Grundfos DMH 251 Installation And Operating Instructions Manual page 29

13.3 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 medium 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
Note
diaphragm breakage!
13.4 Checking the oil level
Check the oil level at least every two weeks and
Caution
add oil, if necessary.
Rod length of oil dipstick:
DMH 251-253: 27 mm.
Note
DMH 254-257: 35 mm.
Immersion depth to marking: approx. 5 mm.
13.5 Cleaning the suction and discharge valves
Warning
Wear protective clothing (gloves and goggles)
when working 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.
Fig. 33 Stainless-steel or plastic DN 8 valve, spring-loaded
as an option
Fig. 34 Plastic DN 20 valve
Stainless
1)
steel
Fig. 35 Stainless-steel or plastic DN 20 valve, spring-loaded
as an option
Plastic
2)
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