Impeller
- TN - Forward-curved impellers are made of galvanised steel, designed for high circumferential speed. The inlet cones are manufactured from galvanised steel or glass fibre reinforced polyamide.
- HN - Backward-curved impellers are made of seawater proof aluminium. Their low mass moment of inertia allows to reduce motor sizes. The inlet cones are made of galvanised steel. All fan impellers are statically and dynamically balanced in two plains to quality level G 2.5 (DIN ISO 1940).
Speed Control
Electronic and transformer-type controllers are available. Corresponding controllers are listed below each fan curve. For controller details, please refer to chapter 7 of this catalogue (p.332ff.).
Fan Performance Curves
The performance curves for these fan types have been established in mounting position B (installed on the pressure side with free inlet) and represent the total pressure increase
Δ pt as a function of the volume flow. The dynamic pressure pd2 refers to the flange cross-sectional area of the fan outlet.
Sound Levels
The ascertaining of the sound data follows the enveloping surface method according to DIN 45 635 section 38, or the channel technique as defined in DIN 45 635, section 9. The figures given in the fan performance curves are the A-weighted sound power levels LWA4 (in decibels) on the outlet side in a ducted system. The A-weighted sound power level at the inlet side LWA5 according to DIN 45 635, part 38 is obtained as follows: LWA5 = LWA4 - 3 dB(A)
The octave sound power level is important for the choice of suitable sound attenuators. It is calculated as follows. LWAOkt = LWA4 - LWArel
The relative octave sound power level LWArel at octave medium frequency can be taken from the tables below each fan curve. These levels have been established at 0.5 x Vmax.
The A-weighted sound pressure level LPA at a distance of 1 metre is obtained approximately by deducting 7 dB(A) from the A-weighted sound power level LWA.
It is important to note that reflexion and environmental characteristics as well as resonant frequencies influence the sound pressure levels in different ways.