Oscillating Tube Basics: Setting Up IPX3 and IPX4 Sprays

The oscillating tube is the workhorse of the middle of the IP water ladder. IPX3 and IPX4 look nearly identical on the bench, same tube, same spray nozzles, same ten-minute clock. The difference lives in the swing, and labs that treat the two as the same test produce reports that a strict customer will reject.

The swing is the standard

For IPX3 the tube swings through a limited arc, about 60 degrees either side of vertical, so the spray sweeps the surfaces that splashing water would reach. For IPX4 the tube swings through a full circle, splashing from every direction including from below. Same tube, same nozzles, different sweep, different claim. Products rated IPX4 have to prove their gaskets from below, which is why under-body seals fail IPX4 after passing IPX3.

Flow per nozzle and the ten-minute clock

Each nozzle's flow is set so the total matches the standard for the tube size and the number of open holes facing the sample. In practice the flow per hole lands near 0.4 L/min for IPX3-type setups, with the balance of the pressure and angle doing the rest. The standard duration is ten minutes, enough time for the sweep to cover every surface, and the sample sits at its normal mounting position or rotates on the turntable at the centre of the tube.

Small details that change the verdict

Balance the tube's flow by counting the open nozzles facing the sample, since a tube with half its holes plugged changes the real intensity even when the pump gauge looks right. Verify the sweep angle with the tube running, not from a scale painted on the frame. And photograph the sample in position before starting, because "centred in the tube" means different things to different operators, and the photo ends the discussion.