Floating Roof Critical Zone Calculation

[sdominique]

Hello Everyone,

Does anybody knows how to calculate a floating roof critical zone please?
It's a Mogas tank and I have the weight, the range of density and temperature.
Thank you very much

 

[LittleInch]

Floating Roof
When afloat, floating roofs displace a volume of liquid equal in weight to the weight of the roof, therefore
an accurate assessment of the total weight of the roof is very important. The physical measurement of the
roof should be made detailing each piece of metal used in the construction, together with its exact
position in the roof. Using these measurements, calculations are made which give both volume and
weight. Floating roofs are also fitted with drain lines, seal tensioners, support legs and roof ladder, which
must also be measured and taken into account when calculating the roof weight.
All measurements and calculations should be checked against the maker's design specifications and
construction drawings.
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One very important measurement is the height of the lowest part of the roof above the datum plate. This
height determines the lower position of what is known as the "Critical Zone", the higher position being
determined by calculation. In large floating roof tanks the roof legs can be set in a high or low position
which gives rise to two "Critical Zones". This critical zone is the part of the tank where the roof is not fully
supported by its legs or afloat. Measurements of oil quantities with the roof in this position are virtually
impossible to make accurately unless the critical zone has been liquid calibrated.

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[sdominique]

Thank you LittleInch, what i'm trying to do is to calculate the highest position of the floating roof but I don't know how to do it.
Thanks for your reply though.

 

[LittleInch]

I'm not following you.

The highest position in the critical zone is just when the legs lift off the floor.

This is set / identified on the tank data sheet. as is the maximum height of the roof within the tank.

Often you get two heights - a normal operation one and a maintenance one where the height is higher so that it's not like a coalmine when you need to enter the tank for cleaning or maintenance. one is probably 0.9m and the second 1.8.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.