A little
technical stuff for today’s post, specifically aimed at engineers involved in
the core sector of quality control.
Dye
penetration test or DPT as it is popularly referred to in the industry is a
basic test aimed at the detection of surface faults of machined surfaces viz.
cracks, porous formation and flux deposit.
The
test is carried out using a DPT kit which consists of:
1. Cleaner:
A transparent fluid used to clean the test surface and is the same as in paint
thinner.
2. Penetrant:
A red fluid applied on the surface and as its name suggests penetrates into the
surface faults.
3. Developer:
White in color, this fluid points out the surface fault; points on which
correction is needed.
The
test in itself is a easy 4 step procedure which is quick and provides for a
quick surface check. However, microscopic faults are not addressed by this
procedure and different methods are suggested for them. The steps to e carried
out to conduct the DP Test are:
1. Clean
the intended surface with a soft cloth so as to remove all dust and grime and
then apply a layer of the cleaner.
2. Wipe
off the cleaner with a cloth and then apply the penetrant on the surface. Let
the penetrant to be on the surface for at-least 1 minute.
3. Wipe
the penetrant off the surface and apply the cleaner again to remove all visible
traces of the penetrant by wiping.
4. Apply
a thin layer of the developer onto the surface. Coloring of the developer at
various points suggest the faults.
It
is usually assumed that points of red are usually pin holes or porosity whereas
long continuous traces are either cracks or flux deposits.
However do remember that greater amount of developer may be applied to cheat the test as the penetrat fails to show up on the surface. If there is a doubt, scrape off a little of the developer film to check for any penetrant traces or conduct the test again.
