NDT & Welding Inspection Techniques

1)Edge Face should be check and equal from every side.
2)“V” Gap or “V” degree that’s size will be in millimeter and usually is 4mm.
3)Joint cleaning should be done.
4)During Tacking should be checked “Porosity”.
5)Arc length should be set in appropriate position. It can be at 6, 5 or 4 mm. If the arc length will not be set at appropriate position it can be cause of welding defects because in the meanwhile oxygen will attack on metal and create defects. So be careful during this process.
6)If porosity find then it should be clear from DPT until correct form later on test will be done again.
7)“V” degree always checked through Gage and it will be provide by Company.
8)“V” degree Pipe design should be “37.5” according to international standards. It can be reduce if water or some thing, which have no pressure that size, can be 35 pye. But for pressure vessels it should be 37.5.
9)Plate size will be according to international standard 30 degree.
10)Welder stamp should be done on base metal and also show his job card.
11)Every thing should be done accordance to Welding Procedures Specifications. And also checked that Electrode is Heat or not.
12)Filling called film, coating called capping.
13)“V” gap size should be 25mm and after welding should be 28mm and capping size should be 3mm.
14)Edge face should be equaled otherwise joint will not be in correct form and welding electrode material will be settle on beginning place that will be cause of “Lack of Fusion”. Because where welding start that current will be 300 and continue but the plate if thin and that current will apply it can be cause of Lack of fusion.

Which type of metal will be use for Foundation?
Ans: Cast Iron will be use for this purpose. Number of quantity of carbon for making it and have no bending ability.

Mild Steel:
Have low carbon and ability to bend and use for (Non pressure pipe lines).

Carbon Steel:
Use for high-pressure lines, i.e. Boilers, Pressure vessels and steam liners.

Remember:
Always use that electrode which type of base metal.
“P” category always use for piping.
Base Metal Welding Material Wire Type
SA516G-70 E7018 ER70S3
P11 E8018 E80SG

How can you check during welding pre heat temperature?
Ans: Temperature Kit. It will be like Tester or Board marker.

What is the difference between Pipe and Tube?
Ans: When we increase the thickness of the pipe then “OD” outer dia will be increase and “ID” will be decrease but when we increase the thickness of tube that “OD” will be decrease and the “ID” will be increase.
Q: Type of Welding Positions.
Ans: 1F: shows that the welding position will be “FLAT”.
2F: Shows that the welding position will be “Horizontal”.
3F: Shows that the welding position will be “Vertical”.
4F: Shows that the welding position will be “Overhead”(only use for Plate)
5F: shows that the welding position will be “use in Pipe”
6G: Use in Plate and Pipe at 45 degree angle.
6GR: Single, Use of Square tank Only.
Q: What is HAZ?
Ans; HAZ means Heat Affected Zone. During welding when contamination attacks on the weld zone then shielding gases stopped them, because of this a line generated on both sides of welding area. Which call HAZ.
Q: What are the causes of Porosity?Ans: 1) Your hand is not stable.
2) Welding electrode using date has expired.
3) During loading and Unloading Electrode has damaged.
4) Iron has large quantity of humidity.

How can you define Electrode Number?
Ans: Example: E-7018
E: Stands European
70: Stands Tensile: 70x 1000= 70000 Tensile
1: Shows welding position
8: Electrode material specifications
What is Root?
Ans: It is base of the base metal and welding material. It always shows inside of the metal.
What is Capping?
Ans: After completing root, will do capping.
What is Excess of Penetration?
Ans: It always shows inside of the metal on welding zone.

Note: Always consider your welding level than welding position. Concentrate on your hand position.

Arc length always should be 5mm melting point and weld metal.

Causes of porosity:
Loading and unloading, Break, Cause porosity
If the base metal will be rusty, that will be cause of porosity.
As you know that rust generate because of humidity. There is large quantity of humidity consist in air, and air is cause of rust.

Q: How we can check Porosity?
Ans: If it is consist on Surface that can find through DPT and also check through RT, UT and Mechanical Test.
Q: Why we do perform Mechanical Test?
Ans: If the current Requirement was 100 Amperes and it applied during welding 90 Amperes, which will be cause of defects because weld metal and base metal will not be mixed at appropriate level. And when you apply chisel test they will break into different pieces not in one piece and will be thick.
II) If the current requirement is 100 Amperes and was apply during welding 110 Amperes, it will be cause of heat that cause of weakness.
III) Under cut reduce the using period.

Types of Tests:
Butt Joint: All tests will be applicable, RT, UT, DPT, MPT, Mechanical Test.
T Joint: Only DPT will be applicable because it always install in Wall.
Corner Joint; DPT will be applicable.
Edge Ends: DPT
Fillet Joint: Only use for Tank Bottom (Kerosene Oil will be applicable)
Lap Joint; Vacuum Test will be applicable.
Some Important Test:
Hammering Test: It is use for testing strength of welding material. Firstly, we apply chisel on the welding zone and break them suddenly, if it break straight that welding material melt in correct form.
(II) If the ripples will be in straight form and not rise in surface that will be current equaled, otherwise it will be rise on metal surface that shows current is too high.
Remember: In auto mobile industry we see Alloy Wheel Rims. You know that there is big difference between of both wheels of wait.
Front wheel always light than back wheel. It has 3 to 4 kg difference. It make through forging process. There are two different types dyes one male, second female and always use oil around wheel cap so that will not paste with dye. Then 45000 kg load apply on that specific metal and cut inside and make it in a good shape. Then, transfer to CNC machining centre and make it in a good form.


Published & Posted by: ADNAN ASHRAF