Dye Penetrant Testing and Pre-Cleaning
One of the myths in NDT is that Dye Penetrant Testing is becoming obsolete. Smart phones, GPS’s, Flash drives, HD, voice recognition, Terabyte, Bluetooth, these technology wonders are not fully understood by all of us. For some of us it is even difficult to learn how to use them. But as soon as we can use them it is difficult to go back to using dial phones, paper maps, monochrome screens and writing letters by hand. A lot from what we have used and learnt in the past is being forgotten.
With technology also comes a faster way of doing things. Most of us are not interested in waiting for letters anymore and relay on e-mails. Dictionaries are something of the past as spell checks are taking over that responsibility.
Even in NDT, technology is starting to take over. Phased Array, Tomography and Ultrasonic Testing using EMAT probes are just a few of the latest technologies available.
However, in our high-tech society where many power stations, mines, pulp manufacturing plants etc. are aging rapidly and require fatigue crack detection, can the old NDT method, Dye Penetrant Testing be forgotten? Dye Penetrant Testing still remains one of the most trusted NDT methods on site and still has many advantages over the latest technologies available such as:
- Cost effectiveness.
- Testing on most alloys.
- Ease of training personnel.
- Visually positive.
- Testing of complex geometry parts.
One of the problems with Dye Penetrant Testing in our high tech life styles is the time required to do a good test and because of that, pre-cleaning is the most neglected step in the whole process.
So why pre-clean the part before the inspection? Most of us will say it is to ensure that the discontinuity is not covered in dirt or full of foreign material, thus preventing the penetrant from entering.
Now take a bit of time and ask yourself: why else is pre-cleaning so important?
Here are some other reasons for pre-cleaning parts before inspection.
- Pre-cleaning is mostly performed on site by wire brushing followed by solvent or detergent cleaning. This whole process is done by hand and thus “forces” the technician to do a visual inspection on the part to be tested.
- Pre-cleaning also ensures a better wetting ability on the surface which allows for the penetrant to spread easily over the test surface.