Maintenance; General Notes; Diaphragm Leakage Control For Diaphragm Leakage Detection; Cleaning And Maintenance Intervals - Grundfos DMH 25X Installation And Operating Instructions Manual

10. Maintenance

10.1 General notes

Warning
When dosing dangerous media, observe the correspond-
ing safety precautions!
Wear protective clothing (gloves and goggles) when work-
ing on the dosing head, connections or lines!
The pump housing must only be opened by personnel au-
thorised by Grundfos!
Repairs must only be carried out by authorised and quali-
fied personnel!
Switch off the pump and disconnect it from the power sup-
ply before carrying out maintenance work and repairs!
Before removing the dosing head, valves and lines, empty
any remaining medium in the dosing head into a drip tray
by carefully unscrewing the suction valve.
Observe the flow direction of valves (indicated by an ar-
row on the valve)!
Caution
Only tighten plastic valves by hand.
10.2 Diaphragm leakage control for diaphragm leakage
detection
If a diaphragm leakage has been detected, first of all check whether
an error has been displayed, as different external factors such as
the heating of dosing or hydraulic medium can cause the cracked
medium between the diaphragms to be displaced into the valve,
thereby causing an error to occur.
Checks after a diaphragm leakage detection:
1. Briefly open the deaeration screw (2u) and then close it again.
2. Switch on the pump.
3. If, after a short period of time, a diaphragm leakage is detected
again, a diaphragm has broken.
After a diaphragm breakage, replace the diaphragms and
clean the non-return valve, see section Replacing the dia-
Caution
phragm for dosing head with double diaphragm.
S
U
2u
T
1u
Dosing head with double diaphragm
Pos. Components
S Contact pressure gauge
T Ball non-return valve
U Connection piece
1u Filling screw
2u Deaeration screw
Related information
10.7 Replacing the diaphragm for dosing head with double
diaphragm

10.3 Cleaning and maintenance intervals

Checking the oil level

• Check the oil level every two weeks and add oil, if necessary.
Cleaning the valves
• At least every 12 months or after 4,000 operating hours.
• If the pump does not perform.
• In the event of a fault.
Clean the valves and replace, if necessary (for stainless-steel
valves: inner valve parts).
Changing diaphragms and gear oil
• At least every 12 months or after 8,000 operating hours, change
the dosing diaphragm and gear oil.
• In dusty installation sites, change the gear oil every 3,000
operating hours.
Cleaning the ball non-return valve of the double diaphragm
• After a diaphragm breakage, remove the ball non-return valve
immediately and clean it.
Only clean the ball non-return valve after a diaphragm
Note
breakage!
10.4 Checking the oil level
Check the oil level at least every two weeks and add oil, if
Caution
necessary.
Rod length of oil dipstick:
DMH 251-253: 27 mm.
Note
DMH 254-257: 35 mm.
Immersion depth to marking: approx. 5 mm.

10.5 Cleaning the suction and discharge valves

Warning
Wear protective clothing (gloves and goggles) when work-
ing on the dosing head, connections or lines!
Before removing the dosing head, valves and lines, empty
any remaining medium in the dosing head into a drip tray
by carefully unscrewing the suction valve.
DN 8 valve
• Screwed connection 5/8"
• Stainless steel or plastic
• Spring-loaded (optional).
DN 20 valve (valve for suction side only), with adapter
• Screwed connection 1 1/4"
• Plastic.
DN 20 valve
• Screwed connection 1 1/4"
• Stainless steel or plastic
• Spring-loaded (optional).
DN 32 valve (for 60 Hz operation, suction side only), with
adapter
• Flange connection
• Stainless steel or plastic.
Clean the suction and discharge valves as follows:
1. Unscrew the valves.
2. Unscrew the screw parts and valve set using round pliers.
3. Dismantle the inner part (seat, O-ring, balls, ball cages and, if
present, spring).
4. Clean all parts. Replace faulty parts by new ones.
5. Re-assemble the valve.
6. Replace the O-rings by new ones. Refit the valve.
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