When two centrifugal compressors operate in parallel, if the anti-surge valve does not close fully, does the load distribution controller play a significant role? ? ?
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I would like to ask: in a centrifugal compressor operating in parallel with two units, after manually adjusting so that the load on both units is roughly equal, the load distribution controller is activated. If at this point the anti-surge valves of both units, or those of one of the units, are not fully closed, does activating the load distributor have any real effect? Since the load distribution is adjusted based on the flow rate of the compressors, if one of the anti-surge valves is not fully closed, part of the flow will be returned. For example, if 10,000 cubic meters per hour of gas is required downstream, and one anti-surge valve is fully closed, then the flow going downstream remains at 10,000 cubic meters per hour; the other valve also has flow returning at 10,000 cubic meters per hour. From the perspective of the load distributor, the flow rate through both compressors is the same, so no further adjustment is needed. However, in terms of actual operation, this approach is certainly not efficient, as it’s equivalent to one of the compressors not being used. At this point, shouldn’t manual adjustments be made to ensure that the flow rate through each compressor is around 5,000 cubic meters per hour? The anti-surge valves should also be fully closed, after which the load distributor should be activated to supply gas to the downstream systems.
The optimal load distribution for two machines operating in parallel is one that ensures equal surge margin. In the case you mentioned, the load should be distributed such that the load on the machine equipped with a surge preventer is reduced, while the load on the machine without such a device is increased. The end result should be that neither surge preventer needs to be activated, or both of them need to be activated
Based on the poster’s example, it is practically impossible for two units to each provide a flow rate of 5000. The load distributor can only serve as a reference; the actual operation should be determined based on the current level of the main motor. If the gas volume requirement is not high, it is recommended to use only one unit, as this is more energy-efficient. If the gas volume is large, it is advisable to manually balance the gas flow from the two units first, and then use a distributor for control.