Foundation Control

[TANKO]

Hi 1000$ for the correct answer
I d like to understand better the chapter 7.5.5.2 & 7.5.5.3 about foundations control before erection.
For 7.5.5.2 should we check only the contour?????It seems clear.
For 7.5.5.3 it talks about "specified high point" What does it mean?Is it an external point to refer to?
shall we check only the contour?Or the slope to?It is not very clear.

Thank you in advance

 

[IFRs]

7.5.5.3 is for foundations whose top surface is not in a horizontal plane. This is sometimes referred to as a "shovel slope". In this case, the foundation has a high point and 180 degrees away is a low point. The tank is installed vertical but the floor slopes from one side of the tank to the other. When emptying the tank, the last bit of liquid will flow to the low side. In all cases, a concrete foundation needs be + or - 1/8 inch from the required elevation in any 30 feet and + or - 1/4 inch from the required elevation for the entire circumference. When the foundation is level, measuring deviations is easy since a single benchmark can be used. When the foundation slopes it is a little harder but the concepts are the same.

 

[TANKO]

ok for a ringwall concrete foundation with internal slop in sand...shall i follow chapter 7.5.5.2 or 7.5.5.3??

 

[IFRs]

Since the ring wall is intended to be flat and level, you follow 7.5.5.2

 

[TANKO]

ok it is clear....i thought to follow 7.5.5.3...yes, the ring wall is a horizontal plane.
I m implementing a work instruction for the foundation check according to EN 14015 & API 650 for my company.

Thanks

 

[Duwe6]

Further thought TANKO, a 'level' tank floor will not drain due to all the lapped floor plates. Crown the sand slightly to make the final dregs end up at the walls. Or slightly depress the sand to have the dregs puddle in the center.

I like the center best -- easy for the Vac Truck to suck out the last liquid when cleaning the tank for entry.

 

[IFRs]

Duwe6 - You are right - some slope is good. API suggests 1 in 120 slope up to the center if the purchaser does not specify. I think Tanko said there was a slope in the sand inside the ringwall. I'm seeing more shovel bottoms now, not sure why - may be just a flash-in-the-pan.

 

[TANKO]

IFRs, it is correct what you say..there is a slope (3%)of sand towards the center inside the ringwall. We have erected 20 tanks near Rotterdam on this kind of foundation.