Rexroth A4VG125DA2D2-32L-NAF021DT Overview

This is a Series 32​ closed‑circuit, swashplate‑type axial‑piston variable pump​ from Bosch Rexroth’s A4VG family, size 125 cm³/rev. It is designed for hydrostatic drive systems​ with a nominal pressure of 400 bar​ and a maximum pressure of 450 bar. The pump delivers flow proportional to drive speed and displacement, and the swashplate can be moved through neutral to reverse flow direction smoothly. Typical uses include construction machinery​ and other mobile equipment with closed‑circuit drives.

Key specifications and features

• Displacement: 125 cm³/rev​ (size 125).

• Pressure ratings: 400 bar nominal, 450 bar maximum.

• Configuration: Closed circuit, swashplate design, variable displacement.

• Integrated boost/charge pump​ for pilot and control oil supply.

• Two high‑pressure relief valves​ on the high‑pressure side (also serve as charge/boost valves).

• Adjustable pressure cut‑off​ as standard.

• Through‑drive​ capability for mounting an additional pump of the same nominal size.

• Wide range of control options (e.g., HW manual, EP electric proportional, HD hydraulic).

Control and function notes

• The DA control​ is an engine‑speed‑related, hydraulically actuated system: a DA valve core generates a pilot pressure proportional to pump/engine speed. A 3‑position, 4‑way solenoid valve​ directs this pilot pressure to the actuating piston, allowing infinite variation of displacement in both flow directions​ as speed and pressure vary. It provides anti‑stall protection​ by reducing displacement as engine speed drops. This control is intended for specific drive systems and should be validated by Rexroth application engineering.

• The pressure cut‑off (D)​ limits maximum system pressure by reducing displacement to Vg min​ when the set point is reached. It prevents unnecessary high‑pressure relief operation during acceleration/deceleration. As a best practice, set the cut‑off approximately 30 bar below​ the high‑pressure relief valve setting.

Model code breakdown and ordering guidance

• Example breakdown for a similar A4VG125 code: A4VG 125 EP2D1 / 32L – NZF02F001D​

  • A4VG: Series and type (closed‑circuit axial‑piston variable pump).

  • 125: Size (125 cm³/rev).

  • EP2D1: Control device and version (e.g., EP = electric proportional).

  • /32L: Series suffix and mounting flange/through‑drive orientation.

  • NZF02F001D: Further options and design variant details.

• Your exact string (…‑NAF021DT) follows the same coding logic; the final suffix letters/numbers define control options, design variants, and sometimes production configuration. Always match the complete type code​ to your machine’s SIS/parts list and the pump nameplate​ to ensure correct fit and control compatibility. Rexroth offers many A4VG125 variants; verify each field before ordering.

Typical applications and installation tips

• Applications: closed‑circuit hydrostatic drives​ in mobile machinery such as pavers, vibratory rollers, harvesters, coal support carriers, beam transporters, and other construction/port equipment.

• Installation/commissioning checklist:

  • Pre‑fill and bleed​ the closed circuit; verify correct oil type and cleanliness.

  • Check and, if needed, adjust high‑pressure relief​ and pressure cut‑off​ per machine specs; maintain the recommended ≈30 bar​ gap between cut‑off and relief settings.

  • Inspect charge pump​ output, filters, and case drain; ensure through‑drive​ alignment and coupling/shaft end play are within limits.

  • For DA‑controlled​ units, verify solenoid wiring, supply voltage, and that the control logic matches the engine/drive requirements.