KROHNE OPTITEMP TCA Ex EN - Manual (Page 22)

3
INSTALLATION
22
OPTITEMP TRA/TCA
www.krohne.com 10/2010 - 4001087001 - Ex AD OPTITEMP TRA/TCA R02 en
Once you have calculated the specified parameters and device properties, you must determine
the maximum permitted temperatures for your specific measuring point in three steps. Use the
tables in the previous subchapters to do this:
• Determine the maximum permitted product temperature ( refer to Maximum permitted
product temperature on page 12).
• Determine the maximum permitted temperature at the process connection ( refer to
Temperature at process connection (without temperature transmitter) on page 13, refer to
Temperature at process connection (with temperature transmitter) on page 15 or refer to
Temperature at process connection (with temperature transmitter, classes T5 and T6) on
page 17).
• Find out whether the thermometer requires a heat-resistant connecting cable; if so ensure
that the connecting cable can withstand the process conditions ( refer to Temperature at
process connection for thermometers with connecting cable on page 18).
Example: Determining the maximum permitted temperatures
This example is based on a TxA-F13 thermometer with head-mounted transmitter. It has the
following features and is subjected to the following process conditions:
• Length of neck pipe: min. 80 mm / 3.15"
• Maximum ambient temperature of transmitter: 85°C / 185°F
• Sensor output: P
o
= 500 mW
• Ambient temperature at measuring point: T
a
= 40°C / 104°F
• Product temperature: T
M
= 70°C / 158°F
• Temperature at process connection: T
P
= 50°C / 122°F
Step 1: Calculate the maximum product temperature
• Refer to the table with the maximum permitted product temperatures ( refer to Maximum
permitted product temperature on page 12).
• Look along the header of the table until you come to the column with your sensor output P
o
(in
this case: 500 mW).
• Look down this column and find the product temperature at your measuring point (in this case:
70°C / 158°F).
• If you can't find this figure, always look at the next figure up.
i The maximum permitted product temperature is 92°C / 198°F and the temperature class is
T4.
.book Page 22 Friday, November 19, 2010 2:23 PM