Fault Finding Chart; Maintenance; General Notes; Cleaning And Maintenance Intervals - Grundfos DMX 221 Installation And Operating Instructions Manual

10.6 Fault finding chart

Fault Cause
Discharge line
blocked.
Permanent
output from
Relief valve incorrectly
the relief
set (too low).
valve.
Diaphragm faulty.
Relief valve dirty.

11. Maintenance

11.1 General notes

Warning
When dosing dangerous media, observe the
corresponding safety precautions!
Risk of chemical burns!
Wear protective clothing (gloves and goggles)
when working on the dosing head, connections
or lines!
Do not allow any chemicals to leak from the
pump. Collect and dispose of all chemicals
correctly!
Warning
The pump housing must only be opened by
personnel authorised by Grundfos!
Repairs must only be carried out by authorised
and qualified personnel!
Switch off the pump and disconnect it from the
power supply before carrying out maintenance
work and repairs!
For transport or cleaning, the venting cartridge
must be closed.
Caution
Before start-up, open the venting cartridge
(pull cap approx. 5 mm).

11.2 Cleaning and maintenance intervals

In the event of a diaphragm leakage, the dosing
liquid may leak out of the hole in the intermediate
flange between the pump and the dosing head.
The parts inside the housing are protected from
the dosing liquid for a short time (depending on
Caution
the type of liquid) by the housing sealing. It is
necessary to check regularly (daily) if liquid is
leaking out of the intermediate flange.
For maximum safety, we recommend the pump
version with diaphragm leakage detection.
11.2.1 Changing the gear grease
Warning
The gear grease must only be changed by
authorised and qualified personnel.
For this purpose, send the pump to Grundfos or
an authorised service workshop.
To ensure trouble-free operation, it is recommended to have the
gear grease changed after five years or after 20000 operating
hours.
11.2.2 Cleaning the diaphragm and valves
Clean the diaphragm and valves, and replace if necessary
(with stainless-steel valves: inner valve parts):
• At least every 12 months or after 4000 operating hours.
When operating with a counterpressure of 16 bar, every six
months or after 2000 operating hours.
• In the event of a fault.

11.3 Cleaning the suction and discharge valves

Remedy
Check and possibly
If the pump loses capacity, clean the suction and discharge
correct the
valves as follows:
discharge-side dosing
1. Unscrew the valve.
system.
Set the relief valve to a
higher opening
pressure.
Replace the
diaphragm.
2. Clean all parts. Replace faulty parts by new ones.
Clean the relief valve.
3. Re-assemble the valve.
4. Replace the O-rings by new ones. Refit the valve.

11.4 Maintenance of the relief valve

11.4.1 Cleaning and maintenance intervals
Clean the relief valve, and replace the diaphragm, if necessary.
•
•
11.4.2 Replacing the diaphragm of the relief valve
1. Switch off the pump and disconnect it from the power supply.
2. Make it impossible for a return flow or overpressure to occur.
3. Loosen the four screws on the top part of the relief valve.
4. Remove the top part of the relief valve.
5. Remove the diaphragm.
6. Insert a new diaphragm.
7. Refit the top part of the relief valve and cross-tighten the
8. Start up the dosing system.
9. Tighten the screws on the top part of the relief valve after
If possible, rinse the dosing head, e.g. by
Caution
supplying it with water.
– DN 20
Unscrew the screw part resp. valve seat with round pliers.
– DN 8
Press out the valve cartridge and remove the valve seat
from the ball cage.
Observe the direction arrow on the valve.
DN 8
*
Fig. 26 Stainless-steel or plastic valve DN 8 / DN 20,
* spring-loaded as an option
The O-rings must be correctly placed in the
specified groove.
Caution
Observe the flow direction (indicated by an arrow
on the valve)!
At least every 12 months or after 8000 operating hours.
In the event of a fault.
screws.
Maximum torque: 6 Nm.
48 operating hours.
Maximum torque: 6 Nm.
DN 20
*
*
21