Thickness of spades, spectacle blinds or line blanks for various pressure-temperature ratings are defined in ASME B16.48 - "Line Blanks".

This online calculator can be used to calculate custom spade/blank thicknesses for ASME B16.5 Class 2500 RF/FF flanges from sizes DN15 to DN300 using spiral wound gaskets and for a range of materials. Select the appropriate material from the drop-down and enter the design pressure, design temperature and corrosion allowance values to calculate the spade 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.

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 spiral wound gaskets for following sizes and ratings -
ASME B16.5 flanges: Class 2500 up to 12" (DN300).

Sr.No Nom
Pipe
Size
Nom
Pipe
Dia
ID (mm)
Minimum
(mm)
Corrosion
Allowance
(mm)