Danfoss DDC Axial Piston Pumps Size 20/24 User guide
Technical Information
DDC Axial Piston Pumps
Size 20/24
www.danfoss.com
Technical Information
DDC Axial Piston Pumps Size 20/24
Revision history Table of revisions
Date Changed Rev
February 2022 Added Option: Detent 0309
December 2021 Minor fix on Design Specifications 0308
November 2021 Added notes at Diagrams and LFV. 0307
October 2021 Added table on CPRV 0306
September 2021 Added to CPRV and Model Code: L. 0305
March 2021 Minor update in Input Shafts AB, BB, DB 0304
January 2021 Minor update in Performance Specifications 0303
November 2020 Minor update in Fluid selection 0302
August 2020 Update CPRV setting 0301
June 2020 Changed document number and version from 'BC00000191' and 'L1104976' to
'BC152886484876'
August 2019 Minor typo 0105
June 2019 Added Size 24 0104
December 2018 Corrected rounding error in performance specifications 0103
February 2017 Change charge pump housing 0102
January 2016 Add SAE-A, 13T Auxiliary Pad Option 0101
April 2015 Minor update in Model Code BB
March 2015 Add Implement Pump and SAE A Mounting Flange Options, and Converted to Danfoss
layout - DITA CMS
March 2013 Paint and Tag AC
November 2011 Minor edits AB
October 2011 First edition AA
0201
BA
2 | © Danfoss | February 2022 BC152886484876en-000309
Technical Information
DDC Axial Piston Pumps Size 20/24
Contents
General Description
Design...................................................................................................................................................................................................5
Key Features....................................................................................................................................................................................... 5
Typical Applications........................................................................................................................................................................ 5
System Diagram................................................................................................................................................................................6
Schematic Diagram..........................................................................................................................................................................7
Technical Specifications
Design Specifications......................................................................................................................................................................8
Performance Specifications..........................................................................................................................................................8
Operating Parameters.....................................................................................................................................................................9
Fluid Specifications..........................................................................................................................................................................9
Operation
High Pressure Relief / Check Valve (HPRV)............................................................................................................................10
High pressure relief / check valve with orifice............................................................................................................... 10
Bypass Function..............................................................................................................................................................................11
Charge Pressure Relief Valve (CPRV)....................................................................................................................................... 12
Loop flushing valve.......................................................................................................................................................................13
Control............................................................................................................................................................................................... 14
Direct Displacement Control................................................................................................................................................14
Control Handle Requirements............................................................................................................................................. 14
Operating Parameters
Overview........................................................................................................................................................................................... 15
Input speed...................................................................................................................................................................................... 15
System pressure............................................................................................................................................................................. 15
Charge pressure..............................................................................................................................................................................15
Charge pump inlet pressure...................................................................................................................................................... 16
Case pressure...................................................................................................................................................................................16
Temperature.................................................................................................................................................................................... 16
Viscosity.............................................................................................................................................................................................16
System Design Parameters
Filtration system ............................................................................................................................................................................17
Filtration............................................................................................................................................................................................ 18
Suction filtration....................................................................................................................................................................... 18
Charge pressure filtration......................................................................................................................................................18
External Pressure Filtration................................................................................................................................................... 19
Independent braking system.................................................................................................................................................... 19
Fluid Selection.................................................................................................................................................................................19
Reservoir............................................................................................................................................................................................19
Case Drain.........................................................................................................................................................................................19
Charge Pump...................................................................................................................................................................................20
Charge Pump Sizing/Selection............................................................................................................................................20
Charge Pump Output Flow........................................................................................................................................................ 20
Implement Pump...........................................................................................................................................................................21
Bearing Loads and Life.................................................................................................................................................................23
Applications with External Shaft Loads............................................................................................................................23
Input Shaft...................................................................................................................................................................................23
Shaft Torque.....................................................................................................................................................................................24
Mounting Flange Loads...............................................................................................................................................................25
Estimating Overhung Load Moments...............................................................................................................................25
Understanding and minimizing system noise.....................................................................................................................26
Size Equations................................................................................................................................................................................. 27
Model Code
Model Code: A, B, R, C, E, G, M................................................................................................................................................... 28
Model Code: H, K, F........................................................................................................................................................................29
Model Code: J, S, L......................................................................................................................................................................... 30
Model Code: N, P, Y, Z...................................................................................................................................................................31
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Danfoss | February 2022 BC152886484876en-000309 | 3
Technical Information
DDC Axial Piston Pumps Size 20/24
Contents
Installation Drawings
With Aux-Pad, No Charge Pump, Left Trunnion, SAE A Flange Configuration........................................................32
With Aux-Pad, No Charge Pump, Left Trunnion, SAE B Flange Configuration........................................................ 34
With Charge Pump, No Aux-Pad, Left Trunnion, SAE A Flange Configuration........................................................36
With Charge Pump, No Aux-Pad, Left Trunnion, SAE B Flange Configuration........................................................ 38
With Implement Pump, No Aux-Pad, Left Trunnion, SAE A Flange Configuration................................................40
With Implement Pump, No Aux-Pad, Left Trunnion, SAE B Flange Configuration................................................ 42
Option: Detent................................................................................................................................................................................ 44
Input Shafts: AA, BA, DA.............................................................................................................................................................. 45
Input Shafts: AB, BB, DB............................................................................................................................................................... 46
Input Shafts: AC, BC, DC...............................................................................................................................................................47
Auxiliary Mounting Pads............................................................................................................................................................. 48
Reference Literature
Literature...........................................................................................................................................................................................50
4 | © Danfoss | February 2022 BC152886484876en-000309
Bypass valve
SlipperValve plate
Trunnion
Charge pump
Needle bearing
Piston
Swashplate
Check and high pressure relief valve
Input
shaft
Ball bearingCharge pressure relief valve
Endcap
P400023
Technical Information
DDC Axial Piston Pumps Size 20/24
General Description
Design
The DDC pump is a compact and lightweight variable displacement axial piston pump intended for use
in closed circuit low to medium power applications. DDC pump is a direct displacement control pump
utilizing an advanced slipper piston design. The flow rate is infinitely variable between zero and
maximum. The direction of flow is commanded by tilting the swashplate in one direction or the other
from the neutral (zero flow) position. Reversing the direction of flow reverses the direction of motor
rotation.
Key Features
Displacement 20/24 cm3/rev [1.22/1.46 in3/rev]
•
Optional bypass valve and loop flushing valve
•
Optional integral charge pump / Implement pump
•
Compact design with best in class pressure ratings and durability
•
Low noise
•
Backed by a global network of Danfoss service provider
•
Mounting flange (SAE-A / B)
•
Typical Applications
DDC Pump Cross-Sectional View
Turf Care
•
Greens Mower
‒
Zero Turn Radius Mower
‒
Loaders
‒
Utility Vehicles
•
Compact Agricultural Machinery
•
Small Compactors
•
Compact Construction Equipment
•
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Danfoss | February 2022 BC152886484876en-000309 | 5
Variable
displacement
pump
Input
shaft
Cylinder
block
assembly
High pressure relief/
check valves
Loop flushing valve
OMR
orbital
motor
Suction flow
Working Loop (High Pressure)
Case flow
Working Loop (Low Pressure) and
Charge Pressure
Output
shaft
Filter
Charge
pump
Reservoir
Heat
exchanger
Heat exchanger
bypass
Charge pressure relief
valve
Bypass
valve
P400024
Technical Information
DDC Axial Piston Pumps Size 20/24
General Description
System Diagram
Loop flushing valve and Charge pump cannot be used together in one pump.
6 | © Danfoss | February 2022 BC152886484876en-000309
A
B
M3
MA
MB
L1
L3
L2
S
P400025
Technical Information
DDC Axial Piston Pumps Size 20/24
General Description
Schematic Diagram
Loop flushing valve and Charge pump cannot be used together in one pump.
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Danfoss | February 2022 BC152886484876en-000309 | 7
Technical Information
DDC Axial Piston Pumps Size 20/24
Technical Specifications
Design Specifications
Features DDC pump
Design Axial piston pump of journal trunnion design with variable displacement
Direction of input rotation Clockwise or counterclockwise
Pump installation position is discretionary, however the recommended trunnion position
is on the side or at the bottom.
If mounted with trunnion shaft position upward, water and dust tend to collect around
Recommended installation position
Filtration configuration Suction or charge pressure filtration
Other system requirements Independent braking system, suitable reservoir and heat exchanger
Control type Direct displacement control
Performance Specifications
Features Units DDC20 DDC24
Displacement
Mass moment of inertia of rotating components kg•m2 [slug•ft2] 0.0009 [0.0006]
Weight dry
Oil volume Case only liter [US gal] 0.7 [0.1]
Mounting flange
Input shaft outer diameter, Splines, key shafts
Auxiliary mounting flange with metric fasteners, shaft outer
diameter and splines
Suction ports ISO 11926-1, 7/8 -14 (SAE O-ring boss)
Main port configuration ISO 11926-1, 7/8 -14 (SAE O-ring boss) Twin port, radial
Case drain ports L1, L2 , L3 ISO 11926-1, 3/4 -16 (SAE O-ring boss)
Other ports See Installation Drawings on page 32
Customer interface threads Metric fasteners
1
Max Swashplate angle is 18 degrees.
2
See Installation Drawings on page 32 for mounting flange SAE A.
1
With charge pump
With implement pump 11 [24.3]
With auxiliary pad 12 [26.4]
2
the shaft, which may accelerate the deterioration of the shaft seal.
Vertical input shaft installation is acceptable. The housing must always be filled with
hydraulic fluid. Recommended mounting for a multiple pump stack is to arrange the
highest power flow towards the input source.
Consult Danfoss for nonconformance to these guidelines.
cm3/rev [in3/rev] 0-20.0 [0-1.22] 0-24.0 [0-1.46]
10 [22.1]
kg [lb]
ISO3019-1 flange 101-2 (SAE B), 2 bolt
ISO3019-1 flange 82-2 (SAE A), 2 bolt
ISO 3019-1, outer dia 22mm-4 (SAE B, 13 teeth)
ISO 3019-1, outer dia 22mm-1 (Straight Key, Ls)
ISO 3019-1, outer dia 22mm-1 (Straight Key, Special length)
ISO 3019-1, flange 82 - 2, outer dia 16 mm - 4
(SAE A, 9 teeth)
ISO 3019-1, flange 82 - 2, outer dia 19 mm - 4
(SAE A, 11 teeth)
8 | © Danfoss | February 2022 BC152886484876en-000309
Technical Information
DDC Axial Piston Pumps Size 20/24
Technical Specifications
Operating Parameters
For definitions of the following specifications, see Operating Parameters on page 15
Features Units DDC pump
Minimum for internal charge
1
supply
Input speed
Minimum for external
charge supply
min-1 (rpm)
Rated 4000
Maximum 4500
Maximum working pressure
System pressure
Maximum pressure 345 [5004]
bar [psi]
Minimum low loop (above
case)
Charge pressure (minimum) bar@15 lpm [psi/USG] 7 [101]
Minimum (continuous)
Charge pump inlet pressure
Minimum (cold start) 0.2 [24]
bar (absolute) [in Hg vacuum]
Maximum 2.0
Case pressure
1
No load condition. Refer to System Design Parameters/Charge Pump on page 20 for details.
Rated
Maximum 3 [43.5]
bar [psi]
500
500
300 [4350]
4 [58]
0.8 [6]
1.5 [21.7]
Fluid Specifications
Features Units DDC pump
intermittent
Viscosity
Minimum 7 [49]
Recommended range 12 - 80 [66 - 370]
Maximum (cold start)
Maximum (cold start)
Temperature range
3
Recommended range 60 - 85
Maximum continuous 104
Maximum intermittent
Cleanliness per ISO 4406 22/18/13
Efficiency (charge pressure
Filtration (recommended
minimum)
filtration)
Efficiency (suction filtration) β35-45=75(β10≥2)
Rercommended inlet screen
mesh size
1
Intermittent=Short term t <1 min per incident and not exceeding 2 % of duty cycle based load-life.
2
Cold start = Short term t < 3 min, p < 50 bar [725 psi], n < 1000 min-1 (rpm)
3
At the hottest point, normally case drain port.
1
5 [42]
mm2/sec. [ SUS]
2
1600 [7500]
-20
°C
115
β-ratio
β15-20=75(β10≥10)
µm 100 - 125
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Danfoss | February 2022 BC152886484876en-000309 | 9
P400026
C
W
Technical Information
DDC Axial Piston Pumps Size 20/24
Operation
High Pressure Relief / Check Valve (HPRV)
The DDC pump is equipped with a combination high pressure relief and charge check valve. The high
pressure relief valve (HPRV) function is a dissipative (with heat generation) direct acting pressure control
valve for the purpose of limiting excessive system pressures. Each side of the transmission loop has a
non-adjustable HPRV valve. When system pressure exceeds the factory setting of the valve, oil flows into
the charge gallery. The valve is a differential pressure device working with system and charge pressure.
The charge check function acts to replenish the low-side working loop with oil any time the low loop
pressure falls below charge pressure.
Different pressure relief settings may be used at each system port. The order code specifies HPRV
pressure setting availability.
High pressure relief / check valve with orifice
A HPRV valve with an orifice is available as an option. In some applications, it is desirable to use a HPRV/
Check with an orifice to allow for easier neutral adjustment. The orifice connects the working loop to the
charge gallery. It allows a small amount of loop leakage which expands the dead band around the neutral
position of the swashplate. Most applications find it suitable to configure only one side of the system
loop with an orificed HPRV. An orifice referenced to the high pressure side of the loop will decrease
effective efficiency of the system and increase heat into the system. By locating an orifice only on the
reverse drive side of the loop, system efficiency losses are minimized. Increased downhill creep may also
be present.
The HPRV are set at the following flow rates
Check/HPRV without orifice 5 l/min [1.3 US gal/min]
Check/HPRV with orifice 17 l/min [4.5 US gal/min]
Caution
HPRV´s are factory set at a low flow condition. Any application or operating condition which leads to
elevated HPRV flow will cause a pressure rise above the factory setting. Contact your Danfoss
representative for an application review. Using an HPRV with an orifice may increase downhill creep.
Warning
Unintended vehicle or machine movement hazard.
The vehicle must include a braking system redundant to the hydrostatic transmission, sufficient to stop
and hold the vehicle or machine in the event of hydrostatic drive power loss.
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System Loop (Low Pressure)
Bypass Valve
System Loop (High Pressure)
P400027
C
Technical Information
DDC Axial Piston Pumps Size 20/24
Operation
Bypass Function
In some applications it is desirable to bypass the hydraulic fluid around the pump so the machine/load
can be moved without rotating the pump shaft or prime mover. An optional bypass valve mechanically
connects both A & B sides of the system pressure together. The bypass is fully opened when the valve is
turned (opened) counterclockwise 3 revolutions. The valve must be fully closed for normal operation.
Refer to the DDC pump outline drawings for location of the bypass valve.
Bypass valve wrench size and torque
Wrench size Torque N•m [lbf•ft]
17 mm external 12.0 [9.0]
Caution
Excessive speed or extended movement will damage the pump and motor(s)
Avoid excessive speeds and extended load/vehicle movement when using the bypass function. Damage
to the drive motor is possible if the load or vehicle is moved at a speed greater than 20% of maximum or
for a duration exceeding 3 minutes..
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Danfoss | February 2022 BC152886484876en-000309 | 11
Charge Pressure
Case Drain
P400028
C
Technical Information
DDC Axial Piston Pumps Size 20/24
Operation
Charge Pressure Relief Valve (CPRV)
An internal charge pressure relief valve (CPRV) regulates charge pressure within the hydraulic circuit. The
CPRV is a direct acting poppet valve that regulates charge pressure at a designated level above case
pressure.
The charge pressure relief valve setting is specified within the model code of the pump. DDC pumps with
charge pump have the CPRV set at 1800 rpm while DDC pumps without charge pump have the CPRV set
with below external charge supply.
Charge pressure setting in MMC [bar] External charge flow [L/min]
7 8.6
11, 14, 18, 21 13.5
The 7 bar charge pressure rise rate, with flow, is approximately 0.8 bar/10 liter [4.4 psi/US gal].
The 11 and 14 bar charge pressure rise rate, with flow, is approximately 1.4 bar /10 liter [7.7 psi/US gal].
The 18 and 21 bar charge pressure rise rate, with flow, is approximately 1.6 bar/10 liter [8.8 psi/US gal] .
Caution
When a DDC pump is used with a variable motor, ensure the available charge pressure matches the
required motor shift pressure. Contact your Danfoss representative for the availability of additional
charge relief settings.
12 | © Danfoss | February 2022 BC152886484876en-000309
Working Loop (Low Pressure)
Working Loop (High Pressure)
Case
Notched Diameter
P400029
Oil Temp = 50°C (~30 mm2
/S)
P400301
Flow [lpm]
Charge pressure [d bar]
Technical Information
DDC Axial Piston Pumps Size 20/24
Operation
Loop flushing valve
DDC pumps are available with an optional integral loop flushing. A loop flushing valve will remove heat
and contaminants from the main loop at a rate faster than otherwise possible.
The DDC loop flushing design is a simple spring centered shuttle spool with an orifice plug. The shuttle
shifts at approximately 8 bar [115 psi]. The flushing flow is a function of the low loop system pressure
(charge) and the size of the plug.
Loop flushing valve is not available with charge pump combination.
Loop flushing performance
When a DDC pump is used with an external loop flushing shuttle valve, ensure that the charge setting of
the pump matches the setting of the loop flushing shuttle valve. Contact your Danfoss representative for
the availability of additional charge relief settings.
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Danfoss | February 2022 BC152886484876en-000309 | 13
-50
-40
-30
-20
-10
0
10
20
30
40
50
-20 -15 -10 -5 0 5 10 15 20
<pumping mode>
35 bar
6 bar
50 bar
100 bar
200 bar
300 bar
<a>
<b>
Stroke increasing moment
Stroke increasing moment
Stroke decreasing moment
Stroke decreasing moment
Trunnion moment (N•m)
Angle (deg)
P400030
a b
Technical Information
DDC Axial Piston Pumps Size 20/24
Operation
Control
Direct Displacement Control
The DDC pump features direct displacement control (DDC) .The swashplate angle is set directly by a
linkage attached to the swashplate trunnion. Moving the control lever changes the displacement and
direction of flow.
The input shaft is configurable to the left or right side of the pump.
Control Handle Requirements
All DDC pumps will transfer hydraulic forces from within the transmission into the pump control arm
where these forces are seen as a control arm torque. The nature and magnitude of the control arm torque
is a function of transmission operating conditions (pump speed, pressure and displacement) and design
of the DDC valve plate. During normal operation the control arm torque will be stroke reducing, whereas
dynamic braking and downhill operation likely will result in stroke increasing control arm feedback. The
driver and/or the mechanical linkage must be able to return the pump to neutral under all conditions.
Contact Danfoss for additional application support regarding lower control arm torque options.
Maximum allowable control arm torque, applied from the customer linkage, is 79.1 Nm (700 in-lbs).
Linkage stops may be required to limit input torque to the control arm. Maximum swashplate angle is +/18 degrees.
DDC Pumps Control Moment
Input=2000 rpm, Temp=50°C, Shell Tellus 46 Viscosity=30m 2/s
Stroking Speed=1deg/sec, Standard HPRV
14 | © Danfoss | February 2022 BC152886484876en-000309
W
Technical Information
DDC Axial Piston Pumps Size 20/24
Operating Parameters
Overview
This section defines the operating parameters and limitations with regard to input speeds and pressures.
Input speed
Minimum speed is the lowest input speed recommended during engine idle condition. Operating below
minimum speed limits pump’s ability to maintain adequate flow for lubrication and power transmission.
Rated speed is the highest input speed recommended at full power condition. Operating at or below
this speed should yield satisfactory product life.
Maximum speed is the highest operating speed permitted. Exceeding maximum speed reduces product
life and can cause loss of hydrostatic power and braking capacity. Never exceed the maximum speed
limit under any operating conditions.
Operating conditions between Rated speed and Maximum speed should be restricted to less than full
power and to limited periods of time. For most drive systems, maximum unit speed occurs during
downhill braking or negative power conditions.
During hydraulic braking and downhill conditions, the prime mover must be capable of providing
sufficient braking torque in order to avoid pump over speed. This is especially important to consider for
turbocharged and Tier 4 engines.
System pressure
Warning
Unintended vehicle or machine movement hazard.
Exceeding maximum speed may cause a loss of hydrostatic drive line power and braking capacity. You
must provide a braking system, redundant to the hydrostatic transmission, sufficient to stop and hold the
vehicle or machine in the event of hydrostatic drive power loss.
System pressure is the differential pressure between system ports A and B. It is the dominant operating
variable affecting hydraulic unit life. High system pressure, which results from high load, reduces
expected life. Hydraulic unit life depends on the speed and normal operating, or weighted average,
pressure that can only be determined from a duty cycle analysis.
Application pressure is the high pressure relief setting normally defined within the order code of the
pump. This is the applied system pressure at which the driveline generates the maximum calculated pull
or torque in the application.
Maximum working pressure is the highest recommended Application pressure. Maximum working
pressure is not intended to be a continuous pressure. Propel systems with Application pressures at, or
below, this pressure should yield satisfactory unit life given proper component sizing.
Maximum pressure is the highest allowable Application pressure under any circumstance. Application
pressures above Maximum Working Pressure will only be considered with duty cycle analysis and factory
approval. Pressure spikes are normal and must be considered when reviewing maximum working
pressure.
All pressure limits are differential pressures referenced to low loop (charge) pressure. Subtract low loop
pressure from gauge readings to compute the differential.
Minimum low loop pressure (above case pressure) is the lowest pressure allowed to maintain a safe
working condition in the low side of the loop.
Charge pressure
An internal charge relief valve regulates charge pressure. Charge pressure maintains a minimum pressure
in the low side of the transmission loop.
The charge pressure setting listed in the order code is the set pressure of the charge relief valve with the
pump in neutral, operating at 1800 min-1 [rpm], and with a fluid viscosity of 32 mm2/s [150 SUS]. Pumps
©
Danfoss | February 2022 BC152886484876en-000309 | 15
C
Technical Information
DDC Axial Piston Pumps Size 20/24
Operating Parameters
configured with no charge pump (external charge supply) are set with a charge flow of 18.9 l/min [5.0 US
gal/min] and a fluid viscosity of 32 mm2/s [150 SUS].
The charge pressure setting is referenced to case pressure.
Charge pump inlet pressure
At normal operating temperature charge inlet pressure must not fall below rated charge inlet pressure
(vacuum).
Minimum charge inlet pressure is only allowed at cold start conditions. In some applications it is
recommended to warm up the fluid (e.g. in the tank) before starting the engine and then run the engine
at limited speed until the fluid warms up.
Maximum charge pump inlet pressure may be applied continuously.
Case pressure
Under normal operating conditions, the rated case pressure must not be exceeded. During cold start case
pressure must be kept below maximum intermittent case pressure. Size drain plumbing accordingly.
Caution
Temperature
Viscosity
Possible component damage or leakage
Operation with case pressure in excess of stated limits may damage seals, gaskets, and/or housings,
causing external leakage. Performance may also be affected since charge and system pressure are
additive to case pressure.
The high temperature limits apply at the hottest point in the transmission, which is normally the motor
case drain. The system should generally be run at or below the rated temperature.
The maximum intermittent temperature is based on material properties and should never be
exceeded.
Cold oil will not affect the durability of the transmission components, but it may affect the ability of oil to
flow and transmit power; therefore temperatures should remain 16 °C [30 °F] above the pour point of the
hydraulic fluid.
The minimum temperature relates to the physical properties of component materials. Size heat
exchangers to keep the fluid within these limits. Danfoss recommends testing to verify that these
temperature limits are not exceeded.
Ensure fluid temperature and viscosity limits are concurrently satisfied.
Viscosity For maximum efficiency and bearing life, ensure the fluid viscosity remains in the
recommended range.
The minimum viscosity should be encountered only during brief occasions of maximum ambient
temperature and severe duty cycle operation.
The maximum viscosity should be encountered only at cold start.
16 | © Danfoss | February 2022 BC152886484876en-000309
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