asprofos
Mechanical
- Mar 26, 2007
- 8
Hi,
I have been checking some calculations done for a vacuum insulated vessel. My question is if the vacuum around the inner vessel should affect the pressure vessels calculations.
It seems that 2 different manufacturers, we have worked with, have treated this differently.
As I see it if the outer vessel is self supported then the design pressure that the inner tank needs to be designed for is increased by about 14.7psi. This compared to a vessel with no vacuum insulation. I see here that the vacuum must be plugged in the calculations.
Another case would be the outer vessel is supported by the inner vessel. Then any vacuum that is created between the inner and outer will create stresses on the inner surfaces that cancel out each other. This can happen if the outer vessel is supported by the inner with forces evenly distributed on the surface of the inner. But I am pretty sure that ASME VIII would disregard even this case .
In other words, I am asking if the design pressure, in all cases, should be= Max Operating Pressure + Vacuum + Product Weight + Vessel Weight. No seismic, wind or other loads to be considered.
Thanks!
I have been checking some calculations done for a vacuum insulated vessel. My question is if the vacuum around the inner vessel should affect the pressure vessels calculations.
It seems that 2 different manufacturers, we have worked with, have treated this differently.
As I see it if the outer vessel is self supported then the design pressure that the inner tank needs to be designed for is increased by about 14.7psi. This compared to a vessel with no vacuum insulation. I see here that the vacuum must be plugged in the calculations.
Another case would be the outer vessel is supported by the inner vessel. Then any vacuum that is created between the inner and outer will create stresses on the inner surfaces that cancel out each other. This can happen if the outer vessel is supported by the inner with forces evenly distributed on the surface of the inner. But I am pretty sure that ASME VIII would disregard even this case .
In other words, I am asking if the design pressure, in all cases, should be= Max Operating Pressure + Vacuum + Product Weight + Vessel Weight. No seismic, wind or other loads to be considered.
Thanks!
