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Flare Line Back Pressure Calculation

Flare Line Back Pressure Calculation

Flare Line Back Pressure Calculation

(OP)
Hi alls,
Flare line Back pressure calculating for different segments with equation 21, my answer is coming wrong, can any one please corrrect me.
Eq:1/M^2((p1/p2)^2-1)-Ln(P1/p2)^2
Mac=.4003
P1=.5904
P2=1.5
fl/d=.95
my answer is coming very high(33.5) while answer in example is 1.08
Thanks

RE: Flare Line Back Pressure Calculation

1.729

Good luck,
Latexman

RE: Flare Line Back Pressure Calculation

10815L,

Please take a look at your equation in the original post above, it is not the same as the equation you sent me in a personal conversation:

fl/D=1/(M2)^*((p1/p2)^2-1)-Ln(p1/p2)^2

Therefore, my answer above is not correct. I'm also not sure if the equation you sent me in the personal conversation is correct, i.e. "1/(M2)^?*((p1/p2)^2-1)"

Please take great care to give the right equation; a readily available reference, if possible; and a detailed explanation of what you are doing/hoping to accomplish so we can all be on the same page. I get the feeling you were in a hurry, or something else, when you wrote the original post.

Good luck,
Latexman

RE: Flare Line Back Pressure Calculation

(OP)
Hi Latexman,
1st why i want this calculation: I'm going to tie-in spearator with existing facility and need to calculate the pressure drop between existing and new line.
2nd: i attached arcticla from chemical engineering.com and in this article equation is used for isothermal flow which is same in api521.
But in this article equation may be not correct, further please read this article and expalin in details.
Thanks for your quick response.

RE: Flare Line Back Pressure Calculation

f = 0.0152
Leq = 17.8
D = 0.3
fL/D = 0.9019
M2 = 0.4003
P2 = 1.5

I got P1 = 1.5914. The article said P1 = 1.6234 (P1/P2 = 1.08226). I'm within 2% of their answer. Check your work.

Good luck,
Latexman

RE: Flare Line Back Pressure Calculation

(OP)
Latexman,
Then its mean, problem will be solved with first part of equation only and 2nd part of euqation no meaning becuase in final step 2nd part of equation is not coming in picture.
My confusion is in 2nd part of equation.
Thanks
10815L

RE: Flare Line Back Pressure Calculation

Do you mean:

fL/D = 1/(M2)^2*((P1/P2)^2-1) - LN(P1/P2)^2

First part

Second part is the natural logarithm of the pressure ratio squared.

Good luck,
Latexman

RE: Flare Line Back Pressure Calculation

(OP)
Sir,
my answer is same your in excel -6.4 but not able to get 1.6 positive, my problem is this part of problem but claculating the pressure drop with AGPA book equation for deltap for 100m is ok.
If you explain in more detail is very helpful to understand it.
Thanks

RE: Flare Line Back Pressure Calculation

Show your work that has the problem.

Good luck,
Latexman

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