Danfoss PAH 2, Installation, Operation And Maintenance Manual

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Guideline Trouble shooting guide for PAH, PAHT, PAHT C , PAHT G pumps
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180R9379 | AQ188686503004en-000801 | PAH 2-12.5 } 07.2022
Cause Remedy Comments
2 .1 Wear on pump
Large internal leakage due to:
2 .1 .1 Dismantle the pump .
2 .1 .2 Check valve plate .
Valve plate has marks/scratches on the
surface facing the port plate . Minor wear
on valve plate can cause large internal
leakage . See Index 6 .1 .
2 .1 .3 Check port plate .
Port plate has marks/scratches on the
surface facing the valve plate . Minor wear
on port plate can cause large internal
leakage . See Index 6 .2 .
2 .1 .4 Check cylinder barrel .
Liners in cylinder barrel may be scratched
or worn . Insert a piston in the liner and
check the fit . If there is any space (clear-
ance) between liner and piston, liner or
piston is worn .
2 .1 .5 Pre-treatment:
Analyse fluid for content of particles .
- Check that filters are OK and working
correctly .
2 .1 .6 Main filtration:
Check that the correct filter type is used
(particles in fluid must not exceed 10 μm) .
Danfoss High Pressure Pumps supplies
filters, please contact the sales office .
2 .1 .7 Fluid type:
The PAH/PAH F (tapwater) and PAHT/PAHT
G (ultra pure water) pumps are designed
for water operation; for any other fluid,
please contact Danfoss High Pressure
Pumps sales office for further help .
2 .1 .8 High fluid temperature:
If fluid temperature is above 50°C, stop the
pump immediately .
- Check internal parts (see above) .
Typical signs of wear:
Polished surface all over the swash plate .
Normally, only half of the swash plate = the
pressure side is polished . See index 6 .3 .
If the ring is missing, the piston is very worn .
The filters can be bypassed, even if they are
correctly mounted . Some filters can create
channelling where particles can pass through
the filter in tunnels . String wounded filters are
typically channelling filters . A string wound filter
may have a filtration efficiency of only 50%,
which will cause internal wear and must always
be followed by a main filter .
Insufficient filtration means that too many or too
large hard particles can pass the main filter
because it is damaged, bypassed or simply too
poor . Filtration efficiency must be 99 .98%
(Beta = 5000) at 10 μm to prevent abnormal
wear of the pump .
Temperature > 50° C will cause wear on internal
pump parts . Mount a temperature switch and
check its set point / function . The temperature
switch will ensure that the pump stops at fluid
temperatures > 50° C .
2 .2 Low inlet pressure 2 .2 .1 Check that booster pump supplies the
right pressure/flow .
2 .2 .2 Check if filters require replacement .
If the pressure drop across the filters is too high,
the booster pump does not deliver sufficient
flow/pressure . No pressure or low pressure
results in cavitation and insufficient internal
lubrication causing wear on internal pump parts .
Mount a low-pressure switch in front of the
pump and check its set point/ function . The
low- pressure switch ensures that the pump does
not start until the inlet pressure has reached 1
bar .
2 .3 Rotation speed (rpm) 2 .3 .1 If VFD-operated, check frequency .
2 .3 .2 Check that rotation speed of the electric
motor is as stated on name plate on
electric motor . Check that the motor rotor
winding is not damaged .
Speeds below minimum limit (see Data sheet)
result in insufficient internal lubrication causing
wear on the internal pump parts .
2. Reduced flow/reduced pressure