air flows, compressors & diffusers

[panelman]

Guys

We have a blower producing 4000 m3/hr of air at 0.3-4 bar which feeds 4 lanes of under water diffusers. Manifold pipe is 24” dia with 8” branches to individual lanes.

When the blower is down the plan is to isolate the 8 inch pipes from the manifold and feed air (1m3/min @ 7 bar) from a diesel road drill compressor into the 8 inch pipe via a ¾” hose and claw coupling.

Any thoughts, questions or warnings from those who know better than me would be welcome

 

[StephenA]

Some initial thoughts (although not exhaustive by any means)

4000m3/hr is 66m3/min or 86m3/min free air(at 0.3 bar) and 330m3/min free air (at 4 bar) which is quite a big unit.

I presume that the road compressor is a 250cfm unit (They use volume of free air for capacity), so that you will get a lot less air at 4 bar than the main unit. It is likely that not all the diffusers will work, it depends on the water head.

You will lose a lot of pressure using a 3/4" hose and for better efficiency I would use a 2" hose, and as short as possible.

Is there an environmental issue will the oil in the road compressor?

 

[panelman]

Stephen

Forgive me but I don’t understand the terminology you are using.

The compressor people said 1m3/min @ 7 bar which I assumed would expand to 7m3/min @ 1 bar or 17.5 m3 @ 0.4 bar.

Is this correct or have I got hold of the wrong end of the stick?

 

[StephenA]

Maybe I misread your initial question which I thought read that the pressure was 0.3-4bar i.e. 0.3 to 4.0 bar, but maybe you meant 0.3 to 0.4 bar.

If the latter then it is better.

The 7m3/min is the free air volume. If you are pumping at 1 bar atmospheric plus 0.4bar (4m water depth) i.e. 1.4 bar, then you will get 5m3/min.

Best regards

StephenA

 

[panelman]

I did indeed mean 0.3 to 0.4 bar

does this mean i will get 17.5 m3 @ 0.4 bar if i expend 1 m3 @ 7 bar?

 

[StephenA]

The 0.4 bar is I take it 4m underwater i.e. absolute pressure is 1.4 bar. This means that you will get 7 divided by 1.4 equals 5 m3/min, or do you have a partial vacuum (which seems unlikely!)

Best regards

StephenA