rnln wrote:Q1: If I lift the fuel tank, can I easily put fuel tank back in place without damaging the foam surround?
I doubt the foam would remain intact. You probably will have to saw the foam away from the tank on the sides of the tank. The foam on the bottom of the tank will probably have to be broken away when you lift out the fuel tank. Usually when a tank is removed, the foam is removed and not replaced when the tank (or a new tank) is installed.
rnln wrote:Q2: I plan to pressure test the fuel tank: how many PSI should I test with?
Use very low pressure, probably only 3-PSI at most. Consider the total force exerted on the interior surface of the tank. Calculate that area and multiply by the PSI to find the total force.
For example: a 77-gallon fuel tank can be filled with 77-gallons of gasoline. Gasoline has a volumetric density of 231-cubic-inches per gallon. Thus the volume of the tank must be at least 17,787-cubic-inches.
Since no information is given about the surface area of the fuel tank, the surface area will be deduced from the volume of the tank. For this purpose the fuel tank shape is assumed to be a cube (to simplify calculations), and thus each side of cube would have a length of 17787^0.33 = 26.1-inches, and a surface area of 26.1^2 = 681-square inches. There are six sides to a cube so the total surface area is then 6 × 681 = 4,087-square-inches. Applying a uniform pressure of 3-lbs-per-square-inch will then exert a total force on the the tank of 4,087-square-inches × 3-lbs-per-square-inch = 12,262-lbs.
Other complex fuel tanks shapes may have a different ratio of volume-to-air; calculation of surface area can be done if the shapes and surface areas of each facet of the tank shape are known.
In some instances, the OEM label on the fuel tank will give advice on the maximum pressure to be used in testing. If the OEM label is no longer legible, contact the OEM manufacturer (FMT) for advice. At one other source of advice on the web cautions against using
no more than 3-PSI.