6 replies to this topic

[astonkr]

Dear everyone,

I'd like to calculate PSV relief load for external fire case of unwetted vessel.
The recommended maximum vessel wall temperature for the usual carbon steel plate materials is 593 degC(1100 degF) based on the APR 521.

But our vessel material is Incoloy 800H(UNS N08810 : Alloys of Nickel, Iron, Chromium etc.,) and SS304L(A240 304L).
Please let me know recommended maximum vessel wall temperature for Incoloy 800H and SS304L material
.


Regards

Astonkr

[fallah]

Astonkr,

Please specify T1, i.e. gas absolute temperature at the upstream relieving pressure.

Fallah

[astonkr]

Thanks for your reply. Fallah.

Relieving condtions of the vessel with Incoloy 800H are as follows.

Operating Press. = 19.99 kg/cm2g,Operating Temp. = 525 degC
P1(Relieving Press.) = 34.3 kg/cm2A
T1(Relieving Temp.) = 1887.8 degF(=2347.8 degR)

[fallah]

Thanks for your reply. Fallah.

Relieving condtions of the vessel with Incoloy 800H are as follows.

Operating Press. = 19.99 kg/cm2g,Operating Temp. = 525 degC
P1(Relieving Press.) = 34.3 kg/cm2A
T1(Relieving Temp.) = 1887.8 degF(=2347.8 degR)

astonkr,

As far as i know, maximum permitted temperature of using Incoloy 800H is 1650 F. Hence, as per above relieving temperature the term (TW-T1) would be negative and in this situations you should take it equal to 0.01.

Fallah

[astonkr]

Dear Fallah,

You mentioned that if (Tw-T1) is negative, the term (Tw-T1) is equal to 0.01.
I saw the equations (9) and (12) on the API 521.
If F' is less than 0.01, then use a recommended minimum value of F'=0.01.
Do you mentioned that the term (Tw-T1) is equal to F'? I don't understand relationship between two equations.

Astonkr

[fallah]

astonkr,

Equations (9) and (12) both included (TW-T1) and i referred just to (TW-T1) not to F'. I meant if the term (TW-T1) become negative then use 0.01 value for this term either in equation (9) or in (12).

This rule also would satisfy the API 521 recommendation you mentioned: If F' is less than 0.01, then use a recommended minimum value of F'=0.01, because in most cases you face with a F'<0.01 you might have negative (TW-T1) rather than having very low value of F' between zero and 0.01.

Fallah

Edited by fallah, 09 April 2012 - 01:31 AM.

[astonkr]

I appreciate your help. Fallah.