fluorescent dye penetrant testing

[sarabande]

another thread, showing how cracks can creep up on you almost unoticed, triggered a train of thought that I could, umm should, really should inspect my 35 yr old ordinary steel shroud plates and stem/stern fittings properly before I paint them.

How difficult is it to use such product as

http://www.magnaflux.com/Products/PenetrantInspection/ZygloFluorescent/WaterBasedPenetrant/ZL4C.aspx

please ?

Are there any standard alternatives or better products ?

 

[VicS]

another thread, showing how cracks can creep up on you almost unoticed, triggered a train of thought that I could, umm should, really should inspect my 35 yr old ordinary steel shroud plates and stem/stern fittings properly before I paint them.

How difficult is it to use such product as

http://www.magnaflux.com/Products/PenetrantInspection/ZygloFluorescent/WaterBasedPenetrant/ZL4C.aspx

please ?

Are there any standard alternatives or better products ?

The snag with that surely that you need the UV light. I have seen dye pen testing done a number of times but always, as for as I can remember, with red dye and a white "developer" sprayed on after cleaning off the surplus dye.
Although Ive never tried it myself it has always looked relatively simple to do.

 

[Eygthene]

We used a similar type of dye penetrant for detecting cracks in metal components. This was done in the laboratory. The parts were first degreased then sprayed with the liquid (must avoid making fingermarks by touching). Then the excess was dried off and the developer (a thin aerosol chalky white coating) was sprayed on. Then in a reasonably dark place, the UV lamp revealed the cracks, by causing the penetrant dye to fluoresce where it was drawn out of the cracks onto the developer.

A violet coloured dye penetrant was also available, used in a similar way, but it was washed off leaving a residue in the cracks, then dried and cracks revealed with the developer. Using this, cracks were readily visible in daylight without the need for UV.

 

[Jcorstorphine]

I have used a similar system but does not need UV lamp. The area under test is sprayed with a red dye and the surplus wiped off. The test piece is then sprayed with a white developer spray which "wicks out" any dye which has penetreted a crack. The cans were supplied by Solent Maintenance and i am sure we bought them through Cromwell.

BTW, The red spray is very very messy so you would need to mask everthing

 

[DaiB]

Crack testing

http://www.elmerwallace.co.uk/Dye-Penetrant-3-Can-Kit/163.htm

£36 for a kit, easy to use.

 

[savageseadog]

I've used the red dye penetrant system on rigging components which worked well. Trickiest bit is the wipe when the surplus dye is wiped off, too much solvent cleans completely including the stuff in the cracks,otherwise easy.

 

[William_H]

Dye penetrant testing of components is a specialised art. The problem being that any lack of skill on your part will give a no cracks result. I think that a very thorough examination with magnifying glass would be just a sensitive to finding cracks. You need to carefully consider where cracks might develop. Most Non Destructive Testing especially on aircraft is where cracks are known to develop.

Of course if you are really concerned then eddy current method might be more sensitive and appropriate.
Eddy current method uses an electronic machine. It is just like a metal detector only used to detect lack of metal. It uses a very small coil about 5mm in diameter. This coil is part of a resonant oscillator circuit. When brought near end on to a known good piece of metal the circuit is adjusted to a steady frequency. The eddy currents form in effect a transformer using the metal as a secondary coil. You now move over the component at a constant spacing. Any crack in the metal will change the resistance of the metal as seen by the coil and so upset (change) the oscillator. (The coil sees the metal as a circle of conductor.)
This method is regularly used for testing the rims of aircraft alloy wheels. Very sensitive and very resistant to operator error.
But again very successful when you know where the cracks may be. good luck olewill

 

[Deleted member 36384]

I would be inclined to use Magnetic Particle Inspection on "ordinary steel" and not Dye Penetrant inspection. This is a specialised service with a trained technician and not really suitable for the untrained. I have been involved in many NDT projects and seen these inspections carried out where it was obvious that the detector identified a crack and also where it was not obvious to me but a crack was picked up by the operator.

If you wish to carry this out just for your own peace of mind then a good inspection with a magnifying glass will be sufficient after any surface coatings have been removed. Do not wire brush and beat the item to death chipping off paint as this can introduce or hide crack like indications which only a trained technician will be able to correctly interpret. If you wish to do this and use the results as evidence for integrity to some 3rd Party then you need to hire the technician. Typically the company will leave with you the inspection sheet and a copy of the inspectors licence. Both will detail the inspection level, type of inspection, material and the qualification of the inspector to perform that inspection type. It is also possible that the inspector can determine if the crack can be removed by grinding out. However, grinding out cracks normally is done to an approved procedure and not just willy nilly. I doubt that your plates have such a procedure available but again, if its for your own peace of mind, a qualified inspector could offer you an opinion.

If you take the shroud plates to a fabrication company they would probably inspect them for you for very little money the next time the inspector was working. Alternatively, contact an NDT company and explain what you want. Dropping them off at the NDT company (if that was practical) could produce a free inspection for just for beer money. It would not take any time at all to do this.