Non Destructive Testing

NON DESTRUCTIVE TESTING:

NDT testing uses for to access the quality of a component without destructing.
The four principles methods of Non Destructive Testing are mentioned below:
1) Penetrant Testing
2) Magnetic Particle Testing
3) Ultrasonic Testing
4) Radiographic Testing
A good NDT operator has both knowledge and experience, however some of the above techniques are more reliant on these factors.

Liquid Penetrant Testing:
Advantage:
1) Low operator skill level required
2) Used on Non-Ferromagnetic
3) Very cheep cost
4) Simple, easy and cheap to explain or interpreting
Disadvantages:
1) Careful surface preparation
2) Surface breaking flaws only
3) Not used on porous material
4) No permanent record

Magnetic Particle Testing:
Especially used for surface and sub-surface defects in ferrous materials
Advantages:
1) Detect some sub-surface defects
2) Very low cost
3) Simple apparatus or equipment
4) Especially use for thin coatings
Disadvantages:
1) Ferrous materials only
2) Demagnetisation required
3) Direct current flow may cause ARC STRIKES
4) No Permanent Record
5) Must applicable in two directions

Ultrasonic Testing:
Apply to the test surface required: (water, Oil, Grease)

Advantage:
1) Can easily detect lack of sidewall fusion
2) Ferrous and Non-ferrous alloys
3) No Major safety required
4) Portable
5) Able to detect any size of sub-surface defects

Disadvantages:
1) High operator skill required
2) Very expensive
3) Very difficult to interpreting
4) Very difficult for applying

Some Useful Tips about the terms and definitions of Weld and Joints

Weld: A union of materials, produced by heat or pressure

Joint: Configuration of members

Weld Preparation: Preparing a joint to allow access & fusion through the joint faces

Types of weld: Butt, Fillet, Stud, Forge, Seam, Edge, Slot, Flash butt

Types of joint: Butt, T. Lap, Open Corner, Closed corner.

Types of preparation: Bevel’s, V’s, J’s, U’s

Preparation Terms: Bevel angle, Root face, Root gap

Weldment Terms: Weld face, weld root, fusion zone, Weld toes, weld width. Fusion boundary

Weld Sizing (Butt): Design throat thickness, Excess weld metal.

Weld Sizing: (Fillets): Design throat thickness. Actual throat thickness, Excess weld metal, Leg length

Posted by: Zaman