Calculations Tankvision
52 Endress+Hauser
8.5 CTSh
8.5.1 What is CTSh
CTSh stands for "Correction for Temperature of the Tank Shell". CTSh is about correcting for
when the temperature of the tank shell is different than the calibration temperature of the
tank.
This temperature influence affects the calculated Inventory via (1) the gauge reading, and
(2) via a change in the capacity of the tank as the tank diameter has changed under the
temperature effect.
Temperature effect on gauge reading
The temperature effect via the Gauge Reference Height (GRH) affect the level reading and
depends on:
• The actual product level in relation to the Gauge Reference Height (GRH),
• The gauge type, for example radar and servo are differently affected,
• The thermal expansion coeficient of the tank steel,
• and the actual tank shell temperature in relation to the tanks shell calibration
temperature.
The temperature correction for the Gauge Level reading should be corrected in the Level
gauge and NOT corrected in the Tank Inventorey System.
Reason is that it makes more sense to this correction in the gauge itself:
• Level reading in Gauge ans System should be identical with the same correction applied.
• The required correction depends on the gauge type. A servo, needs for example a different
correction as the temperature effects on the measuring wire in the tank partly
compensates the temperature effects of the tank shell. For a Radar this is not the case.
• Why burden the Tank Iventory system with correction which are gauge specific.
Temperature effect on tank capacity
L00-NXA82xxx-15-00-00-xx-001
The temperature effects also the tank capacity via the tank shell diameter. With the changed
diameter, the surface area is changed, and as result the tank can contain more or less liquid
product depending on wheter the tank shell temperature is higher or respectively lower than
the tank shell calibration temperature.
Temperature difference Volume change Temperature difference Volume change
1.0 °C (34 °F) 0.002% 50.0 °C (122 °F) 0.110%
5.0 °C (41 °F) 0.011% 60.0 °C (140 °F) 0.132%
10.0 °C (50 °F) 0.022% 70.0 °C (158 °F) 0.154%
20.0 °C (68 °F) 0.044% 80.0 °C (176 °F) 0.176%
30.0 °C (86 °F) 0.066% 90.0 °C (194 °F) 0.198%
40.0 °C (104 °F) 0.088% 100.0 °C (212 °F) 0.220%
Temperature Effect on Tank Volume for a given height of liquid (based tec for steel: 22x10
6
/°C
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