With these arrangements, the motor sits in a tunnel which is isolated from air stream. This tunnel passes all the way through casing, which allows unrestricted air movement for motor cooling. This is of particular importance for higher temperature applications. The impellor is mounted onto a precision machined extension shaft, which in turn is mounted onto the motor shaft. Shaft seals are fitted to prevent ingress of dust and minimise air leakage into the motor tunnel. These seals are not gas tight and can be affected by condensation, corrosive chemicals or abrasive materials. Please refer to RHF if special seals are required.
This particular fan consists of a cylindrical casing, which is less expensive than the HD type. The flow losses encountered with this design are naturally higher than those experienced with the HD type, due to greater restriction of free area. Notwithstanding the restriction, good performance can be achieved with a small penalty on absorbed power.
Ancillaries such as spigot flanges, inlet bellmouths, casing feet and flexible connections are also available. RHF can offer non standard arrangements/special fans.