TYPE OF NON DESTRUCTIVE EXAMINATION
Friends today we discussed the type of non destructive examination method for find out the imperfection in weld joint and what method is suitable or appropriate for particular testing. Before it we discussed about weld imperfection.
Weld imperfection is that impurities that impart in weld joint during welding by one of the following reasons.
- Improper current and voltage.
- Improper welding speed.
- Electrode condition is worse or not baked.
- Lack of welder skill.
- Welding position is not correct.
- Lack of cleaning of weld during each pass.
- Magnetic arc below.
- Misalignment of fit up of joint.
We can find out these impurities by one of non destructive method and also we know that by using particular method we can find the particular types of impurities .these methods are given below.
- Visual testing – this type of testing occur by naked eye or we can find out the imperfection in weld which can we see by our eye called visual testing. By use of this testing we can find out the imperfection such as undercut, porosity, root concavity, inadequate reinforcement, misalignment, arc strike and burn through.
- Penetrate testing - other name is dye penetrate testing. In this method we use three type of liquid cleaner, penetrate and developer. First we clean the surface then applies penetrate. Allow the liquid to penetrate in imperfections for some time and apply developer. Then developer sucks that penetration and we find out the imperfection. By this method we find out imperfection such as cracks, porosity, over lap and incomplete penetration.
- Magnetic testing - this type of testing done by creating magnetic field and magnetic particle. That particle collected on that point where impurity exists. By the use of this method we can find out the flaw such as cracks, incomplete penetration and overlap.
- Radiography tests - it is very useful and common testing method that can be used in many fault detection such as porosity, slag inclusion, incomplete fusion, incomplete penetration, root concavity and burn through.
- Ultrasonic testing- this is called UT and this is very accurate and mostly used in process plant for find out the thickness of pressure vessels and in weld imperfection it is used in find out incomplete penetration and fusion.
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