Turntable Speed in IP Testing: Why 1 rpm Matters

Most IP water tests place the sample on a turntable rotating at 1 revolution per minute. The speed is not arbitrary: it sets how long any given point on the enclosure stays in the jet.

Why 1 rpm

At 1 rpm a full revolution takes 60 seconds, so a jet that covers a narrow band exposes each point for a predictable fraction of the test. Doubling the speed halves the water delivered per unit area at any point, which is why a fast table produces optimistic results.

Exceptions

IPX9K specifies 5 rpm, because the four fixed jet angles need the sample to present all sides quickly. Some product standards modify the speed or dispense with rotation for large fixed installations, where the nozzle is moved around the enclosure instead. Always check the product standard, which takes precedence over the generic method.

Checking the table

Time one revolution with a stopwatch, loaded with the sample, not empty. A table that runs at 1 rpm unloaded can drop to 0.7 rpm under an off-centre load. Also check that the sample is centred: an off-centre sample swings through a larger arc and sees more water on one side.

Related technical notes

• IPX4 or IPX5: Choosing the Right Water Level
• Preconditioning Before an IP Test: The Step Everyone Skips
• IP Rating and NEMA Type: Mapping Two Different Systems