Nitrogen sealing for internal floating roof storage tanks
Thread Content
Internal floating roof tanks are equipped with a nitrogen seal; there are currently two options: 1. Nitrogen seal + floating disk type, 2. Nitrogen seal + fully submerged honeycomb floating disk. A nitrogen seal is installed inside the tank, with a vent valve opening pressure of 1350 Pa and an emergency release valve pressure of 1955 Pa. The question is: if the additional pressure from the nitrogen seal is assumed to be 2000 Pa, will this cause the floating disk to sink? Have any known floating pad manufacturers conducted tests? My first thought was that the float tank is fine – anything that absorbs liquid will sink! Parameters: Liquid storage density 850; height of the fully submerged float disc 90 mm; diameter of the buoy-type float disc 200 mm
I haven’t considered this matter; has this happened to others in the same field?
Why isn’t anyone saying anything? Speak freely! Where are the floating pad manufacturers?
At first, I thought the buoy-type design would work fine, as it has a gas phase space in which the saturated vapor pressure of oil and gas is higher than that of nitrogen. Additionally, gas leakage occurs at the points where the buoy passes through various components, which helps to maintain pressure balance; therefore, using a nitrogen seal with the buoy-type design is a viable solution!
Theoretically, no; the gas phase pressure is transmitted to any cross-section
The vapor density at a pressure of 2000 Pa remains almost unchanged, the density difference between the gas and liquid phases stays the same, and there is no change in the buoyant force on the solids; as a result, neither type of floating pad will sink.
**Notice of the General Administration of Work Safety on Further Strengthening the Safety Management of Chemical Tank Areas, Document No. An Jian Zong Guan San [2014] 68; the document stipulates that it is strictly prohibited to allow any space to form between the floating roof of an internal floating roof tank and the material contained within it during normal operation. I’m not sure if everyone has heard of this claim; how is it implemented? The floating disc of the type mentioned by the poster doesn’t seem to meet the requirements. The original poster can consult the floating platform manufacturers; they should have the answer. If there is an answer, I hope to share it with everyone.
**Notice of the General Administration of Work Safety on Further Strengthening the Safety Management of Chemical Tank Areas, Document No. An Jian Zong Guan San [2014] 68; the document stipulates that it is strictly prohibited to allow any space to form between the floating roof of an internal floating roof tank and the material contained within it during normal operation. I’m not sure if everyone has heard of this claim; how is it implemented? The floating disc of the type mentioned by the poster doesn’t seem to meet the requirements. The original poster can consult the floating platform manufacturers; they should have the answer. If there is an answer, I hope to share it with everyone.
There is indeed such a regulation; our plant uses a fully submerged design, and it is required that the internal floating roof must not touch the bottom. If it does touch the bottom, the tank needs to be emptied first
Nitrogen sealing does not silence the floating disk, because the pressure at the upper part of the disk is also transmitted to the lower part; in other words, the medium under pressure generates an equal reaction force that lifts the floating disk.
This probably refers to the fact that the inner floating disk cannot touch the ground, right? All normal floating-type inner floating discs have oil and gas spaces