What is Chain Grade?
The chain Grade is based on the nominal stress in the link at the design breaking force strength. It is calculated by taking the minimum breaking force load and dividing by two times the nominal cross sectional area of the link.
Grade = 1/10 of the minimum breaking force in newtons divided by two times the nominal cross sectional area in square millimeters.
= (MBF) / (0.005)(Pi)(d)2
Grade = 0.000689 of the minimum breaking force in lbs. divided by two times the nominal cross sectional area in square inches.
= (0.000689)(MBF) / (0.5)(Pi )(d)2
MBF = Minimum Breaking Force (lbs. or kN), sometimes we use Minimum Breaking Strength, MBS
d = chain diameter (in. or mm)
Caution: The above formulas are for round diameter links only(the area calculation may vary with different cross section), such as round cross section grade 70 chain and grade 80 chain, these chains are all transport chains.