Good day everybody.

The perception about dry powder in Magnetic Particle testing is that it can and may only be used on hot surfaces.

This is not strictly true. You see the very first type of magnetic ink that was developed is the dry powder. Dry powder – because it is dust – has better mobility than wet ink; this means that the powder is able to move to flux leakage sites easier.

And although dry powder costs around R 2000 per kg, it still works out cheaper than aerosol ink.

The amount of ink that goes into an aerosol can is around a teaspoon full with a value of less than R8.

How much do we pay for one can of aerosol magnetic ink? R 80.

That R80 pays for:

The box that carries 10 cans, the can, the white cap, paint on the can, the printed sticker, the paraffin carrier fluid, the propellant to get the ink out of the can, the plastic tube inside the can, the nozzle, the marble and last but not least the printing of the expiry date on the can.

Did I mention that we need to get rid of the empty can afterwards?

Only later was the dry powder mixed with a carrier fluid to make the ink “stick” to vertical and curved surfaces, in those cases the dry powder was just too mobile, it would fall off the test piece.

Dry powder can be carried onto an aircraft without being declared “dangerous goods” and it takes up less space.

We use dry powder on a hot weld, because the white contrast paint – used with the black ink –  turns brown and the paraffin carrier fluid from the ink evaporates immediately when touching the hot surface, resulting in the black ink “sticking to the surface with zero mobility.

Dry powder comes in different colours to contrast with the test surface. And my favourite advantage, dry powder can be collected after use and re-used.

So people, let’s try and save a few bucks here, consider dry powder as an everyday use on flat horizontal, surfaces and let’s use the wet ink on curved and vertical surfaces.

Thanks guys.

Keep up the good work.

Hennie.

Published with the kind permission of Hennie de Wet