English (GB)
34
11. Fault finding chart
Warning
Actions that are taken to correct faults on the pump
and that are not described in this manual, must only
be carried out by personnel authorised by Grundfos!
Fault
Diagnosis
Cause
Remedy
No dosing flow
even at a low
counter-pressure.
(Pump is running
without any noise).
No motor sound or vibrations.
Fan is not rotating.
Motor is not running.
Connect the power supply or
replace the motor, if blown.
When the oil-filling screw (F) is
removed, use the dipstick to observe
a calm oil surface. There is no
"sloshing".
Motor runs, but the eccentric shaft is
not rotating. No piston movement.
Spiral pin or motor shaft broken.
Remove the motor and eccentric
shaft. Replace damaged parts.
Oil level too low. See oil dipstick (F).
No reaction of the overpressure
valve if the suction line is closed.
Not enough oil in the pump.
Air is penetrating the piston flange
through the control holes.
Fill in oil. Deaerate the pump, see
section
No dosing flow on the discharge
side.
Dosing head is not filled. Suction line
empty. Tank empty.
Deaerate the dosing head.
Fill/exchange the tank on the
suction side.
No dosing flow
even at a low
counter-pressure.
(Pump is running
noisily although the
overpressure valve
reacted).
The overpressure valve reacts
independently of the dosing flow
adjustment (10 % to 100 %).
Valve on discharge side closed.
Open the valve.
Counter-pressure is higher than the
adjusted pressure at the overpressure
valve.
Adjust the overpressure valve
higher, but only if the pump is
designed for this. Never block the
overpressure valve.
Discharge valve is installed in the
opposite direction of the flow. Observe
the arrow on the valve.
Install the discharge valve
correctly.
The diaphragm protection system
(AMS) responds.
The overpressure valve reacts
independently of the dosing flow
adjustment (10 % to 100 %).
Valve on suction side closed.
Open the valve.
Suction filter obstructed.
Clean the suction filter.
Replace, if necessary.
Suction valve jammed (does not open).
Dismantle and check the suction
valve.
Suction valve has a too strong spring.
Use the fitting spring, or use
double ball valve for checking.
Suction valve is installed in the
opposite direction of the flow.
Observe the arrow on the valve.
Install the suction valve correctly.
The diaphragm protection system
(AMS) responds.
The overpressure valve reacts at
100 % dosing flow.
When reducing the flow ~10 % to 20
%, the overpressure valve does not
react any more.
Dosing head is not completely
deaerated.
Fill the dosing head completely.
Pump is cavitating (dosing liquid with
too high viscosity; dosing liquid with
too high steam pressure at operating
temperature = degassing of the liquid;
suction lift too high; wrong design of
the system on suction side).
Use a gear with a low stroke
number; use valves with bigger
nominal width; realise positive inlet
pressure.
Diaphragm broken (not enough oil in
the enclosure of the pump; piston
flange).
Clean and grease well all parts
using oil according to regulations.
Then install a new diaphragm.
Pump does not
dose or pressure
relief valve opens.
Discharge valve of pump is clogged or
ball guide in the valve is worn due to
corrosive or abrasive media.
Uninstall the discharge valve.
Dismantle and clean, or if the bars
of the ball guide are worn, replace
the valve.
