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