BOS 841:2021

Description

1.1 This Botswana Standard specifies requirements for the design and manufacture of polyethylene storage tanks of 2 000 litres and greater that are rotationally moulded in one-piece seamless construction. The tanks are for above-ground vertical installation and capable of containing water, liquids used in food and beverage manufacture and chemical solutions at atmospheric pressure.
1.2 The objectives of the standard are as follows:
a)to ensure secure storage of water and other liquids or chemicals;
b)to ensure that performance and workmanship of the finished tank is adequate for the intended application;
c)to ensure that fittings are suitable for the intended application; and
d)to specify design criteria and material selection.
1.3 This Standard does not provide design criteria for the following:
a) liquid contents heated above their flash points;
b) liquid contents with service temperatures above1)40 °C, or
2)The rated service temperature of the tank material;
c)superimposed pressure exceeding 0.25 m head of water or 2.5 kPa, above the maximum recommended fill level; and
d) superimposed mechanical forces such as seismic forces, wind load or agitation.
Where criteria in 1.3(a) to 1.3 (d) apply, special design consideration should be given.
The tank material supplier should be consulted where the anticipated service temperature of the liquid exceeds 40 °C.
Wall thickness for circular straight-walled tanks may be determined by hoop stress data (see 5.1.2). All other tanks should be designed by appropriate engineering design methods. These methods may include finite element analysis (FEA).
1.4 This standard does not apply to portable tanks for the transport of liquids.