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	0201
			'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	BA
			layout - DITA CMS
	March 2013		Paint and Tag	AC
	November 2011		Minor edits	AB
	October 2011		First edition	AA

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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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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

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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

•Turf Care

‒Greens Mower

‒Zero Turn Radius Mower

‒Loaders

•Utility Vehicles

•Compact Agricultural Machinery

•Small Compactors

•Compact Construction Equipment

DDC Pump Cross-Sectional View

Trunnion

Valve plate	Piston	Slipper
		Charge pump

Charge pressure relief valve Ball bearing

Input shaft

		Swashplate		Endcap			Needle bearing
Check and high pressure relief valve							Bypass valve	P400023

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DDC Axial Piston Pumps Size 20/24

General Description

System Diagram

		Heat exchanger		Reservoir
		bypass
				Filter
		Heat
		exchanger
				Charge pressure relief
Cylinder				valve
block						OMR
assembly
						orbital
						motor
				Charge pump
						Output
						shaft
					Suction flow
Input	Variable	High pressure relief/	Loop flushing valve		Working Loop (Low Pressure) and
shaft	displacement	check valves			Charge Pressure
	pump				Working Loop (High Pressure)
					Case flow	P400024

Loop flushing valve and Charge pump cannot be used together in one pump.

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DDC Axial Piston Pumps Size 20/24

General Description

Schematic Diagram

L3

M3

MA

A

B

L1	L2	S	MB	P400025

Loop flushing valve and Charge pump cannot be used together in one pump.

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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	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.
	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
Displacement1		cm3/rev [in3/rev]	0-20.0 [0-1.22]	0-24.0 [0-1.46]
Mass moment of inertia of rotating components		kg•m2 [slug•ft2]	0.0009 [0.0006]
	With charge pump		10 [22.1]
Weight dry	With implement pump	kg [lb]	11 [24.3]
	With auxiliary pad		12 [26.4]
Oil volume	Case only	liter [US gal]	0.7 [0.1]
Mounting flange		ISO3019-1 flange 101-2 (SAE B), 2 bolt
		ISO3019-1 flange 82-2 (SAE A), 2 bolt
Input shaft outer diameter, Splines, key shafts2		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
Auxiliary mounting flange with metric fasteners, shaft outer		(SAE A, 9 teeth)
diameter and splines		ISO 3019-1, flange 82 - 2, outer dia 19 mm - 4
		(SAE A, 11 teeth)
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

1Max Swashplate angle is 18 degrees.

2See Installation Drawings on page 32 for mounting flange SAE A.

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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		500
		supply1
	Input speed	Minimum for external	min-1 (rpm)	500
		charge supply
		Rated		4000
		Maximum		4500
		Maximum working pressure		300 [4350]
	System pressure	Maximum pressure	bar [psi]	345 [5004]
		Minimum low loop (above		4 [58]
		case)
	Charge pressure (minimum)		bar@15 lpm [psi/USG]	7 [101]
		Minimum (continuous)		0.8 [6]
	Charge pump inlet pressure	Minimum (cold start)	bar (absolute) [in Hg vacuum]	0.2 [24]
		Maximum		2.0
	Case pressure	Rated	bar [psi]	1.5 [21.7]
		Maximum		3 [43.5]

1 No load condition. Refer to System Design Parameters/Charge Pump on page 20 for details.

Fluid Specifications

	Features		Units	DDC pump
		intermittent1		5 [42]
	Viscosity	Minimum	mm2/sec. [ SUS]	7 [49]
		Recommended range		12 - 80 [66 - 370]
		Maximum (cold start)2		1600 [7500]
		Maximum (cold start)		-20
	Temperature range3	Recommended range	°C	60 - 85
		Maximum continuous		104
		Maximum intermittent		115
		Cleanliness per ISO 4406		22/18/13
		Efficiency (charge pressure		β15-20=75(β10≥10)
	Filtration (recommended	filtration)	β-ratio
	minimum)	Efficiency (suction filtration)		β35-45=75(β10≥2)
		Rercommended inlet screen	µm	100 - 125
		mesh size

1Intermittent=Short term t <1 min per incident and not exceeding 2 % of duty cycle based load-life.

2Cold start = Short term t < 3 min, p < 50 bar [725 psi], n < 1000 min-1 (rpm)

3At the hottest point, normally case drain port.

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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]

P400026

C 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.

W 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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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
System Loop (High Pressure)	System Loop (Low Pressure)
		P400027
Bypass valve wrench size and torque
Wrench size		Torque N•m [lbf•ft]
17 mm external		12.0 [9.0]

C 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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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] .

Case Drain

Charge Pressure

P400028

C 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.

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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.

Notched Diameter

Working Loop (Low Pressure)

Case

Working Loop (High Pressure)

P400029

Loop flushing valve is not available with charge pump combination.

Loop flushing performance

Oil Temp = 50°C (~30 mm2/S)

<![if ! IE]> <![endif]>Flow [lpm]

Charge pressure [d bar]

P400301

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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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

				<a>		<pumping mode>		<b>
			Stroke decreasingmoment			50	Stroke increasingmoment
						40		a	b	6 bar
						30				35 bar
										50 bar
	<![if ! IE]> <![endif]>(N•m)
						20				100 bar
										200 bar
	<![if ! IE]> <![endif]>moment					10				300 bar
						0
		-20	-15	-10	-5	0	5	10	15	20
	<![if ! IE]> <![endif]>Trunnion
						-10
						-20
						-30
						-40
			Stroke increasingmoment			-50		Stroke decreasingmoment
						Angle (deg)				P400030

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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.

W 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

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

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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.

C Caution

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.

Temperature

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

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.

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