3.5　Thickness of Lining

3.5.1　The thickness of abrasion-resistant concrete or highly abrasion-resistant concrete for double layer heat-insulating and abrasion-resistant lining with hexmesh should be 26mm or 31mm，the thickness of abrasion-resistant concrete or highly abrasion-resistant concrete for double layer heat-insulating and abrasion-resistant lining without hexmesh should be 20mm or 25mm，and the thickness of highly abrasionresistant concrete at the locations subject to severe erosion shall be in accordance with Article 3.2.7 of this Code.

3.5.2　The thickness of single layer heat-insulating and abrasion-resistant lining without hexmesh should not be less than 80mm，and the thickness of single layer abrasion-resistant or highly abrasion-resistant lining with or without hexmesh should be 20mm or 25mm.

3.5.3　The total thickness of lining may be calculated by the following equation:

Where　ti——fluid temperature，℃；

t0——average local annual air temperature，℃；

tw——temperature of metal wall of equipment or piping，℃；

α0——coefficient of convective and radiant thermal conductivity between metal wall and air，W/（m2·K）；

δ——total thickness of lining，m；

δ1——thickness of abrasion-resistant or highly abrasion-resistant concrete，m；

λ1——coefficient of thermal conductivity of abrasion-resistant or highly abrasion-resistant concrete，W/（m·K）；

λ2——coefficient of thermal conductivity of heat-insulating concrete，W/（m·K）.

3.5.4　The thickness of heat-insulating concrete of double layer lining shall be the total thickness of lining minus the thickness of abrasion-resistant or highly abrasion-resistant concrete.