Frequently Asked Questions (FAQ)

1. Basic Parameters & Selection

Q: What is the function of this valve?

A: This is a pilot-operated check valve (液压锁). It allows free flow from A1 to A2, but blocks flow from A2 to A1 (zero leakage lock). It can be opened in reverse (A2→A1) by applying a pilot pressure signal. It is designed to lock cylinders or motors in position.

Q: What does "Z2S6A1" mean in the model?

A:

• Z2S: Pilot-operated check valve series.

• 6: NG6 size (CETOP 03).

• A: A-side lock only​ (B-side is free flow).

• 1: 1.5 bar​ cracking pressure (other codes: 2=3bar, 3=6bar).

• 6X: Component series.

Q: What is the difference between Z2S6A1 and a simple check valve?

A: A simple check valve only allows one-way flow. The Z2S6A1 is pilot-operated, meaning it can be "unlocked" remotely via a pilot pressure port to allow reverse flow, which is essential for releasing a locked cylinder under load.

2. Installation & Commissioning

Q: How is this valve mounted?

A: It is a sandwich plate valve. It installs between the directional valve (e.g., a 4WE6 solenoid valve) and the subplate (base plate). Ensure the mounting surface is clean and the bolts are torqued to the specification for NG6 valves.

Q: How do I connect the pilot line?

A: The pilot port (usually labeled X) must be connected to a pressure source that can overcome the backpressure at A2. If the pilot line is blocked, the valve will not open in reverse, causing the cylinder to remain locked.

Q: What are the critical installation warnings?

A:

• Never run the pump dry.​ Fill the housing with clean oil before the first start.

• Pilot Pressure:​ Ensure the pilot pressure is sufficient to open the valve against the load pressure (typically requires ~30-40% of the load pressure).

• Drain Port (if any):​ If your valve has a separate drain port (Y), it must be connected directly to the tank with zero backpressure.

3. Operation & Troubleshooting

Q: The cylinder does not move (remains locked). What is wrong?

A:

1. Insufficient Pilot Pressure:​ Check if the pilot line is connected and the pressure is high enough to open the valve against the load.

2. Blocked Pilot Line:​ Check for closed valves or clogged orifices in the pilot circuit.

3. Mechanical Failure:​ Internal parts (poppet, spring) may be stuck due to contamination.

Q: The cylinder drifts down slowly (does not hold position).

A: This indicates internal leakage.

• Cause 1:​ Worn poppet or seat due to contamination.

• Cause 2:​ Damaged seals on the valve or cylinder.

• Solution:​ Check the valve and cylinder for leaks. Replace the valve if internal leakage exceeds acceptable limits.

Q: The system is very noisy when the valve opens.

A: This is often water hammer (hydraulic shock). It occurs when the pressurized volume is released too quickly. Some Z2S valves have a "pre-opening" feature to dampen this. Consider adding a throttle valve​ in the pilot line to slow down the opening of the check valve.

4. Maintenance

Q: What type of oil and cleanliness are required?

A: Use ISO VG 32/46/68 mineral-based oils (HL, HLP). The oil cleanliness must be NAS Class 9 or cleaner​ (ISO 4406 18/16/13) for long service life. Contamination is the primary cause of valve failure.

Q: Can I repair this valve myself?

A: Not recommended.​ While seal kits are available, rebuilding the precision lapped poppet and seat requires special tools and testing. For critical applications, replacing the valve or using an exchange unit is safer.

Q: What is the expected service life?

A: Under correct conditions (clean oil, proper viscosity, within pressure ratings), the life can be several million cycles. Oil contamination is the primary cause of premature failure.

Disclaimer:​ This data is based on standard Rexroth Z2S series documentation. Always refer to the official datasheet (RE 29019) for your specific application and safety guidelines.