Regarding the ventilation issue of dome tank roofs
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Vault tanks in refineries are generally used to store heavy oil and intermediate raw materials for various units. Why are some dome tanks equipped with breather valves at the top, while others have ventilation holes? What’s the difference with this setting? Why is it designed this way? I ask all the experts to discuss and come up with suggestions – :handshake Thank you so much! This post was last edited by dayu on 2008-1-22 23:05.]
Since I have very little knowledge in this area, I would be grateful if experts could explain in detail the reasons behind such a design, as well as the differences between it and other options. Please give me as much guidance as possible; thank you!
Oil tanks storing volatile oils should be equipped with breather valves. Prevent losses due to small and large breaths. Use a vent valve for containing water and other substances that are not prone to volatilization or are difficult to volatilize.
The teacher on the 3rd floor is indeed right, but this cannot be connected to reality. In actual industrial practice, vent holes are used for atmospheric residue oil, vacuum residue oil, fuel oil, catalytic slurry, and heavy polluted oil – so which of these are volatile and which are not? Yet, roof tanks used as feed for hydrocracking processes employ breather valves, which does not make sense according to what you said. Please continue the discussion.:handshake
Clause 3.1.2 of the \"Code for Design of Tank Areas in Petrochemical Storage and Transportation Systems\" SH3007-1999 stipulates that when the flash point (closed cup) of the medium inside the tank is above 60 degrees, a vent pipe should be used； When the flash point is 60 degrees or lower, a breathing valve is recommended; such a valve must be equipped with a flame arrester and a breathing valve baffle.
Installing a breather valve is primarily aimed at addressing the breathing losses of the medium contained within the tank. Since heavy oil contains few light components, a breather valve is not necessary. Additionally, due to the high temperature of heavy oil, the hot vapor and oil are released through the vent pipe. If a small amount of water enters the heavy oil and causes boiling, it can increase the pressure inside the tank, leading to damage to the tank. In such cases, the vent holes help to reduce the rapid increase in pressure； The breather valve installed on the hydrocracking feed tank is primarily used for nitrogen sealing to prevent the oxidation of the feed.
As mentioned on the fourth floor: among atmospheric residue oil, vacuum residue oil, fuel oil, catalytic slurry, and heavy foul oil, except that fuel oil may not be a heavy oil (for example, crude oil is generally used in pipelines, while refineries usually use residue oil and heavy oil), all of these are types of heavy oils that are difficult to vaporize. Generally, ventilation holes are provided instead of breather valves.
The oil tanks used for storing asphalt in our facility are all equipped with ventilation holes
Additional note: The breather valve used for hydrogenation feedstock is to prevent the oil from oxidizing.
Generally, vent valves are installed on the tops of dome tanks that contain flammable, explosive, or toxic substances, while vents are used on the tops of tanks that do not contain such substances.
For substances with a low flash point and high volatility, breather valves are used; for those with a high flash point and low volatility, ventilation openings are used