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6.5 Possible Failures
Failure
Dosing pump does not run
Dosing pump does not suck in
Dosing pump does not dose
Dosing output of the pump
inaccurate
24
Cause
Not connected to mains
Wrong mains voltage
Electrical failure
The diaphragm breakage indication has
responded.
Leaky suction line
Cross-section of the suction line too narrow
or or suction line too long
Clogged suction line
Foot valve covered by sediment
Crystalline deposits in the valves
Diaphragm broken or diaphragm tappet torn
out
Dosing tank is empty
Air in the suction line and dosing head
Medium too viscous or density too high
Crystalline deposits in the valves
Valves not correctly assembled
Injection point blocked
Inexpert installation of lines and peripheral
equipment
Dosing head not fully deaerated
Degassing medium
Valves partially soiled or incrusted
Fluctuations of back pressure
Fluctuations of suction height
Siphon effect (admission pressure higher
than back pressure)
Leaky or porous suction line or pressure line Replace the suction line or pressure line
Parts in contact with media not resistant
Dosing diaphragm worn out (incipient tears)
Variation of the dosing medium (density,
viscosity)
Correction
Connect the mains line
Replace the dosing pump
Return the dosing pump to the works for
repair
Replace the diaphragm.
Exchange or seal the suction line
Check with specification of Grundfos
Rinse or replace the suction line
Suspend the suction line at a higher position
Clean the valves
Exchange the diaphragm
Change the tank
Wait, until the pump has deaerated
Check the installation
Clean the valves
Assemble the valve inside parts in the right
order and check or possibly correct the flow
direction
Check and possibly correct the flow direction,
or remove the occlusion
Check for perviousness and correct
installation
Repeat deaeration
Check the installation
Clean the valves
Application of a pressure retention valve and a
pulsation damper
Keep the suction level constant
Install a pressure retention valve
Replace with resistant materials
Replace the diaphragm, also observe
maintenance instructions
Examine the concentration, possibly employ
an agitator
DMX model 227
15.720023-V3.0
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