Frequently Asked Questions
What does EO2 (electro-proportional displacement) control do?
EO2 varies the pump's swash plate angle - and therefore output flow - in proportion to an external electrical command signal (typically ±10 V, 4-20 mA, or PWM via external amplifier). The pump has an onboard LVDT position feedback. EO2 requires a higher pilot pressure (min. ~50-100 bar for Size 250) vs EO1 (~20 bar). It provides no pressure limiting - a separate system relief valve is mandatory.
What is the difference between EO2 and EO1?
Both are electric proportional displacement controls with LVDT feedback. Main difference is pilot pressure requirement:
- EO1: Min. pilot ~20 bar (Sizes 40-250)
- EO2: Min. pilot ~50-100 bar (Sizes 250/355/500+, offers higher control stiffness)
If replacing EO1 with EO2, ensure your system can supply adequate pilot pressure.
Can I mount a second pump on the back?
Yes. The PPB code = through-drive capable. An A4VSO (same/smaller) or gear pump can be flange-mounted to the rear. N00 = no auxiliary pump pre-fitted, through-drive shaft present.
What are critical installation requirements?
- Case Drain: Plumb directly to tank, backpressure ≤ 1.5-2 bar. Never tee into main return
- Suction Line: Short & large-diameter; absolute inlet pressure ≥ 0.8 bar. Use 100 µm suction strainer
- Pilot Pressure (EO2): Supply pilot port with clean oil ≥ specified min. (typically 50-100 bar). Insufficient pilot → swash plate won't stroke
- Rotation Check: "L" = counter-clockwise from shaft end - verify prime mover direction before coupling
- Bleed: Fill case and suction with oil, vent before first start-up
Does EO2 need a separate amplifier?
Yes. Pump has solenoid + LVDT but requires an external proportional amplifier (e.g. Rexroth VT 5035-1X or PLC analog output with current driver). Amplifier ordered separately.
Is a system relief valve still required?
Yes, absolutely. EO2 controls flow/displacement only - install a properly sized system safety relief valve (e.g. DB type) set above max working pressure + ~10-15% margin.
What oil cleanliness is required?
Maintain ISO 4406 18/16/13 (NAS 1638 Class 8-9) minimum using return-line filter β₁₀ ≥ 200 (10 µm nominal). Contamination is the #1 cause of A4VSO premature wear.
Is this the main pump for a wheel loader or excavator?
No. A4VSO is an industrial open-circuit pump. Mobile wheel loaders and excavators typically use A4VG (closed circuit), A11VO (open axial), or A2FO (fixed) as travel/main pumps. A4VSO may be used on loader/excavator factory test benches or auxiliary stationary HPUs, not as a direct OEM travel pump replacement.
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