3 Basic Requirements
3.1 Types of Storage Tanks
3.1.1 A low temperature steel storage tank may be a single containment tank，a double containment tank or a full containment tank.
3.1.2 A single containment tank may be a single containment tank without outer shell（Figure 3.1.2-1）or a single containment tank with outer shell（Figure 3.1.2-2）.
Figure 3.1.2-1 Single containment tank without outer shell
1-Foundation heating system；2-Foundation；3-Bottom insulation；4-Primary container（steel）；5-Flexible insulating seal；6-Suspended roo（finsulated）；7-Roo（fsteel）；8-External shell insulation；9-External water vapour barrier；10-Bund wall
Figure 3.1.2-2 Single containment tank with outer shell
1-Foundation heating system；2-Foundation；3-Bottom insulation；4-Primary container（steel）；5-Flexible insulating seal；6-Suspended roof（insulated）；7-Roof（steel）；8-Lose fill insulation；9-Outer shell（steel）；10-Bund wall
3.1.3 A double containment tank may consist of a primary container and a secondary steel container（Figure 3.1.3-1）or a primary container and a secondary concrete container（Figure 3.1.3-2）.The annular space，between the primary and secondary containers，should not be more than 6.0m.
3.1.4 A full containment tank may consist of a primary container and a secondary steel container（Figure 3.1.4-1）or a primary container and a secondary concrete container（Figure 3.1.4-2）.The annular space，between the primary and secondary containers，should not be more than 2.0m.
Figure 3.1.3-1 Double containment tank with secondary steel container
1-Foundation heating system；2-Foundation；3-Bottom insulation；4-Secondary container（steel）；5-Primary container（steel）；6-Flexible insulating seal；7-Suspended roo（finsulated）；8-Roo（fsteel）；9-Cover（rain shield）；10-External insulation；11-External water vapour barrier
Figure 3.1.3-2 Double containment tank with secondary pre-stressed concrete container
1-Foundation heating system；2-Foundation；3-Bottom insulation；4-Secondary container（concrete）；5-Primary container（steel）；6-Flexible insulating seal；7-Suspended roof（insulated）；8-Roof（steel）；9-Cover（rain shield）；10-Lose fill insulation；11-Outer shell（steel）
Figure 3.1.4-1 Full containment tank with secondary steel container
1-Foundation heating system；2-Foundation；3-Bottom insulation；4-Secondary container（steel）；5-Primary container（steel）；6-Flexible insulating seal；7-Suspended roof（insulated）；8-Roof（steel）；9-Loose fill insulation
Figure 3.1.4-2 Full containment tank with secondary pre-stressed concrete container
1-Foundation heating system；2-Foundation；3-Bottom insulation；4-Primary container（steel）；5-Flexible insulating seal；6-Suspended roof（insulated）；7-Roof（concrete）；8-Insulation on inside of pre-stressed concrete outer tank；9-Secondary container（concrete）