Sawsan311
Chemical
- Jun 21, 2019
- 303
Dear All,
for a conservative estimate of the settle out conditions, we need to ensure that the result conditions are properly reflecting the dynamic scenarios occuring prior to and even post compressor settle out conditions. For example, in case post a trip of compressor (under settle out) a restart is required, then if the settle out pressure is underestimated, flaring is required at the suction for meeting the following:
- preventing compressor trip during start-up under discharge PSHH or PSV popping.
- reducing the motor torque requirement as well as the seal gas system load to bring the compressor seal system to the settle out pressure.
Therefore, do you agree with the following conservative basis for estimating settle out as starting conditions:
a- suction side is on PSHH since compressor may have have reached settle out conditions with eventual trip by discharge PSHH under a blocked outlet scenario. suction upstream system is packed with no credit for any flaring on the upstream side.
b- before compressor stops it would have evidently speeded up by the recycle operation hence discharge side pressure shall consider the resulting pressure from an increase in speed by 105% to 110%
c- any cooler system would have stopped by compressor trip through ESD--> basis for settle out temperature.
Some consultants tend to consider normal suction pressure at the starting pressure instead of PSHH , do you agree that this basis is not conservative since specially in multi stage compressors, a blocked outlet would cause all stages in run under recycle with a concurrent increase in speed?
Additionally, even if an upstream system involves a production separator, in case it trips under PSHH, compressor would subsequently go into recycle mode with the initial pressure being that PSHH...
Appreciate your views and discussions.
for a conservative estimate of the settle out conditions, we need to ensure that the result conditions are properly reflecting the dynamic scenarios occuring prior to and even post compressor settle out conditions. For example, in case post a trip of compressor (under settle out) a restart is required, then if the settle out pressure is underestimated, flaring is required at the suction for meeting the following:
- preventing compressor trip during start-up under discharge PSHH or PSV popping.
- reducing the motor torque requirement as well as the seal gas system load to bring the compressor seal system to the settle out pressure.
Therefore, do you agree with the following conservative basis for estimating settle out as starting conditions:
a- suction side is on PSHH since compressor may have have reached settle out conditions with eventual trip by discharge PSHH under a blocked outlet scenario. suction upstream system is packed with no credit for any flaring on the upstream side.
b- before compressor stops it would have evidently speeded up by the recycle operation hence discharge side pressure shall consider the resulting pressure from an increase in speed by 105% to 110%
c- any cooler system would have stopped by compressor trip through ESD--> basis for settle out temperature.
Some consultants tend to consider normal suction pressure at the starting pressure instead of PSHH , do you agree that this basis is not conservative since specially in multi stage compressors, a blocked outlet would cause all stages in run under recycle with a concurrent increase in speed?
Additionally, even if an upstream system involves a production separator, in case it trips under PSHH, compressor would subsequently go into recycle mode with the initial pressure being that PSHH...
Appreciate your views and discussions.
