Fad

[p0689109]

If you have a 50litre compressor at ambient pressure(1bar) that equates to 88 cubic feet. So, if you then charge the compressor to 8bar (about 120psi)does that mean you have the equivalent of 704 cubic feet of air at your disposal and the higher the pressure the more you have? Also is it true that most regulators only give a maximum of 125psi? The reason I ask is that I am thinking of purchasing a compressor from the "Shiremoor compressors" company and they advertise the one I am interested in as 150psi as part of the performance package then when talking to them they say that if you/they fit a regulator that 125psi comes into play!
What are your thoughts?
Regards, MichaelT

 

[tigler]

Yes but, the pressure will drop as the air is consumed unless the compressor maintains the receiver pressure. Regulators are variable with a typical max of 12 bar, if the compressor will reach that. Also, as the reg pressure is lowered then the CFM FAD of the compressor increases, as the FAD increases with falling pressure.

 

[p0689109]

Yes but, the pressure will drop as the air is consumed unless the compressor maintains the receiver pressure. Regulators are variable with a typical max of 12 bar, if the compressor will reach that. Also, as the reg pressure is lowered then the CFM FAD of the compressor increases, as the FAD increases with falling pressure.

I thought thats what the relationship was and realise the top up restart effect. But the remark about the max regulator pressure of 125psi. by the compressor supplier surprised me. My 50L compressor has a max pressure 150psi on the data plate. The part of the regulator I was on about was a bit misleading. What I meant was the blow off valve setting, is that adjustable? I realise the regulator controls the outlet pressure to the user items and has a variable adjustment. What I want to know is can the max tank pressure be adjusted to the max tank rating or am I stuck with the 120psi?
Regards, Michael T

 

[voipio]

A 50 litre receiver is 1.77cu.ft, in old money, not 88 cu.ft.

Most compressors tend to reach 110-150psi at cut-off point and restart at around 80-110psi. A regulator capable of delivering 125psi would not deliver constant pressure when set to it's maximum, since it's supply pressure will, for part of the time, be less than the regulator's set pressure.

 

[tigler]

What I meant was the blow off valve setting, is that adjustable? I realise the regulator controls the outlet pressure to the user items and has a variable adjustment. What I want to know is can the max tank pressure be adjusted to the max tank rating or am I stuck with the 120psi?
Regards, Michael T

Safety valves are not adjustable, would sort of defeat the purpose However, they can be obtained in different pressure ratings. So the 125 psi could be replaced with a 150 psi, accepting that the receiver is ok for that pressure but it should be as they have a safety factor.

 

[Flathead_Dave]

What is it you want to run at more than 120 psi?

 

[p0689109]

To go back to the original thread, the more the pressure the more the FAD!
Yes you are right about the 50L equates to 1.76 cubic feet, not my entry. Its a ****** being 64 and doing maths and things!!
Regards, Michael T

 

[p0689109]

The item that controls the max tank pressure is, I think, called the pressure switch with unloader. Is that adjustable?(Its the terminology of all the bits that is the hard bit). Does this item also contain the safety valve or is that a seperate valve. I see the control system as the pressure switch sets the max usable pressure,the regulator allows a lower outlet pressure and the safety valve is the blow off if the pressure switch fails. Or is there some other system?
Regards, Michael T

 

[buckers]

The item that controls the max tank pressure is, I think, called the pressure switch with unloader. Is that adjustable?(Its the terminology of all the bits that is the hard bit). Does this item also contain the safety valve or is that a seperate valve.
Regards, Michael T

The start and stop pressures are adjustable on the pressure switch on many compressors, although I wouldn't be touching them with a bargepole. They're set at those settings for a reason !!

The safety valve is something seperate, and usually just sticks out from the receiver, elsewhere

 

[p0689109]

Thanks for that info. At last I have a grasp of the workings. I would just like to up the max pressure a touch as mine just gives 7.5 bar say to 8 bar.
Regards, Michael t

 

[MattF]

To go back to the original thread, the more the pressure the more the FAD!

How do you work that one out?

 

[p0689109]

Pressure, volume and temperature are directly related as per the combined gas law. i.e P1V1/T1 = P2V2/T2 So as you increase the pressure the volume shrinks by virtue of compressing it. As you release it from the restriction of its containment it expands giving more volume but less pressure.
Regards, Michael T