To exempt certain storage containers from the application of Sentence 4.3.1.2.(1), which would otherwise require the containers to conform to certain standards, if certain conditions are met [the containers are designed, fabricated and tested for the anticipated maximum working pressure, operating temperature, internal corrosion conditions and structural stresses to which they could be subjected], on the basis that these conditions provide an equivalent level of safety.
This is to limit the probability that working pressure, operating temperature, internal corrosion conditions or structural stresses will lead to failure of the storage containers, which could lead to the escape of liquid from the containers, which could lead to harm to the public.