Nozzle Calibration: The Number That Decides the Test

The jet nozzles used for IPX5 and IPX6 are precision parts, and they wear. A nozzle that has eroded from 6.3 mm to 6.5 mm delivers noticeably more water at the same pressure and produces a test that is harsher than specified, or a flow that no longer matches the gauge reading.

What to check

Bore diameter with a pin gauge or callipers, flow rate with a bucket and stopwatch, and pressure at the nozzle with a calibrated gauge. Check the spray pattern visually: a worn nozzle produces an asymmetric jet with visible streaks.

Frequency

Before every certification test, and at least quarterly in a busy laboratory. Replace nozzles rather than reaming them; a reworked nozzle no longer matches the standard.

Record keeping

Log the flow at a reference pressure each time. A gradual decrease indicates a partial blockage from scale; a gradual increase indicates wear. Both are visible in the log long before they affect a test result, which is the point of keeping it.

Pressure gauge placement

Measure at the nozzle, not at the pump. The pressure drop along the hose is significant at 100 litres per minute, and a gauge at the pump will read high, leading the operator to reduce the actual jet pressure below the specified value.

Related technical notes

• The Spray Nozzle Alternative for IPX3 and IPX4
• IP54 or IP65: Reading Both Digits Together
• What an IP Test Report Must Contain