Pipes, headers, drums and tubes are pressure parts in steam boiler which has cylindrical shape. Design calculation must consider stress either longitudinal stress or circumferential stress. Circumferential stress is impact from internal pressure or loads which acting around in its circumstance of cylindrical part.
Circumferential stress is designed and calculated on that part to prevent the material split or break circumferentially. Resistance force should minimum equal than circumferential force. The following formula below is the step by step to get equation of circumferential stress:
Circumferential Force = Internal Pressure x Projection Area
= Internal Pressure x phi x
/ 4 Square of Inside Diameter
= P x π x D2 / 4
Resistance Force = Circumferential Stress x Projection Area
= Circumferential Stress x phi x Inside Diameter x Thickness
= SC x π x D x t
Résistance Force = Circumferential Force
SC x π x D x t = P x π x D2 / 4
SC = PD / 4t
The equation of circumferential stress is PD / 4t while the longitudinal stress is PD / 2t. This comparison show that amount of stress longitudinal is twice higher than circumferential.