The measuring of compressed air pipeline can be done in different ways.
We suggest an example of calculation where we fix a total pressure drop of the installation at 4%.
To determinate the diameter of the tube it is necessary to know three basic parameters:
- Working pressure: The most common case for compressed air pipelines pressure is 7 bar.
- Pipeline length: It is meant as the development of the pipeline from the compressors to the most distant using point.
- Flow Rate: It can be determined knowing the consume of the equipment that need to be connected to the pipeline or knowing the declared flow rate of the compressor.
To determinate such datum we create a table which summary the indicative flow rates of compressors at 7 bar based on their power.
Indicative flow rates of the compressors to 7 bar
|
|
| KW |
CV |
Nl/min |
| 1.5 |
2 |
230 |
| 3 |
4 |
460 |
| 4 |
6 |
650 |
| 5.5 |
7,5 |
900 |
| 7.5 |
10 |
1200 |
| 11 |
15 |
1750 |
| 12.5 |
17 |
2000 |
| 15 |
20 |
2500 |
| 18 |
25 |
3000 |
| 22 |
30 |
3500 |
| 29 |
40 |
4500 |
| 37 |
50 |
6000 |
| 45 |
60 |
7000 |
| 55 |
75 |
8500 |
| 74 |
100 |
12000 |
| 92 |
125 |
15000 |
| 110 |
150 |
18000 |
| 132 |
180 |
21000 |
| 170 |
230 |
26000 |
| 200 |
270 |
31000 |
| 250 |
340 |
44000 |
|
Chose the diameter for the installation
The diagram below allows to determinate the diameter of the main line.
1 - Choose the flow rate of compressor in the Red column.
2 - Choose the distance between compressor and the most distant using point in the Blue column.
3 - Cross the lines flow rate and blue column of distance to choose the diameter.
Distance between compressor and the most distant using point.
Tube diameter for the outlets
Specifications about available tube diameters for outlets:
Ø20 with flow rate up to 1750 Nl/min
Ø25 with flow rate up to 3500 Nl/min
Ø32 with flow rate up to 6000 Nl/min
Expansion and shrinkage due to the heat
All the materials under the effect of heat variation referred to the installation temperature expand themselves as soon as the temperatur rise and shrink them when it decreases. To calculate this linear expansion - shrinkage we can use the following formula:
∆L =∆T X L X a i.e.:
∆L = Linear expansion - shrinkage in mm
∆T = Heat variation between the operating temperature and the installation one at °C
L = Tube length in m
a= Linear expansion factor, for the aluminium it is 0,024 mm/m °C
To compensate the heat expansion / shrinkage it is advise to use few precautions:
• To fix tube please use the collars art. 90810/90820 so that the tube can easily slide
• The installation have to be positioned, considering at the two ends free space which permits the expansion - shrinkage and supports have to be fixed as showed in the above picture:
