R900476838 Z2FS6-5-4X/2QV German Rexroth dual one-way throttle valve

FAQ — Frequently Asked Questions

Q1: What does "2QV" mean in the model number?

A:​ "2Q"​ means both ports A and B are equipped with throttle/check combinations for main flow limitation (used between directional valve and subplate). "V"​ indicates FKM (Viton®) seals, making this version suitable for HFC water-glycol or HFD phosphate-ester fluids — unlike the standard NBR-sealed version which is for mineral oil only.

Q2: How should this sandwich valve be installed in the stack?

A:​ The Z2FS6 is installed directly between a directional control valve (NG6/D03) and its mounting subplate or manifold. The throttle side (A₁→A₂, B₁→B₂) faces the directional valve; the free-flow (check) side faces the actuator. Ensure port alignment matches ISO 4401-03 and tighten the M5 bolts with even torque (~8–10 Nm in cross pattern).

Q3: Which direction is throttled and which is free-flow?

A:​ Flow from the directional valve side (A₁/B₁) to the actuator side (A₂/B₂)​ passes through the adjustable throttle orifice. The reverse flow (A₂/B₂ → A₁/B₁)​ lifts the check valve seat and returns unrestricted (free flow). If you need inlet throttling vs. return throttling, mount the valve accordingly in the stack.

Q4: Why does cylinder speed seem unstable or the valve "clog"?

A:​ The most common cause is oil contamination​ blocking the tiny throttle gap — always maintain ISO 4406 20/18/15 cleanliness and use a 10 µm return-line filter. Also verify the lock nut is not over-tightened​ (which can shift the spindle setting) and that system pressure is sufficient — very low differential pressure across the orifice can make flow less repeatable.

Q5: Can I use this valve for pilot flow (switching time) adjustment?

A:​ The "2Q" version​ is intended for main flow limitation (actuator speed control). For pilot flow limitation (adjusting pilot-operated directional valve switching time), a "1Q" version​ (throttling only one pilot line) would normally be used, though a 2Q can physically work in some pilot circuits. Match the version to your application requirement.