Troubleshooting; Troubleshooting Overview; System Operating Hot; Transmission Operating Normally In One Direction Only - Danfoss DDC20 Service Manual

Service Manual
DDC20/24 Axial Piston Pumps

Troubleshooting

Troubleshooting overview

DDC20/24 system operating hot
Cause Problem
Oil level in reservoir. Insufficient hydraulic fluid will not meet cooling demands of
system.
Heat exchanger. Heat exchanger not sufficiently cooling the system.
Charge pressure. Low charge pressure will overwork system.
Charge pump inlet High inlet vacuum will overwork system. A dirty filter will
vacuum. increase the inlet vacuum. Inadequate line size will restrict flow.
System relief If the system relief valves are worn, contaminated, or valve
pressure settings. settings are too low, the relief valves will be overworked.
System pressure. Frequent or long term operation over system relief setting will
create heat in system
DDC20/24 transmission operating normally in one direction only
Cause Problem
Control linkage Control linkage operating improperly
High pressure relief Malfunctioning HPRV can affect one direction while the other
valve functions normally.
DDC20/24 system noise or vibration
Cause Problem
Oil level in reservoir Low oil level leads to cavitation.
Aeration of the oil/ Air in system decreases efficiency of units and controls. Air in
pump inlet vacuum system is indicated by excessive noise in pump, foaming in oil,
and hot oil.
Cold oil If oil is cold, it may be too viscous for proper function and cause
cavitation
Pump inlet vacuum High inlet vacuum causes noise/cavitation.
Shaft couplings A loose shaft coupling will cause excessive noise.
Shaft alignment Misaligned shafts creates noise
Charge/High Unusual noise may indicate sticking valves. Possible
pressure relief contamination.
valves
DDC20/24 system will not operate in either direction
Cause Problem
Oil level in reservoir Low oil level leads to cavitation.
Open bypass valve If bypass valve is open, the system loop will be depressurized.
12 | © Danfoss | August 2019
This section serves as a guide for identifying and resolving undesirable system conditions.
Please observe the safety concerns listed in
equipment when resolving system issues.
Safety Precautions and the precautions related to relevant
Solution
Fill reservoir to proper level.
Check air flow and input air temperature for heat exchanger.
Clean, repair or replace heat exchanger.
Measure charge pressure. Inspect and/or replace charge relief
valve. Inspect charge pump. Repair or replace charge pump.
Check charge inlet vacuum. If high, inspect inlet filter and
replace as necessary. Check for adequate line size, length or
other restrictions
Verify settings of high pressure relief valves and replace valves
as necessary.
Measure system pressure. If pressure is too high, reduce loads.
Solution
Repair/replace control linkage
Exchange the high pressure relief valves. If the problem
changes direction, replace the valve that does not operate
correctly. Settings may be different for forward/reverse.
Solution
Fill reservoir.
Find location where air is entering into the system and fix.
Check that inlet line is not restricted and is proper size.
Allow the oil to warm up to its normal operating temperature
with engine at idle speed.
Check that inlet line is not restricted and is proper size. Check
filter and bypass valves (if present).
Replace loose shaft coupling.
Align shafts.
Clean/replace valves and test pump. May be a normal
condition.
Solution
Fill reservoir.
Close bypass valve.
L1120413 | AX00000135en-000401