5 replies to this topic

[process_persia]

Hi,

I was checking the datasheets for a deethanizer column and its reflux drum which you can see in the attached file. the MDMT for reflux drum is -80°C however, MDMT for the Deethanizer column is determined as -48°C. why there is this difference when the same liquid in the reflux drum flows back into the column?

Attached Files

•  MDMT.xlsx   47.78KB   125 downloads

[Eprocess]

Hi,

I was checking the datasheets for a deethanizer column and its reflux drum which you can see in the attached file. the MDMT for reflux drum is -80°C however, MDMT for the Deethanizer column is determined as -48°C. why there is this difference when the same liquid in the reflux drum flows back into the column?

MDMT has nothing to do with the service. but its determined according to the material of construction from ASME VIII UG-20 . so probably they are not made from same material.

[process_persia]

Hi,

I was checking the datasheets for a deethanizer column and its reflux drum which you can see in the attached file. the MDMT for reflux drum is -80°C however, MDMT for the Deethanizer column is determined as -48°C. why there is this difference when the same liquid in the reflux drum flows back into the column?

MDMT has nothing to do with the service. but its determined according to the material of construction from ASME VIII UG-20 . so probably they are not made from same material.

Sorry but I think I am a little bit confused. So, what is the temperature for which we run a dynamic depressurization to determine it? isn't it MDMT? or it's the minimum design tempreture?

[fallah]

Sorry but I think I am a little bit confused. So, what is the temperature for which we run a dynamic depressurization to determine it? isn't it MDMT? or it's the minimum design tempreture?

Dynamic depressurization determines MDMT and MDT (minimum design temperature) would be MDMT minus the margin value as per relevant process sizing criteria.

Difference between MDMT of Deethanizer column and relevant Reflux drum isn't confusing because each one would be depressurized through its own BDV while has been isolated from another one and different peak flowrates of depressurization leaded to different MDMT in those equipment.

[Root]

Sorry but I think I am a little bit confused. So, what is the temperature for which we run a dynamic depressurization to determine it? isn't it MDMT? or it's the minimum design tempreture?

Dynamic depressurization determines MDMT and MDT (minimum design temperature) would be MDMT minus the margin value as per relevant process sizing criteria.

Difference between MDMT of Deethanizer column and relevant Reflux drum isn't confusing because each one would be depressurized through its own BDV while has been isolated from another one and different peak flowrates of depressurization leaded to different MDMT in those equipment.

Fallah,
Better to determine Process parameter for coincident temp and then go for MDMT because MDMT is not giving you worst case design guide lines.
Cheers

[fallah]

Fallah,
Better to determine Process parameter for coincident temp and then go for MDMT because MDMT is not giving you worst case design guide lines.
Cheers

Toor,

About the equipment operating at a temperature below 0.0 degree of centigrade you are right,but normally for equipment operating above 0.0 degree of centigrade MDMT gives worst case design guidelines.