Abstract:In order to reduce manufacture cost, it is proposed to modify one boiler circulation pump by using casting method instead of forge method and reducing internal radius of semispherical casing. Based on ASME Code Section Ⅷ Division 2, using Ansys Mechanical software, adopting finite element method (FEM), Miner′s rule and rainflow counting method, static strength usage factors and low cycle fatigue usage factors of four pump casings were calculated. The calculation shows that static strength usage factors and low cycle fatigue usage factors are all smaller than 1; when the internal radius is reduced to 0.875, maximum static strength usage factor is reduced by 7%, maximum low cycle fatigue usage factor by 84%; when wall thickness is increased to 1.375, maximum static strength usage factor is reduced by 19.5%, maximum low cycle fatigue usage factor is increased by 221.4%. The results show that casting material is stress safe; smaller radius can help improve static strength and greatly reduce low cycle fatigue; and larger wall thickness can greatly help improve static strength and significantly reduce low cycle fatigue.
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