vv2
Mechanical
- Oct 27, 2022
- 1
Hi,
I am new to this forum and in need of some help and assistance.
The company I work for builds isostatic pressure vessels in accordance with ASME Section 3 Div 3.
We recently got a request for a compound vessel (2 layers for clarification if not English).
While trying to calculate the vessel I came across Faupels Formula written as such:
P=(2*YS/sqrt(3))*log*K*(2-YS/UTS)
What is confusing to me is the K value for a compound vessel how to find it..
K is defined as K=D_outer/D_inner
(D=diameter or we can use r=radius instead of diameter)
In the last compound vessel that was built at our company back in the 80's,
The senior engineer (who is out for some time due to family issues and we can't contact him)
used K'=D'/r_inner.
The way they solved for D' is by using the Tangential stress of the outer cylinder: where
TP = Test Pressure
StT = Total Tangential stress
a= r_inner
TP*(D'²+a²)/D'²-a²)=StT
Following the math, they solve for D'.
Then use it to solve for K'.
Finally, they use K' in Faupels modified Formula as such:
P=(2*YS/sqrt(3))*log*K'*(2-YS/UTS)
What I don't understand is what is D' showing us here?
Talking to the PE who signs on our paperwork he simply defined K as R3/R1=K.
Where:
R3= outer radius of the jacket
R2= the inner radius of jacket and outer radius of vessel shell
R1= inner radius of the vessel shell
Excuse me if the terminology is wrong, but to clarify, the jacket is the outer vessel that is shrunk fit around the inner vessel (vessel shell).
I was under the impression that the D' should be something like the imaginary/theoretical middle diameter would exist, or mean diameter as used in thin wall hoop calculations?
Can anyone provide any information?
I am new to this forum and in need of some help and assistance.
The company I work for builds isostatic pressure vessels in accordance with ASME Section 3 Div 3.
We recently got a request for a compound vessel (2 layers for clarification if not English).
While trying to calculate the vessel I came across Faupels Formula written as such:
P=(2*YS/sqrt(3))*log*K*(2-YS/UTS)
What is confusing to me is the K value for a compound vessel how to find it..
K is defined as K=D_outer/D_inner
(D=diameter or we can use r=radius instead of diameter)
In the last compound vessel that was built at our company back in the 80's,
The senior engineer (who is out for some time due to family issues and we can't contact him)
used K'=D'/r_inner.
The way they solved for D' is by using the Tangential stress of the outer cylinder: where
TP = Test Pressure
StT = Total Tangential stress
a= r_inner
TP*(D'²+a²)/D'²-a²)=StT
Following the math, they solve for D'.
Then use it to solve for K'.
Finally, they use K' in Faupels modified Formula as such:
P=(2*YS/sqrt(3))*log*K'*(2-YS/UTS)
What I don't understand is what is D' showing us here?
Talking to the PE who signs on our paperwork he simply defined K as R3/R1=K.
Where:
R3= outer radius of the jacket
R2= the inner radius of jacket and outer radius of vessel shell
R1= inner radius of the vessel shell
Excuse me if the terminology is wrong, but to clarify, the jacket is the outer vessel that is shrunk fit around the inner vessel (vessel shell).
I was under the impression that the D' should be something like the imaginary/theoretical middle diameter would exist, or mean diameter as used in thin wall hoop calculations?
Can anyone provide any information?