Self-priming and evacuating air
Manual or automatic
All users of diaphragm metering pumps know the problem of “air in the suction hose”. The dosing pump is running, but it just can’t “grab” the liquid on the suction side. The result is that the pump is running and running without the required amount coming out on the pressure side. Either too little chemistry is added to the process, or maybe none at all. Both have consequences and cost time and money.
The standard solution is to manually vent the pump before each start-up and after a long standstill. But it can seem a little cumbersome. Furthermore, the routine seem futile and pointless, since the problem does not occur every time – and then there is a natural risk that it will be “forgotten”.
Automatic venting, on the other hand, would solve the problem completely, and here IWAKI can help with several variants according to media and task. Here are some examples:
’High compression head’ is the simple solution:
Certain liquids emit gases to the surroundings, thus easily building up air in the suction pipe. Especially at longer standstill. An example of such a liquid is chlorine, which gases at atmospheric pressure.
For dosing chlorine, for example in swimming pools, IWAKI has developed a special pump head that compresses the sucked air and “shoots” it out on the pressure side in small quantities.
The solution is a high compression head design, where the pump body’s “dead volume” is smaller than normal. With a “high compression head” the air (gas) is automatically removed and the pump doses again in the normal way, completely without manual venting.
For more information, see
page 5 of the EWN-R brochure.
Automatic air vent valve
Higher amounts of gas can have difficult to escape without special action. To prevent this problem, IWAKI has developed an automatic air vent valve for mounting on the pressure side of the metering pump.
The automatic air vent valve allows continuous venting via a separate hose. In this way, IWAKI prevents the formation of air lock conditions that could block the fluid.
With the automatic air vent valve, the dosing runs as intended.
For more information, see page 1 in the EWN-A brochure.
Example: IX-pumps with automatic air vent
With the high compression design of the IX pumps, the air is quickly evacuated from the pump head, thus preventing the air-lock problem where the pump cannot ‘grab’ the liquid.
With a fixed (full) stroke, maximum compression is maintained, resulting in fast priming and evacuation of air at any flow or pressure.
See the IX-pumps
Watch the video
Flow control with feedback to the pump
If the dosage must proceed very accurately and without delay, then IWAKIs flow control feedback to the pump (EFS) is used.
The EFS continuously monitors the dosed amount, and if air is detected in the system, it is evacuated through the air vent valve. To achieve the set dosing volume additionally pump strokes are added automatically.
This is done with an accuracy of guaranteed +/- 5%, and in practice down to +/- 1%. Both values are unique in the market!
In the EWN-Y-A brochure you can read more about the unique “Non-Gas Lock system”, which together with IWAKI’s EFS flow control ensures an accurate dosage.
FCM flow checker
FCM is a simple flow checker mounted on the suction side of the electromagnetic metering pump and provides feedback via plc.
The FCM type detects the fluid supply on the suction side and gives the liquid supply status as a pulse. It can keep track of the number of pump strokes and detect poor supply of the liquid.