For one of the projects recently for Centrifugal compressor, vendor has proposed that suction and interstage nozzles of compressor shall be suitable for stage discharge pressure or settleout pressure which ever is higher. Vendor had taken exception to API 617 requirement of clause 4.6.4.1.1 which is approved by Consultant.
In this case there are 2 stages, so process connection nozzles are 150#/150#/150# and final discharge is 300#.
This is a fixed speed machine.
There are 3 compressors working in parallel. However the compressors are not discharging to common header directly. Downstream of compressors there are scrubbers and heat exchanger and other equipment.
1) As this is fixed speed machine can there be any scenario when the casing can see the maximum discharge pressure and will there be any concerns for mechanical integrity failure.
2) Why does API 617 require all nozzles to be suitable for MAWP. ? Is it considering the typical arrangement where centrifugal compressors are with variable speed arrangement so the discharge pressure can increase beyond rated discharge pressure? What would be premise of API to specify all nozzles to be suitable for MAWP?
3) Can the machine interstage nozzles be subjected to maximum discharge pressure incase of surge? (For this query vendor mentioned this is not possible).
Views of members are welcome.
In this case there are 2 stages, so process connection nozzles are 150#/150#/150# and final discharge is 300#.
This is a fixed speed machine.
There are 3 compressors working in parallel. However the compressors are not discharging to common header directly. Downstream of compressors there are scrubbers and heat exchanger and other equipment.
1) As this is fixed speed machine can there be any scenario when the casing can see the maximum discharge pressure and will there be any concerns for mechanical integrity failure.
2) Why does API 617 require all nozzles to be suitable for MAWP. ? Is it considering the typical arrangement where centrifugal compressors are with variable speed arrangement so the discharge pressure can increase beyond rated discharge pressure? What would be premise of API to specify all nozzles to be suitable for MAWP?
3) Can the machine interstage nozzles be subjected to maximum discharge pressure incase of surge? (For this query vendor mentioned this is not possible).
Views of members are welcome.
