Tubing & Nominal Diameter
Selection of tube size
To determine the required tube size, two parameters of the application are decisive: Volume flow or flow rate and maximum pressure.
The possible volume flow through a tube can be determined as a function of the flow rate using the following relationship:
The flow rate must be selected depending on the application and the medium. Typically, this is between 2 and 12 m/s for hydraulic and high-pressure applications.
Table 1 shows the relationship between nominal size and volume flow for the nominal sizes commonly used in the high-pressure range at the exemplary flow rate of 4 m/s, 8 m/s and 12 m/s.
| Nominal diameter [mm] | Q [l/min] (v = 4m/s) | Q [l/min] (v = 8m/s) | Q [l/min] (v = 12m/s) |
|---|---|---|---|
| 1,6 | 0,5 | 1,0 | 1,5 |
| 2,3 | 1,0 | 2,0 | 3,0 |
| 3,2 | 1,9 | 3,9 | 5,8 |
| 4,8 | 4,3 | 8,7 | 13,0 |
| 8,0 | 12,0 | 24,1 | 36,2 |
Table 1: Volume flows at different nominal diameters and flow rates
After selecting a suitable nominal diameter, the second decisive parameter for choosing the tube size is the maximum operating pressure. The permissible working pressure of a tube must be equal to or greater than the highest pressure peaks occurring during operation.
Table 2 shows the available high-pressure tube sizes for different nominal diameters along with their respective permissible nominal pressure.
It should be noted that two different material qualities are offered: standard and high-strength. High-strength tubes have higher inherent strength as well as greater corrosion resistance compared to standard tubes. However, there is a very significant price difference between the two versions. It is therefore advisable to use standard tubes wherever possible and to use high-strength tubes when a smaller outer diameter is important due to space constraints.
| Nominal diameter [mm] | Nominal pressure [bar] | Tube outer diameter | Material |
|---|---|---|---|
| 1,6 | 7000 | 1/4" | high-strength |
| 10000 | 3/8" | high-strength | |
| 2,3 | 4200 | 1/4" | standard |
| 3,2 | 3/8" | standard | |
| 4,8 | 9/16" | standard | |
| 8,0 | 2500 | standard |
Table 2: Tube sizes at different nominal diameters and operating pressures.
Selection of connection sizes
As the only provider worldwide, we offer the possibility for all tube sizes with regard to
- Thread standard (metric/inch), as well as
- Cone angle
to choose in order to optimally meet your requirements. Further information can be found in the chapter on high-pressure connections.
