Installation and Operating Instructions
With regard to all installation/attachment options mentioned on the Installations page,
Reckmann GmbH recommends to ensure that the connections with
the process are tight, firm and securely in accordance with the recognized rules
of technology and the regulations applicable at a given
time.
Furthermore, you should take note of the following information:
- The lifetime of thermocouples can be extended in many
operating circumstances by fitting an additional ceramic inner tube to the
thermocouple assembly.
- To avoid deflection in the case of longer metal protection tubes
(particularly at temperatures above 500 °C), the latter should preferably be
fitted vertically; if the fitting position is horizontal, corresponding
supports should be provided.
- Ceramic protection tubes must not be subjected to a mechanical load (e.g.
bending or impact effect) or to a rapid change in temperature (temperature
shock). To avoid cracks, ceramic protection tubes that, for example, need to
be inserted into a hot furnace should only be inserted very slowly or in
pre-heated mode, avoiding direct contact with the flames. According to DIN 43
724, no visible damage should occur to the ceramic protection tubes if,
depending on the outer diameter, they are inserted into a furnace that has
been heated to the permissible constant temperature of the protection tube
(depending on the material, 1,500°C or 1,600°C) with the following insertion
speeds: if D = 10 mm, 100 cm / min; if D = 15 mm, 50 cm / min and if D = 24
and 26 mm, 1 cm / min. Reckmann GmbH recommends (particularly with D = 10 and
15 mm) that the protection tube be inserted much more slowly into the hot
process and also removed again in the same way. In addition, if operating
temperatures are above 1200°C, ceramic protection tubes should only be fitted
vertically.
- Standard aluminium/plastic connection heads are equipped with rubber seals
and suitable for ambient temperatures up to 80°C. Aluminium heads can, on
request, also be supplied with silicon seals, which can be used at up to
around 130°C. The permissible ambient temperature is reduced to around 80°C if
a measurement transducer / transmitter is fitted on the connection head.
- To keep measurement error caused by heat dissipation (e.g. via the
protection tube or the sheath tube) negligibly small, the tip of the
temperature sensors should be immersed as deeply as possible into the medium
to be measured. For thermocouple assemblies and standardized resistance
thermometers, the immersion depth in fluids should be at least 6 times the
diameter of the protection tube, while with air and gas it should be at least
ten times that. In the case of sheathed thermocouple assemblies and sheathed
resistance thermometers, the minimum fluid immersion depth is 5 times the
sheath tube diameter or 20 times the sheath tube diameter in air/gas, with the
immersion depths having to be increased for sheathed resistance thermometers
by the temperature–sensitive lengths each time (usually around 35 to 40mm). If
tube cables with small diameters do not allow sufficient immersion depth in
vertical installation, the temperature sensors should be fitted diagonally or
in a tube elbow against the direction of flow.
- The connection between the (sheathed) thermocouple assembly and the
measuring equipment or the external reference junction may only be established
using a compensating or extension cable matching the thermocouple (see the
page about compensating and extension cables). You must ensure that the cables
are connected in the correct polarity.
- Resistance thermometers allow standard copper cables to be used to connect
to the measuring equipment. The number of wires depends on the configuration
of the resistance detector (single or dual) and the circuit technology. Where
possible, copper cables having a cross-section of 1.5mm2 should be used.
- When fitting sheathed resistance thermometers and similar configurations,
you must ensure that there is no bend in the sheathed cable at a range of
around 50mm behind the rigid metal tube welded to the sheathed cable (see
Figure 6, parts i and k on the "Configuration of Resistance Thermometers"
page. It is advisable, however, to enlarge this unbent area, if
possible.
You can bend the remaining sheathed cable without
impairing the technical properties (this also applies to sheathed
thermocouple elements), as long as the bend radius is
greater than 5 times the outer diameter of the sheathed
cable.
|
