Minimum pressure/vacuum to be used in design
Minimum pressure/vacuum to be used in design
(OP)
To all,
I have specified, designed and purchased with many flat bottomed storage tanks in the past. Many were designed for and will always hold petro products.
However, some flat-bottomed tanks, over thier design lives have been used for a variety of services and have held a variety of liquids. Especially when located at chemical process facilities.
My question is this: for the FB (API-650 type)tanks that may see different future service, what is the design pressure and design vacuum that makes the most sense in the specification ?
I suggest +10 IWC and - 7 IWC as being reasonable for tanks that may require conservation vents in the future.
I do know that major companies such as EXXON and CONOCO have addressed this issue.
Also see:
http: //www.ast- forum.com/ ast_forum_ display.as p?post=445
http ://www.ast -forum.com /ast_forum _tree.asp? master=443
-MJC
I have specified, designed and purchased with many flat bottomed storage tanks in the past. Many were designed for and will always hold petro products.
However, some flat-bottomed tanks, over thier design lives have been used for a variety of services and have held a variety of liquids. Especially when located at chemical process facilities.
My question is this: for the FB (API-650 type)tanks that may see different future service, what is the design pressure and design vacuum that makes the most sense in the specification ?
I suggest +10 IWC and - 7 IWC as being reasonable for tanks that may require conservation vents in the future.
I do know that major companies such as EXXON and CONOCO have addressed this issue.
Also see:
http:
http
-MJC





RE: Minimum pressure/vacuum to be used in design
RE: Minimum pressure/vacuum to be used in design
If a person is used to vessel work then 1 psi seems to be a very "low" nominal pressure, so it gets specified for a 200' tank, and then the tank designers get to wrestle with it.
Something else to consider is that under the current API-650, there is already a wind uplift pressure applied, so you may inadvertently be requiring anchorage of a tank that really doesn't need anchors.
You may apply some arbitrary pressure and shift the roof design from F.4 to F.7, which throws you into a bunch of different detailing, etc.
You may also be making a roof non-frangible when in fact it could be built as a frangible roof.
A similar issue comes up on occasion when nozzle loads are specified with no basis- it's easy to specify arbitrary nominal loads that are in fact not very reasonable for the service.
A point of confusion that comes up is that on the API data sheets, there is a blank for vapor pressure of the product, which gets confused with the design pressure in the tank.