Air Compression System 1

[doomster]

For a dust conveying system it uses 109.5 m³/min @6-7 bars. I have 2 existing compressors that operate at 47.26 m³/min @10 bars. I'm planning to add another compressor with the same specs with the others. Now my question is; if I install the 3rd compressor as a hot standby will the existing two compressors meet the demand or the 3rd compressor must be operating but not at 100% but only 50%?


P.S.
The existing air compression system for the dust conveying, the air supply is barely complied because the compressors always trips. When there in not enough air supply in the dust conveying system then there is another air line that can support but at only limited supply.

I attached a flow diagram of our existing compressor house layout. The teal color is for the plant wide use and the orange is for the dust conveying system.

Hoping for your opinions. Thank you!

luffy13

 

[LittleInch]

luffy,

Jus to understand this right, do you really mean 109m3/min at that pressure? It isn't common to find air volume in anything other than some sort of "standard" condition, i.e. at or close to atmospheric pressure.

If indeed these flow at pressures are correct then 47m3@10 bar is around 70 m3@ 7 bar, so two compressors would seem more than adequate to meet 109.

the apparent lack of accumulators will mean the air pressure will drop rapidly if one unit stops suddenly, but I don't really understand your question.

where does the pressure drop from 10 bar to 7 bar? If you don't have a control over pressure your compressors will be operating potentially out of curve and maybe stonewalling.

This needs a bit more explanation of the system and how it works.



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[doomster]

Little Inch, thank you for the response.

Okay i'll revise my question.
The compressors are operating at 7 bars, is it okay to increase its operating pressure to 10 bars to aid the need of the dust conveying system?
The system would require 109 m3 @7 bars. The nameplate of the compressors indicate that Full Load Package discharge pressure is 9.6 bars (140 psi) and the maximum operating pressure is at 10.3 bars (150 psi).

 

[LittleInch]

you're going to need to post the compressor curves before anyone can answer.

If they are operating at bar they may not be putting out the air you want or might be operating against the stonewall and hence this is why they trip.

Your flow and pressures seem to be a little confusing to me. much better to work in scfm...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[doomster]

Little Inch,

I'm using bar and m³ because our DCS is using and bar and Nm³
Okay let's talk in cfm units.

Compressor Specs
FAD = 1669 cfm
Compressor Power = 385 bhp
Full Load Package Discharge Pressure = 140 psig
Maximum Operating Pressure = 150 psig
Minimum Operating Pressure = 65 psig

The compressors are operating at 101.5 psig
Sorry there is no compressor curves available.
Additional info: There is a receiver tank after the compression system.

Can the two compressor meet the demand?
The usage is 3866.96 cfm

 

[LittleInch]

That makes mors sense.

However your usage figure is different from your OP.109 m3/min = 3850 ft3 This is more than double your compressor rating.

So it seems your compressors are working beyond their rated capacity hence a good reason why they are tripping.So a third compressor will help but only if you run it at the same time.

What type of compressors are thsee? How is flow controlled?

Compressor vendor should be able to supply curves.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[doomster]

Im sorry that was a miscalculation. I edited the text.

Since the compressors are operating at 101.5 psig, which is below the full discharge pressure, will it deliver higher FAD?

 

[LittleInch]

What type of compressor - piston / screw or turbine / axial?

That's why you need the compressor delivery curves and details.

Generally speaking for a centrifugal compressor then yes, lower pressure is higher FAD, but generally not very much more.

A PD compressor FAD is set by the speed of the machine so unless this this is variable then generally no.

The devil though is in the detail and whether you are in or close to the stonewall line of the compressor where even at 15 psi you still won't get anymore air through it.

Assume you've tried googling the compressor make and model? Or contacting the vendor if they are still around? Give us the details.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[doomster]

The compressor is a screw type compressor, it is an IR 2 stage compressor (HPE350-2S).
Yes I've google the compressor model but I don't have a contact of the vendor since it is bought abroad.
It is easier though if they provide the compressor curves.

Thank you for your help.

 

[LittleInch]

OK,

It looks like you have a SSR EPE350-2S screw compressor. Search on that code and you might find something more - or just call IR direct....

This table at 60htz and 140 psig for the 350hp machine matches your quote above.

The FAD at 100 psig is 1899 cfm so two is in theory 3798 cfm, not far from your requirement of 3866.

But they are operating flat out.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[LittleInch]

this is the brochure

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.