Structural Integrity Evaluation of the Heat Exchangers of a Hydrocracking SPE 69504
Edén, Roberto D. Roman, Rául
Structural Integrity Evaluation of the Heat Exchangers of a Hydrocracking SPE 69504 - Dallas, Texas Society of Petroleum Engineers 2001 - Edén, Roberto D. .
The objective of this work is to evaluate the structural integrity of the feed-effluent heat exchangers of the Hydrocracking of the Luján de Cuyo Refinery, belonging to Repsol-YPF S.A. This equipment operates under a hydrogen load at a pressure of 2133 psi and at a temperature that varies between 300^C (572ºF) and 400ºC (752ºF). An inspection performed during the plant maintenance shutdowns revealed several cracks on the channel of one of the equipment. These cracks had a depth of 2.4 in and a length covering almost all the circumference of the channel. It was concluded after several studies that during the 27 years service period and being exposed to temperatures of above 300ºC (572ºF), the material suffered an embrittlement process due to a phenomenon known as Temper Embrittlement, and that at room temperature, the material was within the range of brittle fracture. The commencement of the crack can be associated to the presence of hydrogen, to the effects of local stress concentration and to the plant maintenance shutdowns. It was estimated that probably the growth of the cracks was produced by the thermal stresses originated during the plant starting and the plant maintenance shutdowns, and that it is facilitated by the embrittlement of the material and by the presence of hydrogen. A risk evaluation was performed to analyze the feasibility of the continuous operation of the equipment under the described metallurgic conditions. By accepting a criterion of risk decision, it was concluded that the operation under such conditions was "not desirable" and that situation must be accepted by a high rank executive officer. A heat exchanger was shut down from service and used to perform several tests to determine its condition and therefore to provide the necessary technical background to the management decision making. This study was highly significant because the remaining four heat exchangers were in similar metallurgical conditions than the equipment removed from operation and they should continue with their service operation. Several studies were performed such as Charpy V tests, fracture tests and stress analysis calculations to determine the value of the stress intensity factor (J). These studies were then used as technical background and support material for decision making in regards to the continuity of the service operation of the equipment for a certain period of time and under certain operational conditions.
Structural Integrity Evaluation of the Heat Exchangers of a Hydrocracking SPE 69504 - Dallas, Texas Society of Petroleum Engineers 2001 - Edén, Roberto D. .
The objective of this work is to evaluate the structural integrity of the feed-effluent heat exchangers of the Hydrocracking of the Luján de Cuyo Refinery, belonging to Repsol-YPF S.A. This equipment operates under a hydrogen load at a pressure of 2133 psi and at a temperature that varies between 300^C (572ºF) and 400ºC (752ºF). An inspection performed during the plant maintenance shutdowns revealed several cracks on the channel of one of the equipment. These cracks had a depth of 2.4 in and a length covering almost all the circumference of the channel. It was concluded after several studies that during the 27 years service period and being exposed to temperatures of above 300ºC (572ºF), the material suffered an embrittlement process due to a phenomenon known as Temper Embrittlement, and that at room temperature, the material was within the range of brittle fracture. The commencement of the crack can be associated to the presence of hydrogen, to the effects of local stress concentration and to the plant maintenance shutdowns. It was estimated that probably the growth of the cracks was produced by the thermal stresses originated during the plant starting and the plant maintenance shutdowns, and that it is facilitated by the embrittlement of the material and by the presence of hydrogen. A risk evaluation was performed to analyze the feasibility of the continuous operation of the equipment under the described metallurgic conditions. By accepting a criterion of risk decision, it was concluded that the operation under such conditions was "not desirable" and that situation must be accepted by a high rank executive officer. A heat exchanger was shut down from service and used to perform several tests to determine its condition and therefore to provide the necessary technical background to the management decision making. This study was highly significant because the remaining four heat exchangers were in similar metallurgical conditions than the equipment removed from operation and they should continue with their service operation. Several studies were performed such as Charpy V tests, fracture tests and stress analysis calculations to determine the value of the stress intensity factor (J). These studies were then used as technical background and support material for decision making in regards to the continuity of the service operation of the equipment for a certain period of time and under certain operational conditions.
