6 replies to this topic

[Chemical9]

Hello All,

What are the advantages of having inlet nozzle on top of the caustic storage tank. Are there any codes that I should consider before designing the caustic storage tanks.

Thanks.

[breizh]

Hi Chemical9 ,
Let you consider this paper from Dow chemical ,it should support your query .

http://www.dow.com/c...fety/design.htm


Hope this helps

Breizh

[Chemical9]

Breizh,

Thanks for the response. I saw that website earlier and wondering what happens if we have inlet nozzle on the bottom of the tank with some kind of check valves.

[Art Montemayor]

Chemical9:

Having dealt with and stored a lot of hazardous chemcicals - including caustic soda - I have always preferred to have - where possible - 100% roof mounted nozzles on storage tanks. The reason(s) for this is that the possibility of human contact - or liquid spillage - are essentially avoided. The only thing left to allow for liquid spillage is a main tank rupture - which is deemed not credible if one has yearly tank inspections and dikes. Of course, I have met a lot of management disapproval in the past due to the extra costs - but my response is that serious safety measures always cost extra money.

In the Dow design I suspect that they are avoiding a potential back-syphoning of caustic after terminating the tank loading or filling. With a dip pipe they have to drill a syphon-breaking hole at the top of the dip pipe, immediately under the fixed roof. I usually used a 1/2" drill to do this.

You don't state the reason for your installing a check valve on the fill line, but I suspect that you are also concerned with a back-flow. I would point out that a check valve will not "fly" in a Hazop review and, therefore, will not be accepted as a mitigation of caustic back flow. And that may well be the reason that Dow opts for top entry. That would be my guess.

[Chemical9]

Art,

I appreciate you for sharing your valuable experience. I thought of using check valve to avoid back-flow. Is it a common practice to use dip pipe inside a chemical storage tanks.

Thanks,

[Art Montemayor]

I consider the application of top entry for tank filling as essentially a "standard operating procedure" (SOP). When I worked on DuPont and Huntsman plant projects, it was basically 100% of the storage tank filling operations - and in the Dupont projects we always had a dip pipe (with a weep hole) to avoid any generation of static electricity due to liquid hydrocarbons' free-falling.

[Chemical9]

Thank you very much for the information. Are there any codes that we should consider before designing storage tanks.