Centrifugal compressor performance

[protons]

Hi!

Please help for understanding Centrifugal com curves and some data.
I work with Dresser Datum centrifugal back to back two stage compressor P1~27-34bar, P2~65 - 100bar.
Please look at attach LP and HP performance maps:
My questions:
1) Did the compressor stages is properly loaded or i need to increase the discharge pressure(at map 83bar).
2) Did setpoint(cross) is safety from choken region in performance maps.


BR,

 

[protons]

HP map

 

[chicopee]

To understand this graph, you should take a year of thermodynamics for engineers. The terms used in the graph are well covered in thermo and explaining them to you is outside the scope of this forum. Since your background appears to be in industrial engineering, contact a degreed M.E. in your company for further explanation of the graph.

 

[LittleInch]

You need to consider this alongside your downstream system. The HP compressor has quite a wide range of output pressure so will vary in efficiency quite a lot, with the peak efficicency coming at the higher pressure when it is doing the most work, whilst the LP unit has a much narrower range of outlet pressure so will normally run at good effiency. If you need to increase the discharge pressure to meet your system requirment then you can do it, it has nothing to do with the loading of the compressor, but this is up to your turbine control system. Currently they both take about 4 MW shaft power, but as said, the LP unit is more or less fixed and the HP unit is taking up the difference in pressure.

So long as you maintain flow and pressure within the limits of the graphs provided by the manufacturer, you should be Ok, but as always try and maintain a distance away from the edges.

As chocopee says though, these are not machines to be treated lightly without a good understanding of how they work and what the system is they are connected to as you can break tem very easily or run them very inefficiently unless you have this level of understanding.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[rotw]

Quoted
1) Did the compressor stages is properly loaded or i need to increase the discharge pressure(at map 83bar).
Unquoted
you would basically increase the discharge pressure to satisfy process needs and not the other way around.
Shortly, on your graph you are off design in speed and flow. But questions you need to ask yourself are : is this an off design operation or the main duty ? If this is the main duty why the compressor has been sized for higher head leading to currently operate at 80 % speed? Do you have a low molecular weight case in your process driving the head ?

What do you mean by loading the compressor ? The compressor has an operating map with surge/choke limits provided by the manufacturer.
What can limit your maps ? PSV, axial thurst ? You would better ask the support of a professional before doing something risky.

Quoted
2) Did setpoint(cross) is safety from choken region in performance maps.
Unquoted
As long as you are within the maps provided by the compressor manufacturer (the answer to the question would then look obvious) I don't get what has triggered your question ? what is the technical context where the question popped up ?