API 650 bitiminous sand mixture for ring wall with sand filled or concrete floor 2

[lganga]

Dear fellows
Vendor has to construct two types of tank floors.
Concrete, for small diameter tanks and ring wall type with different type of soil filling
API 650, recommends for the ring wall a bituminous mixture, but does not says anything about the sand at inner part. For the concrete floors says nothing about a soft support for all the floor, just to get a flat surface and to seal it against water.
For concrete floor, I heard to use asphalt with sand mixture, but that can work for shop fabricated tanks, what about when you weld the floor in site?.
For the ring type support, if the tank has an slope from the center to outside diameter. Do we need to fix the sand with a bituminous mixture to get the slope?.
No spec has been written in their offer about tank seat support and water seal
I wiil appeciate your answer
Regards

 

[Duwe6]

Paint/coat shop fabbed tanks in the shop. Then when being rigged/lifted into final position on concrete pad, give the floor a further coat of coal tar epoxy. Or set the tank onto 'tarpaper' with a heavily impregnated felt -- the stuff listed as " 30# ". Lay two layers, and trim back to the chime after setting is done.

Clean sand is fine for a ringwall fill. Put it in wet, so the sand is 'hard' and easier for the tank crew to work on. Wet sand self-compacts itself fully. No further work required. Leave 2 to 5 weepholes in the lower area of the ringwall, so the excess water can drain out. If the sand is 'clean-clean' and has absolutely no rocks in the top foot, you really don't need anything else. The water in the sand will ooze out the weep holes, you've sealed around the ringwall, and the bottom will forevermore be dry.

Do not be like the idiot engineers I have built tanks for. With a lapped floor and their inevitable 3-way laps, your floor cannot be 'level'. Laying a floor on a dead-flat sand pad gives yourself a puddle of product on each and every sheet when cleaning time comes. A pain and $$$ to clean for Inspx and/or repairs. Have the sand mounded up, or dished down. That way the drainage will either go the rim of the floor, or be in an easily-vacuumed puddle in the middle of the tank. Saves time and money -- as long as the owner's engineer is not an idiot that insists on a "level floor".

 

[lganga]

duwe
thanks for your comments. I have anothte question aboout the kind of bituminous to impregnate the concrete floor in case of a shop fabricated St.Steel tanks, the impregnated paint should be free of clorides and sulfur. Can the tar epoxy paint, be formulated for that condition?

 

[Duwe6]

Haven't heard about chloride problems for s/s on concrete, but any industrial enamel or epoxy paint should work as a barrier. Neither have chlorides or sulfur as a leachable constituent.

 

[simplemath2]

A lot of practical knowledge here. Thanks Duwe6 for posting this.