Is it necessary to add flame arresters to the outer arch roof of stable crude oil floating roof tanks?
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Project overview: An 8,000 cubic meter crude oil storage tank; the crude oil is stable, with a vapor pressure of 0.7 kilograms, and it belongs to Category A-B. An internal floating roof tank is used; its external fixed roof is equipped with 9 circumferential vent holes and one central vent hole, as required by API-650 and GB-50341 for venting purposes. None of these openings are fitted with pipes, and they are covered with rain caps without any gas seal protection. There are no requirements specified in API650, but they are specified in SH 3007 and GB 50074. Four issues regarding the standard interpretation are discussed here: 1. Is this tank applicable to SH-3007 Article 5.1.9? Because even if flame arresters are added, it’s not possible to add them only at the central ventilation holes, as that would not be effective; therefore, 10 flame arresters need to be added. 2. Do the terms \"fixed-roof storage tanks\" mentioned in Article 5.1.9 of SH-3007 and the first paragraph of Article 6.4.7 of GB-50074 also include internal floating-roof oil tanks? 3. In the third paragraph of Article 6.4.7 of GB-50074, for \"internal floating-roof tanks used for storing liquids of Class A-B, Class B, and Class C-A and equipped with a nitrogen sealing system\", must both the type of liquid and the nitrogen sealing be in place before considering the installation of a flame arrester? 4. Does the term “vent” also cover the concept of ventilation holes like ours? Final question: For crude oil like ours, do you think flame arresters should be installed at all vent holes?
I’ve really never seen circumferential ventilation holes with flame arresters.
Yes. It’s strange; 3007 only refers to the central ventilation duct, without mentioning the circumferential ventilation holes. It doesn’t make sense, huh. I think the specification requiring circumferential and central ventilation holes is meant to ensure sufficient circulation between the inside of the tank and the external environment, so as to prevent the interior of the tank from reaching combustion limits.
This post was last edited by Liu Fengrui on 2015-11-21 at 19:57; the issue remains unclear. There is no need to install a flame arrester; this tank already has an internal floating roof with circumferential ventilation holes.
According to the regulations, there are requirements regarding the area of the ventilation holes, and they are provided for respiratory functions. Flame arresters are mainly installed on nitrogen-sealed storage tanks. Crude oil tanks certainly do not need flame arresters installed.
Four issues regarding the standard interpretation are discussed here: 1. Is this tank applicable to SH-3007 Article 5.1.9? Answer: Since it is an internal floating roof tank, clause d can be applied. It is not necessary to install it on the circumferential ventilation holes. 2. Do the terms \"fixed-roof storage tanks\" mentioned in Article 5.1.9 of SH-3007 and Paragraph 1 of Article 6.4.7 of GB-50074 also include internal floating-roof oil tanks? Answer: Generally, they do not; since it is called an internal floating-roof tank, there must be a fixed roof on the outside as well, but it is not a simple fixed roof, so it does not fit the requirements of Paragraph a of that article. 3. In Paragraph 3 of Article 6.4.7 of GB-50074, for \"inner floating roof tanks used for storing Class A B, Class B, and Class C A liquids and equipped with a nitrogen sealing protection system\", should both the type of liquid and the nitrogen sealing be in place before considering the installation of a flame arrester? Answer: First of all, clause c refers to storage tanks that use nitrogen or other inert gases for sealing and protection; the crude oil floating roof tanks mentioned by the poster do not use nitrogen sealing, so they fall outside the scope of this clause. 4. Does the term “vent” also cover the concept of ventilation holes like ours? Answer: The vent mentioned here refers only to the vent located on top of the floating disk (usually in the middle of it), and it is not the same as the circular vents surrounding an internal floating roof tank.