Safety Assessment For Penstock With Surface Pit Defects

Penstock is the important constitute of the building of water-transportation of power plant, It take on biggish inner hydraulic pressure and its own weight and watery weight. Due to manufacture or scour of loam sand when it is used, It is often appear many pit-defects on the penstock's surface. When the penstock is working, it have complica(?)d stress and create much high topical stress, it is easy create crack near the pits, this affect seriously the penstock's ability of loading. So, it is very necessary to analyze the stress and assess the safety of the penstock with surface pit defects.The pit defects belong to valume defect, so, it is not easy to analyze the stress with general methades. This paper adopt the engineering example of penstock with pit defects used in Shangheba power plant and use finite element analysis software to calculate and analyze the stresses of the pits under different orient distribution, different distance and quantity. At last,it is discussed how the pits affect the distribution of stress of the penstock.The safety of the penstock with surface pit-defects are assessed based on criterion for pressure vessels defects assessment and safety assessment for in-service pressure vessels containing defects.