7 replies to this topic

[OVERLORD]

Hi All,

Should i consider any design pressure for a freely vented, fixed roof water storage tank. I have to design it to API 650.

Greetings

[fallah]

OVERLORD:


For atmospheric storage tank the limit would be 2.5 psig and for low pressure tank 15 psig.

[Frankdj]

OVERLORD:

You must consider an internal design pressure because of the internal pressure created in a fixed roof tank during product imports. See API 2000 for venting requirements.

Export rates and tank vacuum ratings are important too, since inadequate provision will cause the tank to be sucked in. I would recommend clarification of the required design presure and vacuum rating from the client. See Appendix L item 9 = "Design Pressure"; i.e., the client must specify this. Please also refer to the following : API 650; paragraphs 3.2.1 g and h are relevent. G indicates the maximum is 2.5 PSI(g) for an "API Atomspheric Pressure" tank. ( also see API 575 : 3.3 ). API 650: Addendum F is useful, the decision tree Fig F-1.

If you're interested in reading further to compare with other storage tank standards, you could look at BS EN 14015:2004 secion 5, table 3, from which you could perhaps take a view as to the minimum pressure and vacuum ratings that could be considered as reasonable in discussions with your client. Then use the clients' specified values in your API 650 calculations.

Hope this helps.

[djack77494]

Frank,

Your reply intrigues me. Are you saying that this standard (which I am not familiar with) provides MINIMUM acceptable internal design pressures? If so, do you know where the standard or a synopsis of this topic could be found? Thanks in advance.

[kkala]

In the tank data sheet you can write:

Design pressure = ATM,; that is, atmospheric,
Max incoming flow = ... m³/h,
Max. outgoing flow = ... m³/h.

Maximum & minimum ambient temperature should be also specified. The tank supplier will then size the vacuum & relief vents, so that API 650 requirements (e.g. internal P<2.5 psig, explained by Frankdj) can be satisfied. It is noted that pressure in the empty space of the tank is slightly above atmospheric on filling and slightly below atmospheric on emptying.

Alternatively, you can size above vents by yourself. Concerning API codes, you can start from <http://www.eng-tips....er.cfm?pid=809> and search the subject. A lot of firms have API 650 and API 520. However some knowledge of vent sizing is needed to check tank supplier data, when it arrives.

[Qalander (Chem)]

Dear Djack Hello/Good afternoon,

I just googled and found the link This page shows Max. Pressure, Maximum Vacuum figures you may see yourself.

http://books.google....essures&f=false

Just another link:
http://books.google....epage&q&f=false

Hope this proves clarifying/ helpful!

Edited by Art Montemayor, 20 November 2010 - 09:57 AM.

[djack77494]

Thank you, Qalander

[Renier]

See API 650 Eleventh edition June 2007 Section 5.2