Thickness of spades, spectacle blinds or line blanks for various pressure-temperature ratings are defined in ASME B16.48 - "Line Blanks". However this standard covers blank thicknesses based on the full pressure rating.

This online calculator can be used to calculate spade/blank thicknesses for ASME B16.5 Class 300 and 600 Ring Joint Flanges from sizes DN15 to DN600 using Ring Joint Gaskets and for a range of materials and design conditions. Select the appropriate material from the drop-down and enter the design pressure, design temperature and corrosion allowance values to calculate the spade/blank thickness.

The thickness calculator is based on equation provided in para 304.5.3 of ASME B31.3. As per this section, The minimum required thickness of a permanent blank shall be calculated in accordance with the following equation. In the calculations below the pitch diameter of ring joint gaskets are used to calculate the spade thicknesses.

tm = dg$$\sqrt[]{\frac{3P}{16SEW}}$$ + c

where

c = sum of allowances.

dg = inside diameter of gasket for raised or flat face flanges, or the gasket pitch diameter for ring joint and fully retained gasketed flanges.

P = Internal design pressure (gauge)

S = Allowable stress of material from Table A-1 of ASME B31.3

tm = Pressure design thickness of spade calculated as per above formula

W = Weld joint strength reduction factor in accordance with para 302.3.5(e)

E = Quality factor from Table A-1A or Table A-1B of ASME B31.3

This calculation applies to flanges using ring joint gaskets for following sizes and ratings -
ASME B16.5 flanges: Class 150 and Class 600 up to 24" (DN600).

Sr.No Nom
Pipe
Size
Nom
Pipe
Dia
Pitch Dia (mm)
Minimum
(mm)
Corrosion
Allowance
(mm)
Design
Thickness (mm)
1 ... ... ... ... ... ...
2 ... ... ... ... ... ...
3 ... ... ... ... ... ...
4 ... ... ... ... ... ...
5 ... ... ... ... ... ...
6 ... ... ... ... ... ...
7 ... ... ... ... ... ...
8 ... ... ... ... ... ...
9 ... ... ... ... ... ...
10 ... ... ... ... ... ...
11 ... ... ... ... ... ...
12 ... ... ... ... ... ...
13 ... ... ... ... ... ...
14 ... ... ... ... ... ...
15 ... ... ... ... ... ...
16 ... ... ... ... ... ...
17 ... ... ... ... ... ...
18 ... ... ... ... ... ...
19 ... ... ... ... ... ...
20 ... ... ... ... ... ...