3 replies to this topic

[go-fish]

I am not very clear on the concept about the ocnept of external (vacuum) pressure as used by API 650 and API 620. My understanding is that the normally the external pressure shall not exceed 1 inch of water for these tanks.

However, as per the Section 5.2.1 of API 650, Design External Pressure (Pe): Shall not be less than 0.25 kPa (1 in. of water)

Also as per Section 5.4.1 of API 620, The maximum partial vacuum shall be at least 1 in. wc.


Am I perceiving the external pressure or vacuum in same way as the API standards? The way I am interpreting is that if pressure inside the tank is atmospheric then external pressure can be maximum 0.25kPag.

[fallah]

The way I am interpreting is that if pressure inside the tank is atmospheric then external pressure can be maximum 0.25kPag.

go-fish,

The way you are interpreting can conceptually be correct...but:

It really means if the pressure outside the tank is atmospheric then the pressure inside the tank can be maximum 0.25 kPa lower than atmospheric.

Fallah

[go-fish]

Fallah:

Based on your explanation, can it be said that the vacuum limit is - 0.25 kPag at most?

But how do I then interpret the "at least" criteria instead of "at max" criteria of the API standards

Edited by go-fish, 13 May 2012 - 04:22 AM.

I'm facing the same problem with go-fish about this ambiguity. Anybody can help us?.

Thanks