Fault
Diagnosis
Cause
Remedy
Dosing flow too
small.
Suction valve: During the discharge
stroke, the dosing liquid flows back in-
to the suction line.
Discharge valve: During the suction
stroke, the dosing liquid flows back in-
to the dosing head.
The pump takes in less.
Suction/discharge valves dirty or leaky.
Clean or replace valves.
Dosing flow depends very much on
the pressure.
If the counter-pressure is low, the dos-
ing flow increases considerably. If the
stroke frequency rises, the dosing flow
increases excessively.
Too much clearance between piston and
slide valve, or the stroke frequency of
the pump is too low (too much slip).
Replace the piston and piston slide
valves. Use other hydraulic oil with a
higher viscosity (mainly for frequen-
cy converter operation and higher
counter-pressures).
Pressure gauge in discharge line.
Counter-pressure has seriously in-
creased. Overpressure valve is adjusted
too low.
Readjust the zero point.
Correct the setting of the pressure
relief valve.
Especially at stroke frequencies below
15 strokes/min., e.g. frequency con-
verter operation.
Degassing valve (M) is not working prop-
erly.
Replace the degassing valve (M) or,
if necessary, replace with
∅
8 ball.
Pump doses too
much.
Pressure gauge in discharge line.
Counter-pressure has seriously dropped. Readjust the zero point.
Heavy overdose.
Inlet pressure of suction line higher than
counter-pressure of discharge line.
Install a pressure-loading valve.
Overdosing at high dosing flow set-
tings and flows.
Too big dynamic in the suction line.
Install a pulsation damper on the
suction side.
Related information
8.1 Initial start-up/subsequent start-up
42
English (GB)
Summary of Contents for DMH 25X
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