Iwaki EWN-A Series Automatic Air Vent Metering Pump

The Iwaki EWN-A series is an electromagnetic metering pump with an automatic air vent mechanism built into the pump head. The air vent valve expels entrained air continuously, so gassing liquids such as sodium hypochlorite or hydrogen peroxide can be injected without gas lock and without a separate degassing step. Capacity ranges from 1.8 L/h (EWN-B11) to 6.6 L/h (EWN-C21) at a rated discharge pressure of 0.7-1.0 MPa. Mikron Proses (Üsküdar, Istanbul) supplies Iwaki pumps in Turkey and provides application consulting on pump selection.

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The EWN-A shares its electromagnetic metering pump platform with the EWN-R series and the EWN-Y series. For the wider range of Iwaki dosing pumps, see Iwaki chemical metering pumps.

Automatic air vent mechanism

An air vent valve is built into the pump chamber. Air that enters through the suction port flows through the pump head to the connection adapter. Because the discharge side is pressurized, the air travels to the automatic air vent valve, where the pressure load is lower, and leaves slowly together with a little liquid. Once the pump is free of the air lock, it returns to normal discharge. The manufacturer states that the pump resumes operation without gas lock even after a long stoppage and is capable of pumping concentrated sodium hypochlorite. A manual air vent port also allows the pressure in the discharge line to be released quickly.

Models and performance

Two drive units (B: 20 W, C: 24 W) and three effective diaphragm diameters (11: 10 mm, 16: 15 mm, 21: 20 mm) give four models: EWN-B11, EWN-B16, EWN-C16 and EWN-C21. Flow ranges from 1.8 L/h (30 mL/min) for the B11 to 6.6 L/h (110 mL/min) for the C21. The rated discharge pressure is 1.0 MPa for the B11 and C16 and 0.7 MPa for the B16 and C21. Stroke length is adjustable from 50 to 100 % on the B drive unit and from 40 to 100 % on the C drive unit, and stroke rate is adjustable from 1 to 360 strokes per minute in 1 spm steps on all models. The model code (for example EWN-B11VCERA) identifies the drive unit, the diaphragm size, the wet end material (VC or VH), the power cord (E: European) and, with the letter A, the automatic air vent type.

Wet end materials and operating conditions

The pump head and body are PVC and the diaphragm is PTFE with an EPDM layer that does not contact the liquid. The valve is alumina ceramic on type VC and Hastelloy C276 on type VH; the valve seat and O-ring are FKM on type VC and EPDM on type VH. The liquid temperature range is -10 to 40 °C, and the liquid characteristics (viscosity, freezing, slurry content) must not change during the process. The multi-voltage design accepts 100-240 VAC at 50/60 Hz; power consumption is 20 W / 0.8 A on the B drive unit and 24 W / 1.2 A on the C drive unit.