A　temperature-jump　accident　occurred　because　of　wrong　operations　for　a　propylene　purifier　in　a　chemical　plant.　To　make　sure　if　the　purifier　can　be　operated　safely　after　the　temperature　jump,　a　series　of　testing　and　strength　safety　evaluation　were　implemented.　Because　the　direct　testing　of　mechanical　properties　of　the　purifier　was　not　available,　hardness　measuring,　metallographic　examinations,　ultrasonic　inspection　and　hydro-test　were　performed,　respectively.　Simultaneously　with　hydro-test,　stress　measuring　and　metal　magnetic　memory　nondestructive　testing　(MMMT)　which　can　describe　early　defect　were　applied.　The　results　showed　that,　due　to　temperature-jump,　in　the　burnt　area　the　grain　size　became　larger,　the　colony　of　pearlite　structures　occurred,　the　hardness　dropped　by　30%　and　magnetic　signal　became　abnormal　as　the　stress　increased.　In　order　to　monitor　the　magnetic　change,　the　second　MMMT　was　performed　after　the　purifier　had　worked　for　a　month.　It　is　indicated　that　the　reserve　strength　declined,　the　Tresca　stress　safety　factor　with　normal　working　pressure　of　2.5　MPa　was　about　1.92,　several　stress　concentration　existed　in　the　burnt　area　and　the　level　of　stress　concentration　increased　a　month　later.