Query regarding the calculation of the design storage level for internal floating roof tanks (i.e., the high liquid level alarm point)
Thread Content
This post was last edited by qren on 2010-6-25 at 12:08; for the SH3007-1999 version, the filling coefficient for floating roof tanks with a capacity of over 1000 cubic meters is 0.9； It’s simple and clear. However, in order to improve the utilization rate of storage tanks, Article 4.1.3 of the new SHT3007-2007 standard provides a formula for calculating the designed liquid level of internal floating roof tanks: h = h4 – (h2 + h5), where h4 is the maximum designed height of the floating roof (at the surface of the roof), h2 is the equivalent height corresponding to the maximum liquid inflow rate over 10–15 minutes, and h5 is a safety margin of 0.3 m. Article 5.5.2 states that the set point for high liquid level alarms should be the designed liquid level of the storage tank, which is the value of h in the above formula. My question is: I have vent holes installed on the side walls of my internal floating roof tank. This height is not deducted in the above formula, and there are also foam nozzles. Is the designed storage liquid level calculated using the above formula too high? Is the alarm setting for high liquid levels also set too high? I’d like to ask whether it’s my understanding that is incorrect, or whether this issue isn’t taken into account in the standards. Have the standard compilers considered that the wall ventilation openings and foam nozzles are all located on the top of the tank? Please ask an expert to help answer it, thank you!
This post was last edited by qren on 2010-6-25 12:08. Can someone help answer my question?
Regarding the explanatory notes for the specifications, I believe the value for the maximum height of the floating deck design is intended only as a reference. The loading coefficient is generally set at 0.9; it can also be higher than 0.9, but must not exceed 0.95. Therefore, this value can be determined through comprehensive calculation
Air vents and foam outlets are provided on the side walls; the height of h4 is below these vents and outlets. The high liquid level alarm outlet is also below h4, at a relatively low height.
The 1,000 cubic meter internal floating roof tank mentioned by the poster likely does not have a high liquid level alarm (which is sometimes required depending on the specific circumstances). In my calculations, the high liquid level alarm value for an internal floating roof tank is equal to the designed liquid level height, which is calculated as the tank wall height minus the float height minus the lower edge of the foam pipe opening, plus a safety margin of 0.3. Since there is a ventilation window, compare the height of the ventilation window with the height of the floating disk to see which is higher. If the ventilation window is higher than the float, then the float height in the formula should be replaced with the height of the ventilation window ； If the floating disk is higher than the vent window, then it can be calculated using the formula. If there are any errors, please point them out, dear sea friends.