4.6　Allowable Stress

4.6.1　The allowable stress of steels(including steel plates,steel pipes,forgings,etc.)used to fabricate pressure parts and bolting materials at various design temperatures shall be determined in accordance with GB 150.For design temperature below 20℃,the allowable stress at 20℃shall be taken.

4.6.2　The allowable stress of materials used to fabricate non-pressure parts shall comply with the following requirements:

a)The allowable stress of materials for skirt shell and its transition section shall be as specified in GB 150;

b)The allowable stress of the anchor bolt chair of skirt(including base ring,cover plate and gusset plate)shall be 147MPa for carbon steel and 170MPa for low alloy steel;

c)The allowable stress of anchor bolts,[σ]bt,shall comply with the following requirements:

1)[σ]bt shall be taken as 147MPa for Q235 carbon steel and 170MPa for Q345 low alloy steel;

2)[σ]bt for other steel may be determined by a safety factor(ns≥1.6 for carbon steel and ns≥2.0 for low alloy steel);

d)The allowable stress of tray floor and its support members at design temperature may be determined in accordance with GB 150;

e)The allowable stress of other steel attachments depending on their design temperatures,be determined with reference to GB 150.

4.6.3　In calculating the allowable stress of the columns fabricated by stainless steel clad plates(or weld overlay),the strength of cladding(or overlay)is normally not included,the allowable stress of base metal shall be determined in accordance with GB 150.