Liquid penetrant testing was discovered in 1940s to detect flaws on the surface of materials. Although the processes have evolved over the years the basic principles still remain the same. |
What is a liquid penetrant testing?
It is a non-destructive test method to develop the samples being inspected. The test is truly helpful in detecting porosity, cracks, fracture or any other flaws. Their usage is basically on machined, welded and other manufactured products. They can be very easily used in non – porous and smoother materials such as plastics, glass and fire ceramics too.
The test goes truly with its name as the penetrants are the samples used during testing in order to visualize flaws. But their selection is based on the sensitivity of the test and other factors which includes the different equipments being used and the test site. They are available in 2 different categories based on their colors- visible dye and fluorescent dye. The latter is also available in different sensitivities.
Penetrants are also washable with water, removable with a solvent or through an emulsifier. They can be hydrophilic and lipophilic.
How does the process work?
The testing processes can be broken down into distinct steps:
1. The first process is pre-cleaning which involves through surface cleaning. This process is to test samples of grease, heat treat cycle, paint and plating. Generally we use solvent for this process. The test sample may require other procedures like steam, vapor, chemical and ultrasonic cleaning.
2. The nest process is Penetrant application where the dyes are applied using spraying, brushing or immersing. The choice of this is based on the shape and size of the test piece. The total time the sample is soaked is called the penetrant dwell time. The surface finish, temperature and type of material require dwell time. Based on the test specifications you work out on the dwell time and the application.
3. After the dwell time has elapsed the excess liquid is drained off. Excess dye can easily washed through water. But you should never directly rinse through water, you should use an emulsifier at first. During this procedure try to lower down the temperature and let the sample dry out before the next application.
4. Further we apply the developer which allows the penetrant caught in the sample in being removed. Developers may be applied using a dry powder or a spraying wet developer. This is a important process in the inspection step.
5. Further the inspection is carried out visually by inspectors. The use of UV light or lamp is used during this step. The sample will be accepted or rejected based on specifications or acceptance criteria.
6. Post cleaning the process involves thorough cleaning to remove any residues.
Magmatic Online are one of the experienced technocrats with years of experience in NDT. The processes are tech savvy and they help customers with innovative techniques to help in their processes. They are a trusted partner for these inspection in different commodities which include accessories, consumable services etc. They are the tech savvy partners you look forward to for all your inspection services.
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