Crack penetrating / detection dyes?

[Anthony]

Hi, rebuilding an engine and want to check for cracks in the block (as it sat for sometime with water in some cylinders during a winter), so am trying to source the kind of dye that penetrates into cracks then shows them up, I understand that there are both UV ones, and types that require a developer.

Which is better for a cast iron block, and where can they be obtained from in the UK? I have googled but all I can find is general info on them, no UK retail / mail order places.

Is there a particular brand that is better than an other, are they difficult to get good results with etc? Any other tips appreciated.

Thanks

Ants

 

[earlybird]

Try googling Ardrox and/or NDT products. Hope this helps, though might not be cheap.

 

[VicS]

Kit of 3 aerosols. cleaner, red dye and developer available here for a bit over £50

http://www.lawson-his.co.uk/scripts/prod...etrant%20System

Sure there must be plenty of other places too. Ever heard of Google. Stick in Dye penetrant and see what comes up.

Yes there are fluorescent dyes but you need a UV light to use those. All I have ever seen used is the red one as above.

 

[DownWest]

It might be easier to pressure test the block. I used to use dye check on aircraft, but only to confirm what I thought I could see. ie scratch or crack. Frost damage should be visible.
A

 

[vyv_cox]

Dye penetrant is what you are looking for. UV takes a bit more skill and you would need a UV light source, which will cost you more.

You need first to remove any grease from the block, petrol should do this well enough or you can use the stuff sold for the purpose. You then spray the area to be checked with the dye, which is a very strong red colour. Leave a minute or so, then wipe off with paper towels. Then spray the developer on, which is a titanium dioxide powder in suspension. The dye that has crept into any cracks will be drawn out and show up as a red line. Like this, the line running downwards.

You need to be a little bit careful with cast iron as the graphite tends to draw in some red dye, so don't assume the block to be porous.


Rocol is a well known company in this field. It will cost you £47 for a kit of one each of cleaning solvent, dye and developer.

 

[Anthony]

[ QUOTE ]
Ever heard of Google. Stick in Dye penetrant and see what comes up.

[/ QUOTE ]

As mentioned, I did try googling but only found general info, nothing retail / mailorder.

Thanks for all the tips, sounds like the 3 pot method is the way to go. Unfortunatley I cant pressure test it as there was some corrosion to the cylinder walls so I will be honing them out first now that I have the head off. If I had forced it to turn over with the corrosion in it would likley have scored / siezed. Whilst I have it apart I want to check for cracks before spending lots of parts to rebuild it only to find that the block is damadged.

Many thanks!

Anthony

 

[William_H]

Dye penetrant crack detection is the most common crack detection method for aluminium engine blocks on (piston ) engines on aircraft. As said it can be used with the developer powder or the UV light detection method.
It takes much hands on practice to get a useful test. If you do it repeatedly on the same kind of engine block you get used to indications that are significant and disregard the spurious indications of surface defects.
IMHO your chances of doing a once off inspection successfully is fairly slim. But if it gives you confidence then go ahead. Eyeball crack inspection is still the primary tool for what you want.

However for cast iron crank shafts etc Magnetic particle inspection is the most common. Here the component is placed in a very strong magnetic field. A wash of oil with finely divided iron particles with a UV flourescent additive floods the part to be inspected. Any discontinuity in the iron causes the iron particles to line up on each side of the crack. These are then detected with the UV light. This method can detect cracks to a reasonable depth.
There are other methods of mag particle detection using a plastic polymer with iron particles where the plastic is molded around the area while in mag field. Thhe mold when removed will show signs of the iron particles migrating to the crack area.
NDT is a very specialised area which really works best if you know where a crack is going to occur. It is not so useful for a general inspection. It really is only useful for high value and criticality items.
I think you might best forget it and just do a careful hand glass inspection of possible problem areas.
If you want further advice and supply of products go to a nearby light aircraft field with maintenance facilities.
good luck olewill

 

[DaiB]

Finding a crack gets harder the rougher the surface using dye penetrant. However
before the magic 3 cans came along there was another way, but best on machined surfaces, e.g. liner walls.
Get yourself some parraffin/avgas/kero lower the S.G. normally the better, mix in a small amount of old black engine oil.
Preclean the surface as best you can and then pour over the mixture.
Wipe off excess so surface is dry.
Sprinkle with fine chalk powder/talc. The fluid left in the crack will show up as a line as it soaks up the chalk.
This is how we did it at sea before the 3 can stuff came along.
Can 1 is a cleaner similar to electroclean.
Can 2 is a red fluid of low surface tension.
Can 3 is a developer with similar properties to talc/chalk.