7.5 Venting the metering pump
NOTE
With an applied metering backpressure of > 0,05 MPa (0,5 bar), the use of a multifunction
valve from our product range is recommended.
Otherwise the fitted ball cock (see chapter 6.1.1 “Installation examples”, Fig. 6.1) must be
opened or the metering output must be released elsewhere.
To ensure an optimal suction performance, the stroke length should be set to 100%.
In the event that pump has no suction or insufficient suction, the correct connection must
Particular caution is required when handling chemical metering media!
Metering media may escape which may cause skin irritation, depending on their properties.
Therefore, before venting, always observe the product datasheet of the metering medium to
prevent any type of injury!
It is only possible to modify the stroke length setting when the pump is running.
When using a multifunction valve (see accessory range) for the venting, use the
appropriate operating instructions.
When using a ball cock (or another venting device), place a suitable collection vessel
below the venting pipe.
Open the ball cock or relieve pump on pressure side.
Switch on the device.
Set stroke adjustment knob to 100 %
Wait until medium exits metering line free of bubbles.
Close the ball cock (if available/used).
If no metering medium enters the metering pipe, repeat the venting.
Improved suction can be achieved, if the pressure line is subsequently unscrewed and the
pump head filled with a suitable liquid.
7.6 Metering capacity calculation (volumetric measurement)
The specified metering capacities in metering pumps are always determined under ideal
conditions (metering of water at 20 °C, short suction and metering pipes, rated back-
pressure, no pressure-boosting valves in the metering line).
As these conditions never occur in practice, you are advised to determine the actual
metering rate of the metering pump under prevailing local conditions (volumetric
measurement).
Connect pump ready for operation on delivery
side (operation-specific pipe length incl. all
pressure-maintenance valves, injection valves
etc. connected during normal operation)
Set the pump to the required metering rate
(see section
7.2).
Fill a suitable measuring cylinder with the product
to be metered and insert a suction pipe.
Run the pump for exactly 1 minute and measure
the quantity sucked out of the measuring cylinder.
The value calculated in l multiplied by 60 equals the
actual metering rate in l/h.
NOTE
The volume of the measuring cylinder should be 1/50 of the required metering pump rate
in litres/h.
During volumetric measurement, the position of the suction tube may not be changed.
The determined metering rate is only valid for the stroke length currently set.
Once the stroke length setting has been adjusted, the changed metering rate must be
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