Troubleshooting
Type of fault
37
Subject to technical changes.
Stepper motor-driven diaphragm dosing pump NXP-M and NXP-P
Operating instructions
Possible cause
Remedy
Viscosity too high.
è
Possibly reduce the concentration
of the dosing medium or increase
the temperature.
è
Install spring-loaded valves.
è
Increase the pipe diameter.
Current supply interrupted.
è
Reconnect the current supply.
Dry the valves.
è
Dampen the dosing head and the
valves
è
Vent the dosing head.
Air in the suction line with
simultaneous pressure on the
discharge valve.
è
Vent the dosing head or the lines.
Table 31: Type of fault: Dosing pump does not prime
13.1.4 Delivery rate varies
Possible cause
Remedy
Valve leaking or blocked.
è
Clean the valve and vent the
dosing pump.
è
Tighten the screw connections.
Valve damaged (e.g. valve
balls).
è
Remove the damaged parts or
install a new valve.
Suction line is leaking.
è
Seal the leak locations or replace
the parts.
Suction line is blocked (e.g.
screen in foot valve).
è
Clean the suction line.
Viscosity too high.
è
Possibly reduce the concentration
of the dosing medium or increase
the temperature.
è
Install spring-loaded valves.
è
Increase the pipe diameter.
The dosing pump's electrical
data does not match that of
the mains supply.
è
Check the electrical installation.
Suction side pressure too high
(pump siphoning).
è
Install a back-pressure valve in
the pressure line.
Pressure peaks due to
acceleration with long suction
lines.
è
Install a suction pressure
regulator.
Table 32: Type of fault: Delivery rate varies
Possible cause
Remedy
Imprecise dosing due to
changeable positive and
negative suction heads.
è
Install a suction pressure
regulator.
System backpressure too
high (measured at discharge
connection of dosing pump).
è
Clean blocked injection nozzle.
è
Install pulsation dampeners to
reduce pressure peaks if pipes
are too long.
è
Check function of safety valves.
Table 32: Type of fault: Delivery rate varies
13.1.5 No stroke movement observed
Possible cause
Remedy
Diaphragm return spring
broken.
è
Contact the manufacturer.
Current supply interrupted.
è
Reconnect the current supply.
The dosing pump's electrical
data does not match that of
the mains supply.
è
Check the electrical installation.
Pressure peaks due to
acceleration with long suction
lines.
è
Install a suction pressure
regulator.
System backpressure too
high (measured at discharge
connection of dosing pump).
è
Clean blocked injection nozzle.
è
Install pulsation dampeners to
reduce pressure peaks if pipes
are too long.
è
Check function of safety valves.
Table 33: Type of fault: No stroke movement observed
13.1.6 Dosing pump delivery rate too high
Possible cause
Remedy
Suction side pressure too high
(pump siphoning).
è
Install a back-pressure valve in
the pressure line.
Pressure peaks due to
acceleration with long suction
lines.
è
Install a suction pressure
regulator.
Table 34: Type of fault: Dosing pump delivery rate too high