7 replies to this topic

[jord23N]

HI EVEREBODY

I NEED TO KNOW REFERENCE ABOUT DEFINITION OF NUMBER OF DRAW OFF SUMPS FOR ATMOSFERIC STORAGE TANK BOTTOM ACCORDING API-650 DESIGN. IN ADDITION TO, THE DRAW OFF SUMP SHOULD BE CONSIDERED FOR FIRE FIGHTING WATER STORAGE TANK SERVICE? AND IS IT SO, HOW MANY DRAW OFF SUMPS SHOULD BE CONSIDER FOR A 10,000 BLS. CAPACITY STORAGE TANK.

[fallah]

HI EVEREBODY

I NEED TO KNOW REFERENCE ABOUT DEFINITION OF NUMBER OF DRAW OFF SUMPS FOR ATMOSFERIC STORAGE TANK BOTTOM ACCORDING API-650 DESIGN. IN ADDITION TO, THE DRAW OFF SUMP SHOULD BE CONSIDERED FOR FIRE FIGHTING WATER STORAGE TANK SERVICE? AND IS IT SO, HOW MANY DRAW OFF SUMPS SHOULD BE CONSIDER FOR A 10,000 BLS. CAPACITY STORAGE TANK.

In API 650 there isn't any specific statement about number of draw-off sump for storage tanks.

Number of draw-off sump is specified in each project as per project criteria considering operation/maintenance issues.For example in the project i am currently involved for the storage tank with diameter more than 30 m two sumps should be installed.

[kkala]

I NEED TO KNOW REFERENCE ABOUT DEFINITION OF NUMBER OF DRAW OFF SUMPS FOR ATMOSFERIC STORAGE TANK BOTTOM ACCORDING API-650 DESIGN. IN ADDITION TO, THE DRAW OFF SUMP SHOULD BE CONSIDERED FOR FIRE FIGHTING WATER STORAGE TANK SERVICE? AND IS IT SO, HOW MANY DRAW OFF SUMPS SHOULD BE CONSIDER FOR A 10,000 BLS. CAPACITY STORAGE TANK.

I addition to fallah's post, four (4) sumps were specified by Client here for an approx 40000 m3 slops tank (cone-up bottom).
Purpose of sumps is to collect water (and enentually other heavy impurities), which is then drawn off.
For mentioned fire water tank, there seems to be no need for sumps; bottom had better be cone down and drained (when needed) from the center.

[fallah]

For mentioned fire water tank, there seems to be no need for sumps; bottom had better be cone down and drained (when needed) from the center.

Cone down without even one sump in the middle?? If so,what about the cases no adequate positive head to drain by gravity flow?

Edited by fallah, 01 August 2010 - 12:52 AM.

[Qalander (Chem)]

For mentioned fire water tank, there seems to be no need for sumps; bottom had better be cone down and drained (when needed) from the center.

Cone down without even one sump in the middle?? If so,what about the cases no adequate positive head to drain by gravity flow?

Dear fallah,What "Kostas" said is presumably

• the normal practice for "cone down bottom design tanks" in petroleum industry;more relevant to Jet fuels for any water removal with ease.
• However most usually a pad of sufficient height is build
• to provide any reasonably needed gravitational head in almost all such cases.

As regards now-a-days common practice is

• not to have cone down design, but preferably have cone-up bottom's designs
• with minimum slope(s) an almost flat-bottom designs;
• However to cater for better water or any unwanted heavier sludge sediments' removal
• multiple sumps are incorporated in design
• even four or more might be witnessed in typical cases of
• very large diameter tanks with extremely filthy or dirty material storage service(s).

Hopefully this helps!

Furthermore as regards Firewater storage I would preferably go with

• Cone-up bottom's design
• No. of sumps would be defined by the nature of stored fire water i.e. it's
• "T.D.S.",
• "Turbidity" and/or
• "filthiness/ dirtiness" as the case might be!
• other important factor to consider might be the diameter of storage tank in question;
• to me a minimum of two sumps should be fine.
• With one connected through total draw-off line to the main pump out line.

Hope this proves useful and shows way forward.

[kkala]

Cone down without even one sump in the middle?? If so,what about the cases no adequate positive head to drain by gravity flow?

The list below concerns tanks designed in the last three years that I happened to take notice of.
Client had decided on the matter of cone-up or cone-down.

Tank usage/ Roof/ Bottom/ Sumps/ Capacity (m3)
Diesel / Conical/ Cone-up/ 4 / 20000
Naphtha / Floating/ Cone-down/ 0 / 8000
Slops/ Floating/ Cone-up/ 4 / ~20000
MTBE/ Floating/ Cone-down/ 0 / 8000
Alkylate/ Floating/ Cone-down/ 0/ 8000
Oily water/ Floating/ Cone-up/ at least 2/ 7000

Concerning above cone-down tanks, there is no sump. Drain / drawoff tube starts from the lowest part of the bottom (almost), as shown in the attached sketch “drain.xls”. Drain pipe has the possibility to be connected to a (portable) pump too.
My understanding has been that the tank bottom serves as some sort of sump in this case. Water settles down there (in bottom center), then drained manually. Is there a better design practice for cone-down tanks? I suppose that a sump below bottom center would be hard to construct.
Comments on this, including disadvantages of cone-down bottom (one can be that drain pipe gets too long, equal to tank radius), would be highly appreciated

Attached Files

•  drain.xls   24KB   282 downloads

Edited by kkala, 14 September 2010 - 12:38 AM.

[Qalander (Chem)]

Cone down without even one sump in the middle?? If so,what about the cases no adequate positive head to drain by gravity flow?

The list below concerns tanks designed in the last three years that I happened to take notice of.
Client had decided on the matter of cone-up or cone-down.

Tank usage/ Roof/ Bottom/ Sumps/ Capacity (m3)
Diesel / Conical/ Cone-up/ 4 / 20000
Naphtha / Floating/ Cone-down/ 0 / 8000
Slops/ Floating/ Cone-up/ 4 / ~20000
MTBE/ Floating/ Cone-down/ 0 / 8000
Alkylate/ Floating/ Cone-down/ 0/ 8000
Oily water/ Floating/ Cone-up/ at least 2/ 7000

Concerning above cone-down tanks, there is no sump. Drain / drawoff tube starts from the lowest part of the bottom (almost), as shown in the attached sketch "drain.xls". Drain pipe has the possibility to be connected to a (portable) pump too.
My understanding has been that the tank bottom serves as some sort of sump in this case. Water settles down there (in bottom center), then drained manually. Is there a better design practice for cone-down tanks? I suppose that a sump below bottom center would be hard to construct.
Comments on this, including disadvantages of cone-down bottom (one can be that drain pipe gets too long, equal to tank radius), would be highly appreciated

Thanks Dear Kostas it is confirmatory to our mutually shared understanding,I believe.

[kkala]

...normal practice for "cone down bottom design tanks" in petroleum industry; more relevant to Jet fuels for any water removal with ease. However most usually a pad of sufficient height is build to provide any reasonably needed gravitational head in almost all such cases.
As regards now-a-days common practice is not to have cone down design, but preferably have cone-up bottom's designs with minimum slope(s) an almost flat-bottom designs However to cater for better water or any unwanted heavier sludge sediments' removal multiple sumps are incorporated in design even four or more might be witnessed in typical cases of very large diameter tanks with extremely filthy or dirty material storage service(s). Hopefully this helps!
Furthermore as regards Firewater storage I would preferably go with Cone-up bottom's design. No. of sumps would be defined by the nature of stored fire water i.e. it's "T.D.S.","Turbidity" and/or "filthiness/ dirtiness" as the case might be! other important factor to consider might be the diameter of storage tank in question; to me a minimum of two sumps should be fine. With one connected through total draw-off line to the main pump out line. Hope this proves useful and shows way forward.

Dear Qalander,it was your previous post on the subject that caused my recent one. A few additional clarifications would be useful.
1. I have understood from your post that cone down bottoms have usually a pad at the center (like a central sump), to promote water draw off. This can get better water separation than what seen in local refineries (internal draw off pipe up to bottom center - gravitational head created by overhead fuel as long as it exists). Pad construction at the bottom center was considered by me as difficult (costy), but it may not. Is the draw off pipe internal (i.e. in the tank) or external connected to the pad?
2. A 10000 bbl fire water tank (probably of dia=16 m & H=10 m) is rather small, is it worthwhile installing sumps in it? Of course this depends on "dirtiness" of water (as you mention), but fire water probably cannot be too dirty (clogging the springlers). I assume main purpose of sumps is to collect water from stored fuels, sometimes "dirtiness", yet they need dedicated draw off lines.