Dye penetrant test is a type of visual inspection for the detection of surface flaws and discontinuities. In one of the earlier blogs, we discussed the various processes and materials involved in the test.
We all know that penetrants are the key detecting elements that help in successful flaw detection. Here, we will discuss the type of penetrants used in dye penetrant tests.
This is an essential topic in the oil and gas courses for mechanical engineers.
Penetrants in Dye penetrant test
Considering the advantages of Dye penetrant testing, let’s see how penetrants help in effective flaw detection.
- It produces a flaw indication that appears much larger than the actual flaw. This helps in detecting even the smallest of flaws.
- Penetrants provide a high level of contrast between the indication and the background that helps in the appearance of the discontinuity much easier.
Now, let’s see the type of penetrants used in dye penetrant testing. You must gain in-depth knowledge about the crucial topics in the online course for piping engineering.
Penetrant types – Basic
Fluorescent Penetrants – They contain a dye or mixture of dyes that fluoresce when exposed to UV light. These penetrants are effective in flaw detection in the parts used in aeroplanes, helicopters, automobiles, and medical facilities.
Visible Penetrants – Visible penetrants contain a red dye that provides high contrast against the white developer background. You must remember that visible penetrants do not require any darkened area and ultraviolet light for flaw detection.
Penetrant types based on the method of excess penetrant removal
Water washable – Water washable penetrants can be removed from the part by just rinsing with water. These penetrants contain an emulsifying agent (detergent) that helps wash away the penetrant from the part surface just with water. These are also known as self-emulsifying penetrants.
Post-emulsifiable – When removal of the penetrant from the defect due to over-washing of the part is a concern, a post-emulsifiable penetrant can be used. Post-emulsifiable penetrants require a separate emulsifier to break down the penetrant and make it water washable.
Solvent removable – Solvent removable penetrants use a solvent to remove excess penetrants from test article surfaces. Examples of solvent removers include methylene chloride, isopropyl alcohol, naphtha, mineral spirits, etc.
Apart from these, there are some penetrants used to detect microscopic and tight fatigue cracks. Here, penetrants are chosen based on strength or detectability of the indication.
The penetrants are used as per the sensitivity level, which are:
- Level ½ – Ultra Low Sensitivity
- Level 1 – Low Sensitivity
- Level 2 – Medium Sensitivity
- Level 3 – High Sensitivity
- Level 4 – Ultra-High Sensitivity
The brightness of the indication produced is then measured using a photometer.
This was all about the type of penetrants used in the flaw detection in the dye penetrant test. The penetrant types is a crucial topic in the oil and gas training courses online. To know more about all the processes and materials in the oil and gas industry, check our course or blog section for interesting topics.
by Debashree P
Debashree is an Aeronautical engineer by education and a curious researcher by passion. She is passionate about engineering and technology. She is an avid technology writer who has a knack for developing content for websites, newsletters, blogs, articles, advertising and marketing materials based on the requirements. Technologies of her interest include Aviation, Oil & Gas and AI.