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Tips & Tricks no. 6 - How to adjust the air flows
After we discussed how to calculate the correct total
air quantity in the last issue of our Tips & Tricks, it's now time to have
a closer look at the setting procedure of the results we have obtained.Remember: The correct total air with different hose diameters
Internal hose Ø
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Powder velocity
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Total air
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9 mm
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12 m/sec
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2.7 m3/h
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10 mm
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12 m/sec
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3.4 m3/h
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11 mm
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12 m/sec
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4.1 m3/h
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12 mm
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12 m/sec
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4.9 m3/h
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Systems with automatic regulator (AFC in m3/h)
Here all you have to do is enter the total air through a keypad or by turning a swivel knob. The regulation then takes place automatically. The system operator can adjust the feed air, as required, to influence the size of the powder cloud. So that the velocity in the powder hose is kept constant, the dosage air is automatically regulated to suit.
First total air setting of manual coating systems
Injectors with orifice
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The total air of plants with manual pressure
control valves is somewhat more complex to adjust, depending on the configuration
installation. Let's take a look at it on the basis of a concrete example
with the following values: |
| Injector: |
PI-PF with orifice (recognizable from the black
or partly black dosage air fitting) |
| Hose length: |
6m / 20ft |
| Hose inside Ø: |
11 mm |
| Powder velocity: |
12 m/s / 40 ft/s |
| Total air: |
4.1 Nm3/h |
| Powder: |
Epoxy Polyester (E/P) |
| Target powder quantity |
100 g/min |
- Adjust the feed air until the desired powder cloud
is obtained (e.g. 1 bar / 14.5 PSI).
- Check the feed pressure on the pressure gauge. The
corresponding feed air quantity in Nm3/h can be read on the outer scale of
the pressure gauge.
- Calculate the dosage air quantity:
Total air (4.1 Nm3/h) - feed air (2.0 Nm3/h) = dosage air (2.1 Nm3/h)
- Now find the equivalent of the dosage air quantity
on the pressure gauge and adjust accordingly (2.1 Nm3/h = 1.5 bar / 21.75
PSI).
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| Feed air |
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Dosage air |
Increasing the powder throughput
- Increase the feed air until the desired powder cloud
is obtained (e.g. 2 bar / 29 PSI).
- Check the feed pressure on the pressure gauge. The
corresponding feed air quantity in Nm3/h can be read on the outer scale of
the pressure gauge.
Total air (4.1 Nm3/h) - feed air (3.2 Nm3/h) = dosage air (0.9 Nm3/h)
- Now find the equivalent of the dosage air quantity
on the pressure gauge and adjust accordingly (0.9 Nm3/h = 0.7 bar / 10 PSI).
These settings apply to our example and can significantly
vary depending on the hose length, the specific weight of the powder and other
parameters.
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| Feed air |
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Dosage air |
Injectors without orifice
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Injectors without orifice are generally
used with automatic air flow control. They are less suitable for systems
with manual air adjustment. The setting range of the dosage air is very
narrow here and adjustments become a rather painstaking task.
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This is how the dosage air would have to be set for the
two examples above:
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| 2.1 Nm3/h Dosage air |
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0.9 Nm3/h Dosage air |
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North America
