锅炉循环泵的泵壳改型与应力安全分析

Casing modification and stress safety of boiler circulation pumps

为降低生产成本,通过采用铸造生产代替锻造生产并且减小半球形压水室内径的措施对一种现有的锅炉循环泵的泵壳进行改型.采用Ansys Mechanical软件,参照ASME标准第Ⅷ-2卷,疲劳计算应用一般迈内尔(Miner)准则和雨流计算法,计算4种泵壳的静态强度使用系数和低循环疲劳使用系数.结果表明:4种泵壳的静态强度使用系数和低循环疲劳使用系数均小于1;内径减小至0.875倍时,最大静态强度使用系数减小了7%,最大低循环疲劳系数减小了84%;壁厚增大至1.375倍时,最大静态强度使用系数减小了16.3%,最大低循环疲劳系数增大了221.4%.说明选用铸造材料代替锻造材料是应力安全的;小内径可提高静态强度性能,并显著提高低循环疲劳性能;大壁厚可显著提高静态强度性能和降低低循环疲劳性能.

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 rain-flow 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 ra-dius 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.