Spherical tanks: Discussion on the design parameters of spherical tanks
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This post was last edited by Feng Chuixiaodingding on 2015-12-7 at 12:52. There are two spherical tanks, both with a capacity of 2,000 cubic meters. For Medium 1, the design pressure is 1.77 MPa; the saturated steam pressure at temperatures of 40°C and 50°C is 1.46 MPa. For Medium 2, the design pressure is also 1.77 MPa, but the saturated steam pressure at 40°C and 50°C is 1.81 MPa. All other conditions are basically the same. I would like to ask that since the thickness of the spherical tanks and other parameters are determined based on the design pressure and temperature, what difference will it make if the saturated steam pressures for these two media differ at 50°C? What are the impacts? My understanding is that, for example, the saturated vapor pressure of Medium 2 at 50 degrees is 1.81 MPa (gauge pressure), which is higher than the design pressure of 1.77 MPa. However, the safety valve is set to a value of 1.77 MPa or less; thus, when the operating temperature exceeds 40 degrees, the pressure rises to near 1.77 MPa and then relief occurs, without reaching the saturated vapor pressure of 1.81 MPa at 50 degrees. Therefore, the saturated vapor pressure value at 50 degrees specified in the design parameters has no impact on the design of the spherical tank, right? In the case of medium 2, can’t the design temperature be set at 50 degrees? ?
Since the design pressure is 1.77 MPa and the temperature is 40 degrees, the goal is to reduce costs associated with the steel plates. In such a situation, has the design taken into account the possibility that the temperature might exceed 40 degrees? Measures such as spraying should be considered; it certainly isn’t appropriate to rely on safety valves, as that would just result in unnecessary expenses. Additionally, the steel plates are rounded up when calculated using a design pressure of 1.77, so the actual load-bearing capacity is definitely higher than 1.77. Theoretically, at 50 degrees, steel plates with 1.81 MPa should be thicker, but since the pressure difference is small, there isn’t much difference in the thickness of the steel plates. Take a look at the detailed process flow; there should be no major issues with this one.
Guys, which company are you working for on spherical tanks?
Since the design pressure is 1.77 MPa, the saturated steam pressure at 50 degrees is listed next, meaning that the maximum operating pressure is greater than the design pressure?
Based on the pressure described by the poster, the medium in the spherical tank should be a liquefied gas or liquefied petroleum gas at room temperature. TSG R0004-2009 Safety Technical Inspection Regulations for Fixed Pressure Vessels, Article 3.9.3: The design pressure of pressure vessels for storing liquefied gases at normal temperatures shall be determined based on the operating pressure at the specified temperature. As I understand it, the specified temperature is generally 50°C. It is recommended that the original poster take a closer look at the provisions. Personally, I think the design parameters of Medium 2 deserve careful consideration.
It’s not appropriate to specify a design temperature of 50°C; if 1.77 must be used as the design value, it’s better to use 40 instead. Otherwise, the pressure would need to be increased. I haven’t done the calculations yet, but it seems the difference won’t be significant
Thank you to everyone above; I’ve also discussed this matter with others and believe that the design parameters for Medium 2 can remain unchanged. However, it’s necessary to confirm whether the maximum operating temperature is 40 degrees – as long as that temperature is maintained, there should be no problems