Replacing The Diaphragm - Grundfos DMX 221 Installation And Operating Instructions Manual

11.5 Replacing the diaphragm

Adjust the stroke length only while the pump is
Caution
running!
For transport or cleaning, the venting cartridge
Caution
must be closed.
If possible, rinse the dosing head, e.g. by
Note
supplying it with water.
11.5.1 Switching off the pump
1. While the pump is running, set the stroke-length adjustment
knob to 100 %.
2. Switch off the pump and disconnect it from the power supply.
3. Depressurise the system.
4. Take suitable steps to ensure that the returning dosing
medium is safely collected.
11.5.2 Replacing the diaphragm
1. Loosen the six dosing head screws.
2. Remove the dosing head.
3. Turn the fan blades until the diaphragm reaches the front
dead centre (the diaphragm detaches itself from the
diaphragm flange).
4. Unscrew the diaphragm by manually turning it
counter-clockwise.
5. Check the parts and replace by new ones, if necessary.
6. Screw in the new diaphragm completely. Then turn it back
until the holes in the diaphragm and the flange coincide.
7. Turn the fan blades until the diaphragm reaches the bottom
dead centre (the diaphragm is pulled onto the diaphragm
flange).
8. Refit the dosing head carefully and cross-tighten the screws.
Maximum torque: 6 Nm.
9. Deaerate and start the dosing pump.
Before start-up, open the venting cartridge (pull
Caution
cap approx. 5 mm).
After initial start-up and after each time the
diaphragm is changed, tighten the dosing head
screws.
Caution
After approximately 6-10 operating hours or two
days, cross-tighten the dosing head screws
using a torque wrench.
Maximum torque: 6 Nm.
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