Pump adjustment
This section offers instruction on adjustment of pump components. Read through the entire topic before
beginning a service activity. Refer to
Gauge port locations and installation
for location of gauge ports and
suggested gauge size.
Standard Procedures
C
Caution
Contamination can damage internal components and void the manufacturer’s warranty. Take
precautions to ensure system cleanliness when removing and reinstalling system lines
1. With the prime mover off, thoroughly clean the outside of the pump.
2. If removing the pump from the machine, tag each hydraulic line connected to the pump. If hydraulic
lines are disconnected, plug each open port, to ensure that dirt and contamination do not get into
the pump.
3. Ensure the surrounding areas of the machine are clean and free of contaminants such as dirt and
grime.
4. Look at the hydraulic fluid for signs of system contamination, oil discoloration, foam in the oil, sludge,
or small metal particles.
5. If there are signs of contamination in the hydraulic fluid, drain the hydraulic system, replace all filters,
flush the lines and fill the system with the proper hydraulic fluid.
DDC20/24 charge pressure relief valve adjustment
The following procedure explains how to check for proper operation of the charge pressure relief valve.
Charge pressure is the measured pressure minus case drain pressure.
1. Install a 50 bar [1000 psi] pressure gauge at the charge pressure gauge port. Install a 10 bar [100 psi]
gauge at one of the case pressure ports. Operate the system with the pump in neutral (zero
displacement) when measuring charge pressure.
Pressure listed in model code assumes a charge flow of 15 l/min [4 US gal/min], and are referenced to
case pressure. At higher charge flows, the charge pressure will rise over the rated setting.
2. The table shows the acceptable pump charge pressure range for some nominal charge relief valve
settings (refer to model code located on serial number plate).
3. If measured pressure is not correct, disassemble the valve and look for signs of wear or
chapter for wrench sizes and torque settings.
4. If the valve is worn, replace the entire valve assembly.
5. Re-check the charge pressure setting.
Service Manual
DDC20/24 Axial Piston Pumps
Adjustments
©
Danfoss | August 2019
L1120413 | AX00000135en-000401 | 9
