Calculated
Vapour Savings
A.P.I. Publication
2517 (Evaporation Loss from External Floating Roof Tanks, second
edition, Feb. 1980) provides a sample calculation for a 100 foot
diameter floating roof tank, containing gasoline of 10 psi RVP and
fitted with a mechanical shoe primary seal. The calculated total
loss from the seal area was 132 bbl / year.
Using similar
criteria and applying the site characteristics provided for a particular
U.K. terminal:-
Tank diameter
= 120 feet
Average windspeed = 12 mph
Vapour pressure = 6 psia
Metal shoe primary seal
Calc. evaporation
loss = 233 barrels / year
The same tank
fitted with an M.N.P. secondary seal would result in losses of about
11 barrels / year.
Savings
= 222 barrels / year
If the primary
seal fitted is a vapour mounted foam seal then the loss is about
1,703 barrels / year.
An M.N.P. secondary seal would reduce this to about 598 barrels
/ year.
Savings
= 1,105 barrels / year.
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