Ocena preostale čvrstoće zavarenog sfernog rezervoara sa prslinom

Abstract

Dva sferna rezervoara za amonijak (zapremine 1000 m3) su ispitana 1998. i 1999. tehnikama bez razaranja (NDT) u skladu sa Propisima za periodičnu kontrolu. Ovi rezervoari su izrađeni 1979. od čelika StE 460 prema DIN, mikrolegiranog Cr-Ni-Ti, debljine 30 mm. Uočen je veliki broj poprečnih prslina u metalu šava i uzdužnih prslina u zoni-uticaja-toplote (ZUT) i po liniji stapanja unutrašnjih zavarenih spojeva. Da bi se procenila zaostala čvrstoća oba rezervoara, ploče 500 x 500 mm, su isečene radi hemijskog, metalurškog i mehaničkog ispitivanja. Ova ispitivanja su obuhvatala detaljno određivanje žilavosti standardnih Šarpi epruveta na instrumentiranom klatnu i ispitivanja mehanike loma na standardnim SEN(B) epruvetama za ocenu žilavosti loma. Na osnovu rezultata Šarpi ispitivanja i ispitivanja mehanike loma ocenjena je preostala čvrstoća sfernih rezervoara sa prslinama.

Two spherical storage tanks for ammonia (volume 1000 m3) have been tested in 1998 and 1999 by Non-Destructive Techniques (NDT) in accordance with the Periodic Inspection Regulations. These storage tanks have been constructed in 1979 of St.E460 steel according DIN, Cr-Ni-Ti microalloyed, 30 mm thick. The large number of transverse cracks in weld metal and longitudinal cracks in heat-affected-zone (HAZ) and along fusion line of inner welded joints have been detected. In order to assess the residual strength, of both storage tanks, plates 500 x 500 mm were cut for chemical, metallurgical and mechanical testing. These testing included detailed toughness testing of standard Charpy specimens on instrumented pendulum, and fracture mechanics testing on standard SEN(B) specimens for fracture toughness evaluation. Based on results of Charpy and fracture mechanics testing residual strength of cracked storage tanks has been assessed.