Need help with nitrogen sealing calculations! !
Thread Content
For a recent project related to the storage and transportation of alcohol, 4 storage tanks with a capacity of 650 m3 each were installed, 1 tank with a capacity of 2100 m3, and 1 tank with a capacity of 2900 m3. During the fire safety inspection, the fire department requested nitrogen protection to be implemented. I performed calculations based on both HG/T 20570 and API 2000, and the results obtained were quite high; the calculations are shown in the figure. Since the storage tank has no insulation and is located in areas with a latitude of less than 40, it’s unclear whether this is due to calculation errors or misunderstandings – the amount of nitrogen required for sealing is much higher than expected. My initial idea was that the breathing volume of a storage tank is equal to the pump inflow and outflow rates, plus the volume changes in the liquid/gas phase caused by temperature. But obviously, the values calculated using these two criteria are much higher than I expected. Why is that? I’m so confused; I can’t figure it out! I would like to ask the experienced folks for advice; thank you!
It should be calculated based on the volume of the storage tank, taking temperature differences into account. A nitrogen seal is necessary; otherwise it will definitely not be safe. Additionally, it is important to ensure a stable supply of nitrogen for the seal. Otherwise, in cases of sudden weather changes (such as heavy rain), if the nitrogen supply is insufficient, the tank can easily get deflated. Additionally, it is also necessary to ensure that the breathing valve and pressure relief manhole are safe and functional; otherwise, in bad weather or when operating conditions change suddenly, they can easily be damaged.
Thank you so much! Now I’m using a different approach for the calculation. First, check the weather conditions at the location of the project. Identify the temperature changes in extreme and average conditions. Then, the changes in the gas and liquid phases within the tank due to temperature variations are calculated using different temperature changes and various storage conditions of the tank. Changes in liquid phase temperature cause changes in density; calculate the volume change ； Changes in gas phase temperature are calculated using the PVT equation. In this way, for the various combined operating conditions, the maximum value calculated is about half lower than the value specified in the standards.
Thank you to the original poster for the idea; there are calculation formulas according to API2000. Is such practical calculation reliable?