421AK00061A Sauer Danfoss 41cc Piston Pump 280bar

Product Overview

The 421AK00061A is a Sauer Danfoss (now Danfoss Power Solutions) Series 420 open-circuit axial piston pump with a displacement of 41 cm³/rev, belonging to the X20 portfolio of mobile hydraulic pumps. The 420 series features a cradle bearing design for a compact, space-saving package with high power density. It is available in 41cc, 62cc, and 80cc displacements with a variety of control options to match performance to a broad range of mobile applications. This model carries the “421AK” prefix, corresponding to Series 420 code C design revision, equipped with a 2-bolt SAE-B mounting flange and 13-tooth 16/32 spline shaft.

Related models in the series include: 421AK02502C (41cc, left-hand rotation, 280 bar working pressure, weight 22.9 kg); 421AK00018C (62.3 cm³/rev, right-hand rotation, SAE-B mounting, pressure and flow compensator); and 421AK00311A (420AK/421AK series, applicable to excavators and other mobile equipment). The 421AK00018C is equipped with a pressure and flow compensator featuring an LS load-sensing port, with pressure compensator setting of 275.8–282.7 bar and flow compensator setting of 12.41–15.17 bar.

Manufactured to original Sauer Danfoss specifications with guaranteed drop-in interchangeability, this pump directly replaces the OEM 421AK series pump without modification to mounting interfaces or hydraulic plumbing. Every unit undergoes 100% simulated working-condition dyno testing prior to shipment, including rated pressure cycling, control response verification, and leakage inspection.

Technical Specifications

421AK00061A Primary Parameters (Inferred):

• Model: 421AK00061A

• Series: Sauer Danfoss Series 420 (X20 Portfolio)

• Type: Open-circuit axial piston pump

• Displacement: 41 cm³/rev (2.50 in³/rev)

• Design Code: C

• Mounting Flange: 2-bolt SAE-B (SAE J744-101-2)

• Shaft Type: 13-tooth 16/32 spline (ANSI B92.1-1996 MOD)

• Shaft Extension: 41.1 mm [1.62 in]

• Control Type: Pressure and flow compensator (with LS load-sensing port)

• Rated Pressure: 280 bar [4,060 psi]

• Peak Pressure: 350 bar [5,075 psi]

• Speed Range: 600–3,600 rpm

• Max Speed (specific condition): 2,950 rpm (@ 2.0 bar absolute inlet)

• Min. Flow Compensator Setting: 12.41 bar

• Max. Flow Compensator Setting: 15.17 bar

• Pressure Compensator Setting Range: 275.8–282.7 bar

• Housing Material: Cast Iron

• Weight: Approx. 22.9 kg

• Seal Material: Polyacrylate (standard) or fluorocarbon (optional)

• Port Configuration: Inlet 2.00″ SAE J518 4-bolt split flange (Code 61); Pressure 1.00″ SAE J518 4-bolt split flange (Code 61)

• Drain Port: 1.0625-12 UNF-2B O-ring port, top

• Fluid Cleanliness: ISO 4406 21/18/13

421AK02502C Primary Parameters:

• Model: 421AK02502C

• Displacement: 41 cm³/rev

• Working Pressure: 280 bar

• Rotation: Left Hand (L)

• Mounting Flange: 2-bolt SAE-B

• Shaft Type: 13-tooth 16/32 spline

• Weight: 22.9 kg

• Ports: AB – Side Ports; Inlet 2″ (Code 61); Pressure 1″ (Code 61)

421AK00018C Primary Parameters:

• Model: 421AK00018C

• Displacement: 62.3 cm³/rev (3.80 in³/rev)

• Design Code: C

• Rotation: Right Hand (CW)

• Mounting Flange: 2-bolt SAE-B (SAE J744-101-2) and 13-tooth 16/32 spline

• Shaft Extension: 41.1 mm [1.62 in]

• Control Type: Pressure and flow compensator (with LS load-sensing port, left side)

• Pressure Compensator Setting: 275.8–282.7 bar

• Flow Compensator Setting: 12.41–15.17 bar

• Ports: Rear ports; Inlet 2.00″ SAE J518 4-bolt split flange (Code 61); Pressure 1.00″ SAE J518 4-bolt split flange (Code 61)

• Drain Port: 1.0625-12 UNF-2B O-ring port, top

• Seal Material: Standard polyacrylate

421AK00311A Primary Parameters (Inferred):

• Model: 421AK00311A

• Series: 420AK/421AK Series

• Type: Open-circuit axial piston pump (for excavators and other mobile equipment)

• Displacement: 41 cm³/rev to 80 cm³/rev (series range)

• Control Type: Pressure compensated / pressure and flow compensated

• Rated Pressure: 280 bar

Series 420 Common Specifications:

• Displacement Range: 41cc, 62cc, 80cc

• Rated Pressure: 280 bar [4,060 psi]

• Peak Pressure: 350 bar [5,075 psi]

• Speed Range: 600–3,600 rpm

• Housing Material: Cast Iron

• Seal Material: Polyacrylate or fluorocarbon

• Max Case Drain Temperature: 220°F [104°C]

• Fluid Cleanliness: 21/18/13

• Recommended Operating Viscosity: 16–40 cSt

• Control Options: Pressure compensator, pressure and flow compensator (with LS port), pressure and flow compensator with torque control

• Rotation: Clockwise (CW) or counter-clockwise (CCW) options

• Auxiliary Mounting: SAE-A or SAE-B 2-bolt, 9T or 13T 16/32 spline

Key Technical Advantages

1. Cradle Bearing Compact Design with High Power Density

The 420 series utilizes a cradle bearing design, resulting in a compact, space-saving pump package with high power density. This design enables greater hydraulic power transmission within a limited installation envelope, particularly suited for space-constrained mobile hydraulic applications. The X20 portfolio’s 420 series pumps are engineered for “superior reliability and productivity in a compact package,” meeting equipment engineers’ demands for greater power density.

2. Pressure and Flow Compensation Control — Power on Demand

The 421AK series features pressure and flow compensator control, integrating both pressure compensation and flow compensation functions. The pressure compensator is set at 275.8–282.7 bar, the flow compensator at 12.41–15.17 bar, with the LS load-sensing port on the left side. The pump delivers only the flow and pressure actually required by the system; excess flow is automatically eliminated by reducing the swashplate angle to near-zero displacement. This fundamentally eliminates the energy waste associated with fixed-displacement pumps that dump excess flow through relief valves, significantly reducing system heat generation.

3. Precision-Machined Rotary Group with High Volumetric Efficiency

The 420 series’ critical rotating components — including the cylinder block, pistons, valve plate, and drive shaft — are precision-machined to OEM tolerances. Cylinder bores are precision-honed with micron-level clearances, minimizing internal leakage. A stable hydrodynamic lubrication film forms between the pistons and cylinder block, maintaining high volumetric efficiency at 280 bar rated pressure. The pump features a response time of 20 ms for rapid response and recovery capability.

4. Low-Noise Operation and Long Service Life

The 420 series effectively suppresses pressure pulsation and fluid-borne noise through optimized valve plate flow passage geometry and cradle bearing construction. Low noise levels are maintained even at the maximum speed of 3,600 rpm. Polyacrylate or fluorocarbon seals accommodate high-temperature applications, and the precision-machined bearing system ensures long service life under demanding operating conditions. Bearing life at rated pressure is rated at 10,280 hours.

5. Modular Auxiliary Mounting Pads for Flexible Configuration

The 420 series offers SAE-A or SAE-B auxiliary mounting pads (2-bolt, 9T or 13T 16/32 spline), allowing auxiliary pumps (such as gear pumps or a second piston pump) to be bolted directly to the rear of the main pump, forming a compact tandem assembly without separate support brackets or additional drive interfaces. This modular design significantly reduces axial installation length, reducing system complexity and installation costs.

Application Areas

The 421AK00061A, 421AK02502C, 421AK00018C, and 421AK00311A are widely used in the following equipment:

• Telescopic handlers

• Aerial lifts

• Wheel loaders

• Mini excavators

• Backhoe loaders

• Skid steer loaders

• Combines and harvesters

• Sprayers and agricultural machinery

• Snow removal trucks, refuse trucks, and fire trucks

• Railcar movers

• Material handling equipment

• Cranes

• Mobile mining equipment

Expert Maintenance Tips

Pre-Installation Checks: Verify that the pump shaft spline matches the drive end configuration (13-tooth 16/32 spline, ANSI B92.1-1996 MOD) before installation. Apply a light coating of grease to the spline surface. Ensure full contact between the mounting flange and the mounting pad. Tighten fixing bolts to the specified torque values. Never force the pump into position by tightening the fixing bolts, as this may cause abnormal bearing preload or housing deformation. Confirm that the rotation direction (L = left-hand or R = right-hand, viewed from shaft end) matches the drive end.

Oil Cleanliness Control: The recommended fluid cleanliness for the 420 series is ISO 4406 21/18/13. System oil cleanliness should be maintained at or better than this level to ensure service life of the piston/cylinder assemblies and valve plate. Suction filters should be rated at 10 μm or finer; return-line filters at 10 μm or finer are recommended. Check suction line sealing before first start-up to prevent air ingress. The minimum absolute inlet pressure is 0.8 bar (at reduced maximum speed), or 0.5 bar absolute for cold start.

Case Drain Management: The case drain line must remain unrestricted and should be routed directly to the reservoir below the oil level to avoid backpressure affecting pump displacement control. The maximum allowable continuous case pressure is 0.5 bar (above inlet pressure), with higher values permitted intermittently. Maximum case drain temperature is 220°F [104°C] — if exceeded, stop the machine immediately and investigate. Periodically inspect the drain line for loosening or wear caused by vibration.

Control Mechanism Maintenance: Periodically inspect pressure and flow compensator and LS load-sensing control line connections for tightness. No leakage or blockage should exist in the control circuit. An LS setting of no less than 15 bar is recommended to enhance system stability; a 20 bar LS setting is recommended as a starting point for all new applications. If sluggish flow response, unstable pressure, or system oscillation is observed, first inspect the control lines, damping orifices, and compensator valve.

Start-Up and Break-In: During initial start-up, operate at low speed and low pressure for 10–15 minutes to purge air from the system and check all connections for leakage. Fill the pump case with clean hydraulic oil through the case drain port before starting to prevent dry-start damage to the rotary group. The recommended operating viscosity range is 16–40 cSt; when hydraulic fluid viscosity exceeds 200 cSt, a no-load warm-up period is required before applying load. With a pump weight of approximately 22.9 kg, use appropriate lifting equipment during handling and installation.