When it comes to strict adherence to rules and regulations in the world’s giant sector, one cannot take chances with the functionality of the entire industry. Efficient functioning can only happen when all involved products, materials and equipment are in their best condition.
How do we assess that the materials used for construction or processes are in their best shape?
All this is done with the help of efficient testing – destructive and non-destructive. We have already covered a lot about destructive testing methods.
You might already know a lot about the testing methods used in the oil and gas courses for mechanical engineers.
Here, let’s assess one of the primary non-destructive testing methods, Dye penetrant testing.
What is the Dye Penetrant Test?
Penetrant test, also known as Dye penetrant inspection (DP), or liquid penetrant inspection (LPI), is a widely applied and low-cost inspection method to check surface-related defects such as cracks from fatigue, quenching, and grinding, as well as fractures, porosity, incomplete fusion, and flaws in joints, in all non-porous materials (can be metals, plastics, or ceramics).
What is the basic principle of the Dye Penetrant Test?
The dye Penetrant test helps to locate and determine the severity of surface discontinuities in the material through capillarity. Capillarity or capillary attraction is the ability of a liquid to flow through a narrow passageway (or defect).
What materials are used in the Dye Penetrant Test?
The materials used in the dye Penetrant Test are :
- Dye or liquid Penetrant
- Emulsifying removers or cleaners
These materials are mostly available in liquid or powder form. Most of the time, the materials are available in pressurized spray cans.
We will discuss in detail each of these materials in another blog. The materials used in this test form an important segment in the online course for piping engineering.
What are the steps involved in the Dye Penetrant Test?
The various steps involved in the Dye Penetrant test techniques are –
Surface preparation and pre-cleaning
The test surface is thoroughly cleaned to remove any dirt, paint, oil, grease or any small particle that could hinder the penetrant in absorption in a defect or cause irrelevant or false indications.
The ultimate goal is to have a clean surface where any defects are appropriately open to the surface, dry, and free of contamination.
Application of Penetrant
This is the next step in the process and requires careful implementation.
Penetrants are generally applied to the test surface through spraying, swabbing, and immersion techniques.
The penetrant is allowed “dwell time” to soak into any flaws (varies between 5 to 30 minutes). The dwell time depends on the penetrant being used, the tested material, and the size of defects you prefer to determine.
Removal of excess penetrant
The next step involves the removal of excess penetrant from the surface. The type of penetrant used determines the removal method. The preferable types of penetrant removal methods are – Water-washable, solvent-removable, lipophilic post-emulsifiable, or hydrophilic post-emulsifiable.
Application of developer
In the next step, a white developer is applied to the surface once the excess penetrant is removed. There are different types of developers – dry and wet developers, which we will cover in the upcoming blogs.
The developer’s main task is to draw the penetrant out from defects onto the surface to form a visible indication, commonly known as bleed-out. The bleed-out areas help in determining the location, orientation and possible types of defects on the surface.
Inspection & Post Cleaning
The next step is thorough inspection which is carried out by experienced personnel. As per the specifications, the final interpretation or assessment should be within 10 to 60 min of application of a dry developer or as soon as a wet developer coating is dry.
Once the test results have been recorded, the surface is cleaned again to remove any remnants.
If you are looking for oil and gas training courses online, check our Piping engineering course to understand better.
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.