jamesbanda
Chemical
- Sep 21, 2004
- 223
Dear all,
I'm valiading if we drop the opperating pressure on a deep vacuum condenser if we will damage the exchanger. Aspen EDR suggests vortex shedding amplitude and turbulent buffeting issues. It says possible in some and defines them for other points on the shell the magnitudes are 1200 angstrom and 900 angstron where as the TEMA limit is 3810000 I had to convert to angstom units so i stop aspen showing me a zero for the actual values.
“Lock-in” occurs when the excitation frequency comes within 20% of the characteristic frequency. For the Shell&Tube analyses this is reported in the Table of Vibration Predictions of the full Vibration Output.
The program also states it will give warnings if any of the 4 occour.
0.8 < FV / FN < 1.2 : 0.8 < FV / FA < 1.2 : 0.8 < FT / FN < 1.2: 0.8 < FT / FA < 1.2
Where: FV Vortex Shedding; FT Turbulent Buffeting ;FN Natural FrequencyFA Acoustic Resonance
At several locations we get 2 of the 4 giving a warnings.
When i read the help files it suggests these are the kind of warnings/issues that will be seen over 10 years. So, my questions are..
1. Do i go ahead and just try operating and deep vacuum, (we dont have a spare HX), it is repareable, but downtime risks.
2. Consider for next major outage installing antivibration technology - but these look like they are risky.. and should'nt i just design it properly first..
3. Best option is re-design. I'm operating down to 2mbarA so vibration avoidance is hard..
I'm valiading if we drop the opperating pressure on a deep vacuum condenser if we will damage the exchanger. Aspen EDR suggests vortex shedding amplitude and turbulent buffeting issues. It says possible in some and defines them for other points on the shell the magnitudes are 1200 angstrom and 900 angstron where as the TEMA limit is 3810000 I had to convert to angstom units so i stop aspen showing me a zero for the actual values.
“Lock-in” occurs when the excitation frequency comes within 20% of the characteristic frequency. For the Shell&Tube analyses this is reported in the Table of Vibration Predictions of the full Vibration Output.
The program also states it will give warnings if any of the 4 occour.
0.8 < FV / FN < 1.2 : 0.8 < FV / FA < 1.2 : 0.8 < FT / FN < 1.2: 0.8 < FT / FA < 1.2
Where: FV Vortex Shedding; FT Turbulent Buffeting ;FN Natural FrequencyFA Acoustic Resonance
At several locations we get 2 of the 4 giving a warnings.
When i read the help files it suggests these are the kind of warnings/issues that will be seen over 10 years. So, my questions are..
1. Do i go ahead and just try operating and deep vacuum, (we dont have a spare HX), it is repareable, but downtime risks.
2. Consider for next major outage installing antivibration technology - but these look like they are risky.. and should'nt i just design it properly first..
3. Best option is re-design. I'm operating down to 2mbarA so vibration avoidance is hard..
