3 replies to this topic

[go-fish]

API 650, Appendix V, provides the normal operating external pressure range as 0.25 kPa (0.036 lbf/in²) to 6.9 kPa (1.0 lbf/in²). I understand API 620 tanks stipulates the maximum partial vacuum to be at least 1 in. wc. Is there an upper limit too on the design vacuum pressure for API 620 tanks?

[fallah]

go-fish,

No. Refer to API 620, sec.5.10.5.2 in which it is mentioned 1 ounce per square inch is the upper limit of partial vacuum for liquid storing. For storing gases or vapors alone, this standard doesn't contain provisions for design of relevant tanks may subject to partial vacuum.

Fallah

[go-fish]

Does that mean for API 620 tanks storing liquids, the max. limit of vacuum (external pressure) is 4.3 mbar if my interpretation of 1 ounce per square inch vacuum is correct? However, I have seen in some previous projects, a design external pressure of 5 mbar on API 620 tanks storing hydrocarbon liquids. Is my interpretation correct or am I missing something?

Edited by go-fish, 24 April 2012 - 08:24 AM.

[fallah]

go-fish,

I think 1 ounce per inch is almost equal to 5 mbar and then this value is the max limit of external pressure in tanks under API 620.

Fallah