"100% pressure tested" appears on almost every hydraulic valve catalog page. It is also the claim most often untrue. This article explains what per-unit testing actually involves, why it matters more in hydraulics than in most industries, and the four questions that separate a real test program from a line on a brochure.

What happens on a real test bench

A proper valve test is not a pressure gauge and a prayer. The valve is mounted on a test manifold, connected to a power unit, and run through a fixed sequence:

  • Pressure test at rated pressure — and typically a short proof test above it — to verify the casting, seals and machining hold without external leakage.
  • Function test: every spool position is shifted and the port connections verified against the circuit symbol, so a 3C2 is confirmed to actually be a 3C2.
  • Solenoid cycling for solenoid valves — the coil is energized repeatedly to catch early electrical or mechanical failures.
  • Internal leakage measurement against the acceptance limit for that model, which is where worn bores and undersized spools are caught.

The output is a pass/fail record per valve — and just as importantly, a record of the failures. A test program that never fails anything is a test program that is not running.

Why sampling is not enough

Sampling works when defects are batch-uniform. Hydraulic valve defects are not: a burr from one tool change, one bad O-ring from a mixed box, one porous casting in a hundred. A valve that leaks at 315 bar can look identical to a good one on the shelf. Per-unit testing is the only way to catch the individual failures before they reach a customer's machine — where one leaking valve can cost a shift of downtime and a warranty claim across an ocean.

The four questions that expose claims

  • "Show me the test record format." A supplier with a real program can show the per-unit record sheet — test date, pressures, result, inspector. If the answer is a general promise, there is no program.
  • "What happens to failed units?" A real program has a quarantine and rework path. No answer means failures are shipped.
  • "Can I see the bench live?" A five-minute video call to the test bench tells you more than any certificate. A real manufacturer can do this on request.
  • "Will you test to my spec?" Serious buyers test to a standard — ISO 5208-style leakage classes, or their own acceptance limits. A supplier that accepts your limits is a supplier that has a bench, not just a brochure.

How we run it

At VEYDOR, every valve is individually pressure- and function-tested on calibrated benches before it is packed — the same process described on our quality control page, including dimensional inspection, material verification and batch traceability. Inspection records are kept per batch and available on request. Ask us for a test record sample with your next quotation — contact us and judge the program yourself.