inammanj123
Mechanical
- Oct 11, 2013
- 103
I am preparing UDS for an ASME div-2 vessel, i have few clarification on how to sum up the loading cycles given in 5.5.2.3 of DIV-2
Following are my loading cycles:
step 1
1 Plant does need annual shutdown, so 1 Shutdown per. Therefore, total of cycles for 20 years of plant life = 20
2)2 per month Unplanned shutdowns requiring full depressurization of vessel during first year of operation = 24
3)1 per year Unplanned shutdowns requiring full depressurization of vessel after first year of operation = 19
4)Automatic shutdowns requiring full depressurization due to fire/emergency conditions, after first year of operation : 2 per year = 38
step 2
Now as per step 2 of 5.5.2.3 NΔFP = 20+24+19+38=101
step 3
The Vessel’s maximum normal operating pressure is 9.27 MPa and design pressure is 9.73 Mpa, so True variation in pressure, during normal course of operation, is not exceeding 15% of the design
pressure. secondly Given there is likelihood that emergency tripping of the pressurizing equipment e.g compressor prompting pressure variation is zero because there is no Pump or Compressor upstream, so there will be 0 cycles
step 4(this is where i need help)
The expected Type (c), temperature differential cycles (N∆TE) are estimated on the basis that there will be always Water Service at 37 °C, Desander cool down to ambient temperature. Only planned & unplanned shutdown may result in a cool down. The max. temperature differential maximum Design Temperature and Minimum Design Metal Temperature(MDMT) of 86°C will result in maximum factor of 4 as per table 5.8 at minimum ambient temperature total type (c) cycles (N∆TE) therefore are estimated to be 270. My question is how to come up with this value of 270. My approach 4(20+24+19) = 252. still doesnot add up to 270. Kindly tell how to calculate N∆TE
Following are my loading cycles:
step 1
1 Plant does need annual shutdown, so 1 Shutdown per. Therefore, total of cycles for 20 years of plant life = 20
2)2 per month Unplanned shutdowns requiring full depressurization of vessel during first year of operation = 24
3)1 per year Unplanned shutdowns requiring full depressurization of vessel after first year of operation = 19
4)Automatic shutdowns requiring full depressurization due to fire/emergency conditions, after first year of operation : 2 per year = 38
step 2
Now as per step 2 of 5.5.2.3 NΔFP = 20+24+19+38=101
step 3
The Vessel’s maximum normal operating pressure is 9.27 MPa and design pressure is 9.73 Mpa, so True variation in pressure, during normal course of operation, is not exceeding 15% of the design
pressure. secondly Given there is likelihood that emergency tripping of the pressurizing equipment e.g compressor prompting pressure variation is zero because there is no Pump or Compressor upstream, so there will be 0 cycles
step 4(this is where i need help)
The expected Type (c), temperature differential cycles (N∆TE) are estimated on the basis that there will be always Water Service at 37 °C, Desander cool down to ambient temperature. Only planned & unplanned shutdown may result in a cool down. The max. temperature differential maximum Design Temperature and Minimum Design Metal Temperature(MDMT) of 86°C will result in maximum factor of 4 as per table 5.8 at minimum ambient temperature total type (c) cycles (N∆TE) therefore are estimated to be 270. My question is how to come up with this value of 270. My approach 4(20+24+19) = 252. still doesnot add up to 270. Kindly tell how to calculate N∆TE