Danfoss DDC20, DDC24 Service guide
Service Manual
Axial Piston Pumps
DDC20/24
www.danfoss.com
Service Manual
DDC20/24 Axial Piston Pumps
Revision history Table of revisions
Date Changed Rev
August 2019 Added DDC24 0401
August 2017 change charge pump housing 0302
March 2015 add implement pump option CA
March 2014 Danfoss layout BA
September 2011 First printing AA
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Service Manual
DDC20/24 Axial Piston Pumps
Contents
Introduction
Overview..............................................................................................................................................................................................4
Warranty.............................................................................................................................................................................................. 4
General instructions........................................................................................................................................................................ 4
Remove the unit.......................................................................................................................................................................... 4
Keep it clean..................................................................................................................................................................................4
Lubricate moving parts.............................................................................................................................................................4
Replace all O-rings and gaskets............................................................................................................................................. 4
Secure the unit.............................................................................................................................................................................5
Safety Precautions............................................................................................................................................................................5
Unintended machine movement..........................................................................................................................................5
Flammable cleaning solvents.................................................................................................................................................5
Fluid under pressure..................................................................................................................................................................5
Personal safety............................................................................................................................................................................. 5
Gauge port locations and installation
Gauge port locations and sizes- with Aux pad...................................................................................................................... 6
Gauge port locations and sizes- with Gerotor....................................................................................................................... 7
Gauge port locations and sizes- with Implement pump....................................................................................................8
Adjustments
Pump adjustment.............................................................................................................................................................................9
Standard Procedures.......................................................................................................................................................................9
Charge pressure relief valve......................................................................................................................................................... 9
High pressure relief valve............................................................................................................................................................10
Loop flushing valve.......................................................................................................................................................................11
Troubleshooting
Troubleshooting overview......................................................................................................................................................... 12
System operating hot...................................................................................................................................................................12
Transmission operating normally in one direction only..................................................................................................12
System noise or vibration........................................................................................................................................................... 12
System will not operate in either direction.......................................................................................................................... 12
Sluggish system response...........................................................................................................................................................13
Minor repair
Charge pump...................................................................................................................................................................................14
Implement pump...........................................................................................................................................................................16
Shaft and shaft seal....................................................................................................................................................................... 17
High pressure relief valve (HPRV).............................................................................................................................................21
Charge pressure relief valve (CPRV)........................................................................................................................................ 22
Loop flushing valve.......................................................................................................................................................................23
Bypass valve.....................................................................................................................................................................................24
Optional coupling..........................................................................................................................................................................25
Torque charts
Charge pump fastener and torque chart.............................................................................................................................. 26
Implement pump fasteners and torque chart.....................................................................................................................26
Gerotor plugs and torque........................................................................................................................................................... 27
Auxiliary pad plug sizes and torque chart.............................................................................................................................28
Implement pump plug sizes and torque chart................................................................................................................... 29
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Service Manual
DDC20/24 Axial Piston Pumps
Introduction
Pump service overview
This manual includes information on maintenance, troubleshooting, and minor repair of DDC20/24
pumps.
Performing minor repairs may require removal from the vehicle/machine. Thoroughly clean the unit
before beginning maintenance or repair activities. Since dirt and contamination are the greatest enemies
of any type of hydraulic equipment, follow cleanliness requirements strictly. This is especially important
when changing the system filter and when removing hoses or plumbing.
A worldwide Global Service Partner Network is available for major repairs. Major repairs require the
removal of the unit’s endcap, which voids the warranty unless done by a Global Service Partner. Danfoss
Global Service Partners are trained by the factory and certified on a regular basis. You can locate your
nearest Global Service Partner using the distributor locator at www.danfoss.com.
For detailed technical information, refer to the Technical Information manual.
Warranty
Performing maintenance, and minor repairs according to the procedures in this manual will not affect
your warranty. Major repairs requiring the removal of the units endcap voids the warranty unless
completed by a Danfoss Global Service Partner.
General instructions
Remove the unit
Prior to performing major repairs, remove the unit from the vehicle/machine. Chock the wheels on the
vehicle or lock the mechanism to inhibit movement. Be aware that hydraulic fluid may be under high
pressure and/or hot. Inspect the outside of the pump and fittings for damage. Cap hoses and plug ports
after removal to prevent contamination.
Keep it clean
Cleanliness is a primary means of assuring satisfactory pump life, on either new or repaired units. Clean
the outside of the pump thoroughly before disassembly. Take care to avoid contamination of the system
ports. Cleaning parts using a clean solvent wash and air drying is usually adequate.
As with any precision equipment, keep all parts free of foreign materials and chemicals. Protect all
exposed sealing surfaces and open cavities from damage and foreign material. If left unattended, cover
the pump with a protective layer of plastic.
Lubricate moving parts
During assembly, coat all moving parts with clean hydraulic fluid. This assures that these parts are
lubricated during start-up.
Replace all O-rings and gaskets
Danfoss recommends you replace all O-rings, seals, and gaskets during repair.Lightly lubricate all O-rings
with clean petroleum jelly prior to assembly. Grease must be soluable in hydraulic fluid.
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DDC20/24 Axial Piston Pumps
Introduction
Secure the unit
For major repair, place the unit in a stable position with the shaft pointing downward. It is necessary to
secure the pump while removing and torquing components and fasteners.
Safety Precautions
Always consider safety precautions before beginning a service procedure. Protect yourself and others
from injury. Take the following general precautions whenever servicing a hydraulic system.
Unintended machine movement
Unintended movement of the machine or mechanism may cause injury to the technician or bystanders.
To protect against unintended movement, secure the machine or disable/disconnect the mechanism
while servicing.
Warning
Flammable cleaning solvents
Warning
Some cleaning solvents are flammable. To avoid possible fire, do not use cleaning solvents in an area
where a source of ignition may be present.
Fluid under pressure
Warning
Escaping hydraulic fluid under pressure can have sufficient force to penetrate your skin causing serious
injury and/or infection. This fluid may also be hot enough to cause burns. Use caution when dealing with
hydraulic fluid under pressure. Relieve pressure in the system before removing hoses, fittings, gauges, or
components. Never use your hand or any other body part to check for leaks in a pressurized line. Seek
medical attention immediately if you are cut by hydraulic fluid.
Personal safety
Warning
Protect yourself from injury. Use proper safety equipment, including safety glasses, at all times.
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System port A
System port B
O-ring plug 9/16-18UNF-2B
L3 Case Drain
O-ring Plug 3/4-16UNF-2B
M3 Charge gauge / E - Charge inlet
O-ring plug 9/16-18UNF-2B
MA system pressure gauge port
O-ring plug 9/16-18UNF-2B
MB system pressure gauge port
O-ring plug 9/16-18UNF-2B
L1 Case Drain
O-ring Plug 3/4-16UNF-2B
L2 Case Drain
O-ring Plug 3/4-16UNF-2B
M3 Charge gauge / E - Charge inlet
Service Manual
DDC20/24 Axial Piston Pumps
Gauge port locations and installation
DDC20/24 gauge port locations and sizes- with Aux pad
The following drawing and table show the gauge port locations and gauge sizes needed.
DDC20/24 with aux pad
Port Information
Port Identifier Port Size Wrench Size Pressure Obtained Gauge Size, bar [psi]
L1/L2/L3 3/4-16 UNF 5/16 inch internal hex Case Drain 10 [100]
MA/MB 9/16-18 UNF 11/16 hex wrench System Pressure 500 [5000]
M3/E 9/16-18 UNF 1/4 inch internal hex Charge Pressure 50 [1000]
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S -Charge
suction port
MA
system pressure gage port
O-ring plug 9/16-18UNF-2B
L3 Case Drain
O-ring Plug 3/4-16UNF-2B
M3 Charge Pressure Gauge Port
O-ring Plug 7/16-20UNF-2B
L1 Case Drain
O-ring Plug 3/4-16UNF-2B
MB
system pressure gage port
O-ring plug 9/16-18UNF-2B
Service Manual
DDC20/24 Axial Piston Pumps
Gauge port locations and installation
DDC20/24 gauge port locations and sizes- with Gerotor
The following drawing and table show the gauge port locations and gauge sizes needed.
DDC20/24 with gerotor
Port Information
Port Identifier Port Size Wrench Size Pressure Obtained Gauge Size, bar [psi]
L1/L2/L3 3/4-16 UNF 5/16 inch internal hex Case Drain 10 [100]
MA/MB 9/16-18 UNF 11/16 hex wrench System Pressure 500 [5000]
S 7/8-14 UNF N/A (plastic shipping plug) Charge Inlet 2 [30] Vacuum
M3 7/16-20 UNF 3/16 inch internal hex Charge Pressure 50 [1000]
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S -Charge
suction port
M3 Charge Pressure Gauge Port
O-ring Plug 9/16-18UNF-2B
L3 Case Drain
O-ring Plug 3/4-16UNF-2B
L1 Case Drain
O-ring Plug 3/4-16UNF-2B
MA system pressure gage port
O-ring plug 9/16-18UNF-2B
MB system pressure gage port
O-ring plug 9/16-18UNF-2B
A System Port
B System Port
L2 Case Drain Port
O-ring plug 3/4-16UNF-2B
D Implement Discharge
O-ring plug 9/16-18UNF-2B
M3 Charge Gauge/
O-ring plug 9/16-18UNF
E Implement Return
E Implement Return
Service Manual
DDC20/24 Axial Piston Pumps
Gauge port locations and installation
DDC20/24 gauge port locations and sizes- with implement pump
The following drawing and table show the gauge port locations and gauge sizes needed.
DDC20/24 with implement pump
Port Information
Port Identifier Port Size Wrench Size Pressure Obtained Gauge Size, bar [psi]
L1/L2/L3 3/4-16 UNF 5/16 inch internal hex Case Drain 10 [100]
MA/MB 9/16-18 UNF 11/16 hex wrench System Pressure 500 [5000]
S 7/8-14 UNF N/A (plastic shipping
D 9/16-18 UNF 1/4 inch internal hex Implement Pressure 100 [2000]
M3/E 9/16-18 UNF 1/4 inch internal hex Charge Pressure 50 [1000]
plug)
Charge Inlet 2 [30] Vacuum
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Service Manual
DDC20/24 Axial Piston Pumps
Adjustments
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
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.
Caution
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
contamination. Refer to the Torque charts 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.
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