DK44
Mechanical
- Sep 20, 2017
- 196
1. In an Industrial situation, for a typical High temperature Reactor Design, we have the following critical conditions:
1.1 Design Temperature = 500 C
1.2 Working Temperature = 451 C
1.2 Design Life = 20 Years.
1.3 Materials of Construction of Vessel = Low Alloy Steel Base metal + Corrosion resistant Alloy 601 Clad inside to suit the fluid conditions . The clad metal being not considered in design.
2. For the base metal selection, we have the following options of ASME Materials.
2.1 SA 387 Gr 11 Cl 1 or Cl 2 (1.25 Cr-0.5 Mo)
2.2 SA 387 Gr 12 Cl 1 or Cl 2 (1 Cr -0.5 Mo)
3. My observations are:
3.1 SA 387 Gr 11 Cl 1 or Cl 2
a) ASME Sec II D specifies max permitted Temperature = 649 C with corresponding Design allowable stress.
b) ASME Sec II D also specified Time dependent Creep range Temp of 480 C. I understand that this time is based on 100,000 Hrs (11.4 Yrs)
c) My observation is that though ASME permits up to 649 C, the allowable stress beyond 480 C are in creep range based on creep at 100,000 Hrs (11.4 Yrs) which is less than specified design life required of 20 yrs. Hence this material is not suitable for the given Vessel from code point of view for the given service condition. It will be a deviation from the code. Client's written acceptance is needed to proceed with this material.
i) As an exception-1, can this material be evaluated for Creep Life assessment and check suitability for 20 years.
ii) As an exception-2, if the vessel will not go beyond 480 C in the life of 20 Years, can this material be accepted.
3.2 SA 387 Gr 12 Cl 1 or Cl 2.
a) ASME Sec II D specifies max permitted Temperature = 649 C with corresponding Design allowable stress.
b) ASME Sec II D also specified Time dependent Creep range Temp of 510 C. I understand that this time is based on 100,000 Hrs (11.4 Yrs)
c) My observation is that though ASME permits up to 649 C, the allowable stress beyond 510 C is in creep range based on creep at 100,000 Hrs (11.4 Yrs) which is less than specified design life required of 20 yrs. However, since the intended Design Temp of 500 C is less than the creep range of this material, this is suitable for the given Vessel.
Kindly provide your comments on my above observations.
1.1 Design Temperature = 500 C
1.2 Working Temperature = 451 C
1.2 Design Life = 20 Years.
1.3 Materials of Construction of Vessel = Low Alloy Steel Base metal + Corrosion resistant Alloy 601 Clad inside to suit the fluid conditions . The clad metal being not considered in design.
2. For the base metal selection, we have the following options of ASME Materials.
2.1 SA 387 Gr 11 Cl 1 or Cl 2 (1.25 Cr-0.5 Mo)
2.2 SA 387 Gr 12 Cl 1 or Cl 2 (1 Cr -0.5 Mo)
3. My observations are:
3.1 SA 387 Gr 11 Cl 1 or Cl 2
a) ASME Sec II D specifies max permitted Temperature = 649 C with corresponding Design allowable stress.
b) ASME Sec II D also specified Time dependent Creep range Temp of 480 C. I understand that this time is based on 100,000 Hrs (11.4 Yrs)
c) My observation is that though ASME permits up to 649 C, the allowable stress beyond 480 C are in creep range based on creep at 100,000 Hrs (11.4 Yrs) which is less than specified design life required of 20 yrs. Hence this material is not suitable for the given Vessel from code point of view for the given service condition. It will be a deviation from the code. Client's written acceptance is needed to proceed with this material.
i) As an exception-1, can this material be evaluated for Creep Life assessment and check suitability for 20 years.
ii) As an exception-2, if the vessel will not go beyond 480 C in the life of 20 Years, can this material be accepted.
3.2 SA 387 Gr 12 Cl 1 or Cl 2.
a) ASME Sec II D specifies max permitted Temperature = 649 C with corresponding Design allowable stress.
b) ASME Sec II D also specified Time dependent Creep range Temp of 510 C. I understand that this time is based on 100,000 Hrs (11.4 Yrs)
c) My observation is that though ASME permits up to 649 C, the allowable stress beyond 510 C is in creep range based on creep at 100,000 Hrs (11.4 Yrs) which is less than specified design life required of 20 yrs. However, since the intended Design Temp of 500 C is less than the creep range of this material, this is suitable for the given Vessel.
Kindly provide your comments on my above observations.