Must gasoline storage tanks be floating roof tanks equipped with a nitrogen blanket?

Floating roof tanks are necessary. As for whether nitrogen sealing is used or not, I can’t answer; I’m also learning about it*

Personal opinion: An internal floating roof is definitely necessary. Without it, 1) there will be excessive volatilization losses, and 2) the oil and gas concentration at the top of the tank will be too high, which is also unsafe. When using nitrogen sealing, factors such as the amount of nitrogen used, pressure maintenance, concentration, replenishment, and protection against water vapor all need to be taken into consideration. There don’t seem to be any strict requirements in the relevant design specifications either. Of course, if conditions permit, using nitrogen sealing is definitely advantageous over internal floating roofs in terms of preventing losses. The floating-roof gasoline tanks in the tank farm where I work are equipped with nitrogen sealing systems, but unfortunately they have never been used and remain idle. The expert downstairs, please provide a detailed answer for the poster.

The specifications require an internal floating roof; theoretically, no additional nitrogen seal is needed.

3rd floor: How is your nitrogen sealing designed? What is the structure like? I’m sharing this; I really need this kind of information right now as I’m studying*.

Nitrogen sealing involves selecting the diameter of the nitrogen sealing pipeline based on the amount of material fed into the storage tank and the pressure in the nitrogen system (there are specific requirements regarding the nitrogen supply rate; I can’t remember exactly how many meters per second it should be). A self-acting control valve is installed on the nitrogen pipeline (it is necessary to create a pressure tapping hole on the tank), and manual valves are placed before and after the control valve. Once the opening pressure of the control valve is set, everything is ready. In this way, when the pressure inside the tank falls below the set value, the control valve opens to supply nitrogen, and it closes once the desired pressure is reached. Excess pressure in the tank is released through the breather valve. If a particular oil product is stored in multiple tanks, it is best to connect the gases from these tanks using vapor equilibrium lines.

May I ask, if a pressure tapping hole is to be created on the tank, should the nitrogen inlet be placed at a distance? Is it possible to avoid creating such a hole and instead use a self-acting control valve? Also, you mentioned that there are multiple oil tanks; by connecting their vapor lines together, could a nitrogen seal be established in that case? Thank you

It is better to place the pressure measurement point on the tank top at a location far from the nitrogen inlet. If a stand-alone control valve is installed on the tank top, it is also possible to add a tee for taking pressure readings if there were previously a pressure transmission point on the tank top; however, pressure readings are necessary as the stand-alone control valve needs to have access to the pressure inside the tank in order to function properly. If the diameter of the gas-phase equilibrium line is large enough to achieve an ideal balancing effect, an adjustable valve can also be used; such a valve can be installed on the ground to adjust the pressure via the equilibrium line (this is how spherical tanks are designed in our facility), with the pressure sampling point located at an opening on the equilibrium line.