1. ## Vacuum Drying times

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Hi all, i am doing some researce on vacuum drying. Does anybody know of how to relate a vacuum drying time to an area of steel? for example, if i have 850 square meters of steel (a subsea caisson and risers) how long would it take to dry the surfaces at a negative pressure of 0.7 bar? (approx). Very new to this subject so any info would be greatly appreciated.

2. Well, for a start, stop using conflicting terms. "negative" and "Pressure" are total opposites. It is Vacuum or it is Pressure.

As to the rest, I will give you your answer if you tell me how long this piece of string is.

Meaning you have not provided any useful information. There are so many variables it is impossible to advise from what you have supplied. Humidity, air temperature, metal temperature, Dew Point, flow rate to name just a few. Are you bagging this or just waving a hose end around? Do you have a spreader or concentrator nozzle?

Dave
Generally, I will not give you the answer to your question, but I *will* guide you into discovering how to solve this yourself.
Insanity: "doing the same thing over and over again and expecting different results." Albert Einstein

3. ## Moisture Removal on Aluminum Cylinders

Greetings,

I am working in a process of drying and evacuating moisture and residual gases from aluminum cylinders. Currently the cylinders are subject to a temperature of 155 F and a vacuum of 0.200 Torr. The cylinders are 0.16L aluminum cylinders. The environmental conditions when the valve is installed in the cylinder are 60% RH and 70 F so I assume those values as the initial values inside the cylinders.
My first question is: how to calculate the time I need to subject the cylinders to 0.200 Torr and 155 F to assume that the inside of the cylinder is dry? (I know perfect dryness is impossible but I am looking of a theoretical value).
My second question is: is there a way to measure %RH under those vacuum conditions to end the process base on %RH?
Thank You

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