Regarding the amount of nitrogen used for nitrogen sealing in storage tanks
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I need help. I’m currently constructing 6 internal floating roof storage tanks with a capacity of 1W each, and the client requires nitrogen sealing. How should I determine the amount of nitrogen needed? I remember that when working with small tanks, we used the amount of material entering and leaving as a reference, but later we realized there was a problem: the heat exchange in large tanks was quite severe. The standard value for cold air intake per 1 cubic meter of tank volume is 1210 standard cubic meters; so should we consider 9000 standard cubic meters of nitrogen for those 6 tanks?
Does the internal floating roof also come with a nitrogen seal? Has the floating disc supplier been confirmed?
Our company also has storage tanks with internal floating roofs and nitrogen seals, but all of them are 1000 m³ in size. Wanli’s recommendation is to add connecting lines for identical or similar types of equipment; the design basis can be found in the design manual: 22 installation locations for pipelines in the tank area, which helps to significantly reduce nitrogen consumption as well as oil and gas losses. It is also necessary to consult the design institute to add safety measures!
Theoretically, it is generally not recommended to use a design with an internal floating roof and a nitrogen seal, as this requires high stability from the floating disk and also makes load calculations more complex. If excessive breathing loss is a concern, it is recommended to use an internal floating roof directly. As for nitrogen sealing, it is generally done for safety reasons; if the medium is toxic or similar, it is employed to reduce leaks
Internal floating roof tanks are rarely equipped with a nitrogen seal, unless they store Class A or toxic substances; in such cases, nitrogen is used to dilute the gaseous portion of the substances that are released. Since the inner floating roof tank is equipped with ventilation windows all around it, and nitrogen has a lower density than air of the same volume, it can be said that what occurs is more of a dilution rather than a complete sealing.
Firstly, the material output volume must be taken into consideration; the nitrogen inlet volume should correspond to the output volume； As for the mentioned thermal breathing, if the tank is insulated, then its impact is minimal and can be ignored. If it is a bare tank, then it must be considered in accordance with the specifications.
Yes, I hadn’t encountered internal floating roofs with nitrogen sealing before, but this project happened to have that feature. Initially, it was internal floating roof storage tanks; later, as food-grade requirements were imposed on the products, the issue of corrosion protection for the inner walls had to be taken into consideration. No anti-corrosion paint that meets food-grade standards and at the same time has good electrical conductivity was found; therefore, considering changing the internal floating roof to an arch-shaped roof with nitrogen sealing was an option. Since the fire separation distance was insufficient, switching to an arch-shaped roof was also considered, but in the end the internal floating roof was retained. Moreover, supervision here is strict; one doesn’t dare to remove the floating disk on their own, which results in the use of a nitrogen seal with an internal floating roof.:D Does the design team have any good solutions? Please share them.
There’s nothing special about that other thing; what’s crucial is this floating pad. If the original floating pad is used, there will likely be difficulties. If replacing the floating disc is necessary, there may not be many options available.