For ductile iron dismantling joint pipe thickness, it should be calculated as per below calculation formula

The minimum dismantling joint pipe thickness =(SF*PFA*DE)/(2R+SF*PFA)

SF means Factor of safety, taken as 3

PFA means Allowable working pressure of pipe ( unit is M pa )

DE means Pipe outside diameter(mm)

R means Ductile iron minimum tensile strength (M pa), take 420 M pa

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