118_4416655_Rev06

Appendix
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Appendix C Average product temperature verification procedure
The average temperature measurement from VITO temperature probes, MRT’s and MPT’s can be verified by
means of a manual temperature measurement with a calibrated portable electronic thermometer. The calibration
certificate shall be available and lists the eventually temperature deviation from the instrument.
Warning
In hazardous areas it is compulsory to use personal protection and safety gear such as:
hard hat, fire-resistive overall, safety shoes, safety glasses and working gloves.
Avoid possible generation of static electricity.
Use non-sparking tools and explosion-proof testers.
Make sure no dangerous quantities of combustible gas mixtures are present in the working area.
Never start working before the work permit has been signed by all parties.
Pay attention to the kind of product in the tank. If any danger for health,
wear a gas mask and take all necessary precautions.
When situated at an open gauge hatch, always stay upwind (vapours blowing away from you).
Before lowering the portable temperature probe into the tank,
make sure the portable electronic thermometer is properly grounded to the tank.
1) Read the product level from the level gauge or by manual dip. Round off this value to the nearest 0.5 m
(1 ft). For a proper verification, the product level shall be at least 4 m (13 ft).
2) The manual temperature will be taken at 5 points. Calculate the interval as follows:
Interval = (product level [m] – 2 m) / (5 – 1)
or (product level [ft] – 6 ft) / (5 – 1)
3) Locate a gauge hatch, closest to the average temperature element and open it. Slowly lower the probe
from the portable electronic thermometer till 1 m (3 ft) above the bottom.
4) Wait till the temperature reading on the portable electronic thermometer is stabilized. Note the
temperature reading from the portable electronic thermometer, corrected for eventually deviations
according to the calibration certificate.
5) Pull up the probe for the Interval value and repeat step 4.
Note:
Make sure that with the last (5 th ) measurement, the probe of the portable electronic thermometer
is at least 1m (3 ft) below the liquid surface.
6) When all 5 measurements are completed, average the 5 manual temperature values and compare it with
the average product temperature reading from the gauge. The difference in temperature shall be less than
0.5 °C (1.0 °F).
Note:
In the case the 5 manual temperature reading differs more than 1 °C (2 °F) from each other, it is likely the
temperature in the storage tank is not homogeneous. In that case 10 measurements shall be taken
(Interval to be calculated by dividing by (10 – 1)).
For product levels below 4 m (13 ft) the number of measurements is according to table C-1:
Product level
Measurement location
3 – 4 m (10 – 13 ft) 1 m (3ft) above tank bottom, half way liquid level, 1 m (3 ft) below liquid surface
1.5 – 3 m (5 – 10 ft) Half way liquid level