A　temperature-jump　accident　occurred　in　the　inspection　and　repair　process　of　a　propylene　purifier　in　a　chemical　plant.　To　make　sure　if　the　purifier　can　operate　safely　after　the　temperature　jump,　a　comprehensive　safety　evaluation　using　several　methods　was　implemented.　Hardness　measurements　and　metallographic　examinations　indicated　that,　in　the　burnt　area　due　to　temperature-jump,　the　hardness　dropped　by　30%,　the　grain　size　became　larger,　and　the　colony　of　pearlite　structures　occurred.　No　crack　was　detected　by　ultrasonic　inspection.　The　strains　during　the　hydro-test　were　obtained　using　strain　gauge　in　the　burnt　areas.　The　stress　concentration　was　online　monitored　by　metal　magnetic　memory　nondestructive　testing.　When　the　hydraulic　pressure　reached　3.2　MPa,　namely　1.28　times　of　the　working　pressure,　water　escaped　from　the　seal　ring　of　safety　valve,　and　at　that　time　the　working　strain　in　the　burnt　area　did　not　reach　the　metal　yield　limit.　Strength　analysis　showed　that　the　safety　factor　was　approximately　1.80.　It　was　also　shown　that　there　exist　stress　concentration　zones　in　the　burnt　areas.　According　to　the　results,　the　rehabilitated　purifier　can　be　put　into　use,　but　overpressure　operating　must　be　avoided　and　safety　monitoring　must　be　performed　regularly.