Frequently Asked Questions
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.
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
Operation & Troubleshooting
Q: The cylinder does not move (remains locked). What is wrong?
A:
- Insufficient Pilot Pressure: Check if the pilot line is connected and the pressure is high enough to open the valve against the load
- Blocked Pilot Line: Check for closed valves or clogged orifices in the pilot circuit
- 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.
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.
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