Failure of malleable cast iron sprinkler pipe end cap due to freezing of water within

Microstructure observations confirmed the ferritic malleable cast iron of the end cap. The hardness of the end cap was significantly below the hardness range specified for standard ferritic malleable cast iron. Small cracks formed during the casting of the end cap and the low strength of the end cap caused the final fracture. Failure stress determined by finite element analysis simulating the freezing of the inside water could accurately predict the failure stress and failure temperature. High tensile stress and poor manufacturing quality caused the crack to propagate in the cleavage mode and at the final stage in the ductile mode.