Technical Information

Foundations & Connections

Foundations
The design and construction of the tank supports and foundations are critical and should only be undertaken and supervised by competent professionals.

Ground level Tanks – In pressed steel tanks with internal bracing the side wall pressure applied by the water is converted to downward forces in the tank side walls. Maximum loads which can be considerable occur around the perimeter of the tank. Ground level tanks are commonly supported on reinforced concrete dwarf walls fitted with steel capping strips. The purpose of the capping strip is to spread the load over the full width of the support wall and to provide a level platform on which to erect the tank.

For practical reasons concrete cannot be cast with sufficient accuracy of level. The capping strips should be grouted in place before installation of the tank starts. Recommended tolerance level is +-2mm. Care should be taken to ensure that foundation walls are parallel and square to each other. They must protrude beyond the edge of the tank by a recommended distance of 150mm. The tapered top section of the wall assists in providing access for tools to fasten the tank panel flange bolts.

Elevated Tanks – are commonly founded on reinforced concrete bases with stub columns cast into excavations which are back filled after construction. The determining loads in elevated tank foundation design are dependent on the height of the tower. The determining load for low level tanks is the downward thrust and thus foundation size is governed by the soil bearing pressure. The determining load for high level tanks will be the uplift and thus the anchor effect of foundation and back fill mass will determine foundation size. Maximum up lift occurs when the tank is empty. ABECO supplies full foundation information for each elevated tank purchased to its design.

Load Terminology
Dead Load: The load created by the mass of the steel tower and an empty tank
Live Load: The load created by the mass of the water stored
Wind Load: The vertical loads (uplift and down thrust) created by the over tuning effect of wind pressure on the tank and support tower
Surge Load: The vertical loads similar to wind load created by water surging as the tower sways under wind load

Circular Tanks – It is important to note that our circular tanks do not require concrete foundations and can be installed on a flat, level and stable site covered by a bed of sand. If a concrete base is required – a standard mesh reinforcing will suffice. Slender tanks may require fastening down due to wind forces

Connections
Pipe Connection Points – are positioned as points selected by the purchaser. Manufacture does not start until this information is supplied. Designers should take care in selecting the pipe connection points to ensure that the piping will not foul tank supports or internal members.

Standard fittings:
BSP sockets
Flanges to BS4504 10 bar or SABS 1123 1000kPa welded to stub pipes
Inlet connection flanged inside and outside, otherwise flanged outside only

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