Training cession

1
PREVOST The air
Training cession
Air and compressed air
2005
2
What is compressed air ?
Compressed air is air kept at a higher pressure
than the ambient atmosphere
Compressed air contains air, but also, oil,
water, dust and pollution.
When compressed, air always tries to return to
the ambient atmospheric pressure.This reaction
can be used as a source of energy
Training cession
Air and compressed air
2005
3
What is pressure ?
Absolute pressure is the difference between zero
and the compressed air pressure
Effective pressure is the difference between the
ambient atmospheric pressure and the compressed
air pressure (this is the measurement we use in
our field)
Pressure is a force acting on a surface per
unit of area
Atmospheric Pressure is the difference between
the absolute zero (full vaccum) and the pressure
at the sea level (1.013 bars, 14.7 psi)
Training cession
Air and compressed air
2005
4
What is pressure ?
Bar x 1.019 kg/cm2
Bar x 100.00 pa
Kg / cm² x 0.981 bar
Bar x 14.5 psi
Kg / cm² x 0.07 psi
Psi / 14.5 bar
1 pound 453.6 g
Training cession
Air and compressed air
2005
5
What is flow ?
Flow is the measurement of the quantity of fluid
or gas going through a certain section and for a
certain time
Flow can be mesured in scfm, m3/h, m3/mn, l/h,
l/mn, l/s, etc
Flow can be the measurement of the produced air
(from the compressor) or of the consumed air (by
the tool )
Training cession
Air and compressed air
2005
6
What is the pressure drop ?
Compressed air

Atmospheric pressure
DP is the difference of pressure between P1 and
P2 If P1 P2 then the flow is 0. If P1gtP2 then
the flow is gt0. The more opened is the valve ,
the lower is P2 and the higher is ?P and the flow.
Training cession
Air and compressed air
2005
7
What is flow ?
CV x 7 m3/h
KW x 10 m3/h
CV H P x 1.015
H P CV x 0.98
H P x 4.5 cfm
(m3/h x 273) / (273 c) Nm3 / h
Nm3 / h x (273 C) / 273 m3/h
Training cession
Air and compressed air
2005
8
What is flow ?
a by the opération b
B
A
Training cession
Air and compressed air
2005
9
Leakage losses
A small leak can reduce efficiency and waste
power.
No more than 5 of the compressor capacity
should be allowed for leakage
The entire system should be checked for leakage
at regular intervals.
Common leakage points are hose connections,
couplings and valves
Training cession
Air and compressed air
2005
10
Leakage losses
Flow in M3/h at temperature 20C
Diamètre en mm
Anyone who has been in an empty workshop at the
end of a shift will be aware of the sound of
leaking airlines.
M3/h
Pression en bar
Training cession
Air and compressed air
2005
11
Leakage losses
The most commun leakage is the conection plug -
coupling
2 couplings leaking represents 1mm² At 6 bar, it
corresponds to 3.75 m³/h 1 m³/h cost is 0,006
(energy amortisment)
Considering 24 hours during 365 days leak, it
will be a total of 52,56 lost. Which means
about 26,28 per coupler !
Training cession
Air and compressed air
2005
12
Leakage losses

• Cost of a 90 cfm installation
• 4000 hrs per year
• Over 15 years

Training cession
Air and compressed air
2005
13
Did you know that ?
Each bar of excess (unnecessary) pressure costs
6 to 10 more energy !
70 of the production cost for compressed air is
energy cost !
A 15 Cv compressor delivering 100m³/h cost 1440
uro of electricity per year !
Training cession
Air and compressed air
2005
14
Consumption table
To obtain the real consumption, apply the
coefficient to the indicated consumption
Training cession
Air and compressed air
2005