WELDING INSPECTOR DUTIES & WELDING INSPECTOR RESPONSIBILITIES

Main keywords for this article are WELDING INSPECTOR DUTIES, WELDING INSPECTOR RESPONSIBILITIES, HYDROGEN CRACKING, welding, HAZ Microstructure, To avoid HAZ Hydrogen cracking.

WELDING INSPECTOR DUTIES & WELDING INSPECTOR RESPONSIBILITIES

The main duties of welding inspector to ensure that all the welding and associated welding actions are carried out in accordance with approved codes, standards and welding procedure or customer specification.

DUTIES OF BEFORE WELDING:-

1) Safety:-

* Be aware of all safety regulations for the workplace.

* Ensure that all operations are carried out in complete compliance with local company or national safety legislation (i.e., permit to work are in place)

* Ensure that safety equipment that will be needed are available and in suitable Conditions.

2) Documentation:-

• Check the specifications in up to the date with latest revision; and equipment.
• Check the drawings are with correct revision numbers.
• Check for approved WPS& its availability.
• Valid certificates of calibration for welding equipment and inspection instruments.
• Check for material & consumable certificates.

3) Materials:-

• Check for its accordance with WPS/Drawings.
• Is in suitable condition and free from damage and contamination.
• Material test certificate is available

4) Welding consumables-

• Check for type, size, condition etc.
• They are specified by the WPS and being stored and controlled as per specification.

5) Welding equipment:-

• There are in suitable condition with valid calibration certificates

6) WPS:-

• Have been approved and available to welders and inspectors.

7) Welders Qualification:-

• Check for the welder whether qualities for WPS and welder qualification Certificate is valid.

8) Weld preparation:-

• Is in accordance with WPS with correct preparation for bevel angles, root face, root gap, root radius, alignment, land and free form conformination.

9) Joint fit ups:-

• Are in accordance with WPS correct bevel and method of preheat applied prior to tack welding. All tack welds are to be monitored and inspected.

10) Preheat (If required)

• Minimum temperature is in accordance with WPS check for its application control and measurement.

 

DUTIES DURING WELDING:-

The presence of welding inspector during welding will almost certainly reduce the no. of weld defects and metallurgical problems which will in turn reduce the overall no. of failures.

1) Site or field welding:-

• Ensure weather condition or suitable and comply with the code.

2) Welding process:-

• Is in accordance with WPS correct welding technique, direction and run sequence is being used

3) Preheat (If required):-

• Minimum temperature is being maintained in accordance with WPS

4) Welding consumables:-

• Are in accordance with WPS and being controlled as per procedure.

5) Welding parameters:-

• Checks for current, voltage, travel speed are in accordance with WPS.

6) Gas flow:-

• Check for the type, pressure flow rate for welding and purging gas for compliance with procedure.

7) Root run:-

• Is visually accepted to code

8) Inter run cleaning:-

• It is to good workmanship standard.

9) Inter pass heating:-

• Maximum temperature is in accordance with WPS.

10) Back gouging:-

• Check for amount gouged, shape, cleanliness is according to approved WPS.

11) Welder:-

• Check the welder is on approval register for WPS being used.

DUTIES AFTER WELDING:-

1) Cleaning:-

• Ensure that the weld has been completely post cleaned.

2) Visual Inspection:-

• Visual inspection is carried out to as certain acceptability of appearance of welds
• Visual inspection of defect like undercut, overlap, surface porosity, incomplete filled groove, arc strike.
• Ensure weld is suitable for all NDT methods

3) Dimensional Survey:-

• Dimensional survey accuracy should be check for its compliance with drawings/code

4) PWHT:-

• Inspect and monitor for compliance with procedure.

5) NDT:-

• Ensure all NDT is complete and reports are available.

6) Repairs:-

• Excavation procedures and welders should be approved.
• Defect area must be marked and complete removal should be monitored by visual inspection and NDT
• Re- welding procedure and welder should be approved.
• Re-welding should be monitored and re – inspected by NDT and visual inspection

7) Pressure:-

• Ensure that & equipment is calibrated.
• Monitor test to ensure compliance with code/procedure.
• Ensure reports are available.

8) Find Documentation Records:-

• Ensure all reports and documents are completed and collected as required.
• Ensure all reports are signed.
• Submission of inspection reports and all relevant document to QA/QC department.

HYDROGEN CRACKING (HICC)

During fabrication by welding, cracks can occur in some type of steel, due to the pressure of hydrogen. The technical name for this type of cracking is “Hydrogen induced cold cracking”.

Hydrogen cracking is also called

1) Cold cracking:-

• Cracking occurs when the weld metal has cooled down

2) HAZ Cracking:-

• Cracks tends to occur mainly in HAZ

3) Delayed cracking:-

• Cracks occur some time after welding has finished (after 48 hrs. or 72 hrs soaking time)

4) Under bead cracking:-

• Cracking occur in the HAZ under beneath a weld bead

Hydrogen Cracking Mechanism:-

Hydrogen enters the molten weld metal when hydrogen containing molecules are broken down into hydrogen atoms during welding. They can diffuse in solid steel and while weld metal is hot they can diffuse to the surface and escape into atmosphere. But at low temperature hydrogen cannot diffuse and if the weldment cools down quick’s to ambient temperature hydrogen will become trapped usually in HAZ.

If the HAZ has susceptible micro structure indicated by being relatively hard and brittle, there are also relatively high tensile stresses in the weldment, and then hydrogen cracking will occur.

Factors influencing susceptibility to hydrogen cracking:-

Hydrogen cracking occur in HAZ when 4 (four) conditions exists at some time.

• Hydrogen is present [above a certain level 15 ml/100 gm of weld metal]
• A tensile stress is acting on the weld. (Above certain level ) more 1/2yield strength
• A susceptible HAZ microstructure is present (Marten site)
• The weldment is at a low temp. (below 300° C )

To avoid HAZ Hydrogen cracking:-

Hydrogen cracking will be avoided by ensuring that at  least on of the 4 factors is not active during welding.

1) Hydrogen:-

• ensure that coated electrodes flux cored wires and SAW fluxes are low in hydrogen when welding
• By using low hydrogen process like TIG, MIG etc.,
• Low hydrogen electrodes must be either backed & stored in a hot holding oven or supplied in vacuum sealed packages.
• Ensure that weld zone is dry and free for oil, grease, rust , and scales
• Check the amount of moisture present in gas.

2) Tensile stress:-

• Avoiding stress concentration due to poor fit up.
• Avoid poor weld profile, sharp weld toes.
• Apply a stress relief after welding.
• Keep weld volume as low as possible

3) Susceptible HAZ Microstructure:-

• Processing steel with a CEV that is at low end.
• Using moderate welding heat input so that weld does not cool quickly
• Apply preheat so that HAZ cools more slowly.
• Maintain inter pass temperature for multi run welds.

4) Weldment at low temperature:-

• Apply a suitable preheat temperature
• Maintain inter pass temperature to avoid welding form cooling down quickly after each pass
• Maintain the preheat temperature ~ 250°C when welding has finished and hold it at same temperature for minimum 2 hrs to facilitate escape of hydrogen.

Main keywords for this article are WELDING INSPECTOR DUTIES, WELDING INSPECTOR RESPONSIBILITIES, HYDROGEN CRACKING, welding, HAZ Microstructure, To avoid HAZ Hydrogen cracking.