheme of electrical
connection. The sensor outlet shall be carefully sealed after
connection of the wires.
4.1.2 Commissioning
Resistance temperature sensor without head (with flying leads,
with connected connection wires) is ready for operation after
connection of flying leads or copper connection wires to the
terminals of the associated apparatus and after switching on
the power supply.
Resistance temperature sensor with head is ready for operation
after connection of copper connection wires between the
sensor terminals and terminals of the associated apparatus
(transmitter, digital display etc.), mounting head cover and after
switching on the power supply.
Thermocouple temperature sensor without head (with flying
leads, with connected compensation wires, with connector)
is ready for operation after connection of flying leads of
thermocouple or compensation (extension) wires to the
terminals of the associated apparatus (transmitter, thermostat
of comparator connections, devices with inner compensation
etc.) or after connection of sensor with connector to the other
part of the connector with connected compensation wires
connected to the associated apparatus
Thermocouple temperature sensor with head is ready for
operation after connection of compensation (extension) wires
between the sensor terminals and terminals of the associated
apparatus (transmitter, thermostat of comparator connections,
devices with inner compensation etc.) and after mounting head
cover.
Before commissioning, check whether the measuring circuit
break has not occurred and if the insulation resistance has not
been lowered.
4.1.3 Special conditions for safe use of sensors
in Intrinsically safe version (code EI)
1. Temperature sensors in intrinsically safe version (code EI)
can be connected to intrinsically safe circuits of electrical
equipment Group II . Degree of protection and placement of
specific versions in specific areas of explosive atmospheres are
described in section 3.3. Temperature sensor without transmitter
does not have any own ignition source. All potential sources of
ignition are brought form environment (electric energy causing
warming and thermal energy from a technological connection)
and their size and safety (danger) must be assessed by the
user during installation. Input parameters of the sensor without
the transmitter are U
i
= 30 V, I
i
= 30 mA , P
i
= 0,1 W. Sensor with
length 1 m has a maximum internal parameters C
i
= 1 nF and
L
i
= 0,020 mH. In case of longer sensor, these values should be
multiplied by the length of the sensor. Input parameters of the
sensor with transmitter/display installed in the sensor head are
given by parameters of used transmitter/display.
2. When connecting the sensor into the intrinsically safe circuit,
these circuits must be considered to be electrically connected to
earth potential through the grounded sheath of the sensor. The
user must eliminate other connection of intrinsically safe circuit
to earth potential using associated apparatus (transmitter, Ex
barriers) galvanic isolated from the other circuits. Associated
apparatus shall meet the requirements of EN 60079-11. During
installation is also necessary to respect the requirements of
EN 60079-14, EN 60079-25 and other relevant standards.
3. Sensors do not have ground terminals. Their connection with
the ground potential is necessary to ensure by other means in
accordance with the relevant standards (for example by access
to the technology).
4. Measurement part of the sensor has surface temperature
equal to the temperature of the process fluid and therefore it is
crucial for determining the temperature class (for T6 to T1) or
the maximum surface temperature Tx.
5. The surface temperature of sensor head depends on the
sensor type, method of installation, process temperature,
ambient temperature and power loss of used transmitter.
Temperature class of temperature sensor head with mounted
transmitter/display with max power P
imax
= 1 W is T4 according
to EN 60079-0 with ambient temperature up to 80 °C. Used
transmitter/display and associated apparatus must have a
type certificate in accordance with the relevant standards and
regulations. Final intrinsically safe circuit has to be assessed
according to EN 60079-25. If further warming of head due
to heat transfer of technology can occur, it is necessary to
determine the temperature class based on information from
manual or based on measuring surface temperature according
to relevant standards.
6. Temperature of other sensor surfaces that are in contact
with explosive atmosphere must be determined individually
after on-site installation and must not exceed the ignition
temperature of the explosive gas atmosphere and/or exceed
2/3 of Tcl - ignition temperature of scattered dust.
7. If the measuring end of sensor in version EI is installed
in zone 0 or 1, and if electric power P
0
of intrinsically safe
transmitter passed into the sensor is higher than 0.05 W, the
increase of temperature of the measuring end in the case
of failure of the transmitter can exceed 10 °C. In this case,
it is necessary to determine real increase of temperature of
measuring end under these conditions and to assess the
ignition risk of explosion. When installed in Zone 2, transmitter
