Heat loss from tank roof

If well insulated, (and I know it's not), then temperature of the gas should be the same as the liquid once an equilibrium has been reached. Since it's not well insulated, your heat loss will depend on the driving forces (delta T's), which will change with the atmospheric conditions. If you assume a constant atmospheric temperature and humidity, take into account the heat transfer of the cover (i.e. material specific), you might be able to backsolve for the theoretical heat loss... Vapor pressure would tell you how much oil you have in the gas phase at a certain temperature. So I suppose if you can get a sample of gas and analyze the amount of oil in that phase, you could backsolve for temperature, theoretically. However, theory only goes as far as paper. For the real world, I suggest you just get out there and measure it for a true value.

Thanks for the ideas.

Is heat conduction from the warm wall plates to the roof possible ? An affirmative answer would somehow affect heat losses from the roof by convection and radiation.

Sounds reasonble. I will see what I can find. Thanks for the thought. HAZOP at

You could reduce heat loss by installing a floating roof. If interested, try sales@allentech.com

1) To tell if oil vaporization is a significant factor: check for condensation on the underside of the roof. If this is the case, then factor in the cooled droplets falling back into the tank, i.e., you have a heat pipe. Find an area where dripping is uniform, then put out a large container for 24 hrs to determine the flux.

I actually think this is unlikely, you must have some thick stuff to keep it at 175 F.

2) aspearini1 is right, you need to measure some temperatures. I suggest you get several data loggers & track the inside roof T, outside roof T and ambient T.
On your way up the ladder, check some outside wall T’s, too. There may be a T gradient re 25362’s idea.
Probably, watch the Weather Channel & write down the wind speed hourly.
And, of course, any precipitation.