Cracks or defects on some surfaces can be a serious problem. If you manufacture parts that have to be intact for safety reasons, then you might need to run testing processes on them before you sell them. Or, you might test parts periodically while they are in use to ensure that they are in the right condition.
Penetrant testing is a good way to find flaws fast. During this testing process, you apply a penetrating liquid to a surface. If the surface has any damage, the liquid shows you exactly where it is.
However, you do have multiple choices to make before you choose the right penetrant. What do you need to know?
1. Penetrants Can Be Fluorescent or Colored
Liquid penetrants come in two types. You can choose to use a fluorescent or colored solution. You apply both solutions in the same way by painting or spraying them onto a surface. However, you read their results differently.
Fluorescent penetrants aren't visible. You view them under ultraviolet light in the dark. So, you will need a fluorescent scanner to make an inspection. When you run the scanner over the surface, you will see fluorescence in cracks, holes, or defects.
Colored solutions are visible. Once you apply the penetrant, it will change color if it seeps into a defect. You won't need a scanner or to work in darkened conditions.
2. Penetrants Have Different Cleaning Requirements
Once you've applied a penetrant, you need to clean it off before checking for defects. You're looking to see if any of the liquid has seeped into a crack or hole. This liquid will stay in place after you remove the rest of the coating.
You can use water to clean off some penetrants. However, some products will only wash off if you use a solution that contains a special detergent or chemical.
Water-cleanable products are faster, cheaper, and easier to use. However, in some cases, water isn't the best cleaning solution. For example, if water will degrade the penetrant, then you won't get accurate results. Here, you need to use a cleaning substance that leaves a penetrant inside a defect so that you can see it.
3. Penetrants Have Different Sensitivities
While penetrants all have the ability to find flaws in a surface, they have different sensitivities. You need to find a product that is sensitive enough to find defects at the right level for your inspection requirements.
If you simply need to check for significant cracks or holes, then you can use a less sensitive penetrant. However, if you need to find even the smallest flaw for safety reasons, then you should use a more responsive product with higher sensitivity ratings.
To find the best penetrant for your testing needs, ask non-destructive testing suppliers for advice. For more information on fluorescent penetrant inspection, contact a professional near you.