Installation – KROHNE OPTITEMP TRA-TCA EN User Manual
Page 27
INSTALLATION
3
27
OPTITEMP TRA/TCA
www.krohne.com
08/2010 - 4000630501 - MA OPTITEMP TRA/TCA R01 en
A thermowell surrounded by the measured medium is a body behind which vortices periodically
are released ("Kármán vortex street"). If the frequency of the vortex detachment is equal to the
resonance frequency of the thermowell, it starts to vibrate. If this happens for a short period of
time, such as when starting up the system and the frequency of the vortex detachment passes
through the resonance range of the thermowell, no damage is caused. The opposite is true,
however, if the vibrations remain permanently in the resonance range.
3.5.3 Temperature load
The temperature of the measured medium and the thermal dissipation via thermowell and neck
tube also cause the connection head to heat up. After some time, the interior of the connection
head and any existing head-mounted transmitter heat up to the temperature of the housing.
This occurs in thermometers with and without neck tubes. A neck tube, however, causes thermal
decoupling and can prevent the connection head or temperature transmitter from overheating at
high process temperatures.
CAUTION!
When the temperature is too high, the connection head and the components found in it
(e. g. temperature transmitter or display) can be damaged or destroyed! It is your responsibility
as the operator to ensure that the connection head does not get too hot. If this does happen,
select another installation site or a thermometer with a neck tube or, with insertion-type
thermometers, increase the distance between the connection head and the process connection.
CAUTION!
Sometimes even a neck tube cannot prevent the maximum permissible temperature in the
connection head from being exceeded! The connection head on thermometers without a neck
tube heats up faster than thermometers with neck tubes but you still must always take into
consideration the installation situation as well as the ambient and process temperatures!
.book Page 27 Tuesday, August 17, 2010 12:18 PM