The CEH pump or so-called centrifugal combined system (combination pump) is suited with a low NPSH centrifugal impeller before the side channel stages (series connection). This NPSH inducer stage creates enough pressure to overcome the entrance pressure loss of the first side channel stage or NPSH required.
A side channel stage consist of:
• a suction intermediate piece with the suction port,
• a discharge intermediate piece with the side channel, the air displacement channel at the end of the side channel, the discharge port and the gas slot,
• a vane wheel impeller enclosed by the two intermediate pieces.
The turning of the vane wheel impeller creates an under pressure at the beginning of the side channel (centrifugal effect) and the gas or liquid with gas is drawn in. The air displacement channel provokes a positive displacement effect so the gas remaining at the root of the vane wheel impeller is forced out through the gas slot. The pressure generating is obtained by the repetitive re-entering of the liquid in the side channel (corkscrew movement).
A side channel pump can de-aerate and degas the suction line by itself and is thus very suitable for suction lift operation. A side channel pump can handle large quantities of (entrained) gas. Mixtures up to a gas share of 50% are possible. The ability for selfpriming and the handling of large amounts of (entrained) gas, will guarantee continuous operation even in case of evaporation and therefore contribute to a higher level of safety in industrial processes.
To avoid cavitation the distance between the liquid level and the entrance at the suction side of the pump is restricted. This distance is related to the NPSH or Net Positive Suction Head. The NPSH for CEH pumps is very low due to it special construction. The axial entrance and its larger diameter results in a less disturbed flow and lower friction losses. Together with the low NPSH of the centrifugal impeller the CEH can handle a positive suction head of less than 0.5 m. This makes the CEH very suitable for pumping liquids near their boiling point at reasonable economic expenses and the low NPSH guarantees also full output capacity because of operation without cavitation.