What is NDT? and What methods are used to test welding?

1. Scope

The procedure shall be applied to all radiographic inspection carried out during execution specification of the project material API 5L X60 different size & thickness

2. Purpose

The purpose of this procedure is to ensure that the produced radiographic image is of an acceptable quality and that all radiographic inspection are performed in a safe and controlled manner and conform to project specification and controlling codes.

3. References

• ASME V, article 2
• SNT-TC-1A
• API 1104
• ASTM E 1390
• ASTM E 1079
• ASTM E 94
• ASTM E 797

4. Definitions

         Examiner

        Only personnel who are fully trained and qualified, with adequate experience shall be permitted to undertake radiographic inspection or handle radioactive sources.

5. Procedure

• General:  Gamma ray isotope with focal spot size as follows : ( for Little Welds And Tie – In )

                        Isotope :  Type – IR 192

                       Activity : Up to 60 curie

                       Effective source size : ø 2.7 mm or 2 X 3 mm

                        Half life period  : 74 days

       X-RAY Machine ( for Long Strings have Many Welds)

                 Type of equipment :  Crawler 350 kv

                  Isotope : Type :  Cs 137 (for Control Only)

                    Machine Intensity :  UP to 350 KV

                    Focal spot: 1.5×5 mm

• Pentameters :-

                Wire pentameters type shall be used according to Din  (10-16) .

• Intensifying Screens :-

            Lead PB intensifying screens shall be used “lead thickness 0.1 mm”

•  RT Technique:-

                Radiographic technique shall be DWSI & SWSI.           

                         Radiation Type   Gamma

                         Agfa           D7

                         Kodak        AA400

Equipment

• Isotope radiograph source (IR 192)
• RT device of isotope radiograph
• Lead screen film
• Lead alphabetic letters, numbers and number tape
• Survey-meter
• Cable for RT device (behind & forward)
• Densitometr
• Dosemeter
• Badgefilm 

Radiograph Identification

All radiograph shall contain all data for every film of the weld joint, the radiographic image identification shall include the following information:-

• Project name
• Company name
• Weld no.
• Date of radiograph
• Size of weld joint (diameter & thickness)
• Item no.
• Welder no.

Examination

• Pentameters:
• IQI shall be placed on right angle with the weld being examined close to joint Identification.
• The pentameter shall be present at area of essentially uniform radiographic density.
• Penetrometers should be place at the center for each radiograph.
• 1.4. Where one or more exposure holders/cassettes are used for an exposure, a pentameter image shall appear on each radiograph, except where the source is placed on the axis of the object and the complete circumference is radiographed with a single exposure, in this case at least three equally spaced film side pentameters shall be used.

• Back Scatter Radiation:

As a check on the back scattered radiation, a lead symbol “B” shall be attached to the back of each film holder. If the image of the “B” appears on a darker background of the radiograph, the radiograph shall be unacceptable; a dark image of the “B” on a lighter background is accepted.

• Geometric un-sharpness:

Geometric un-sharpness of the radiograph shall be determined in accordance with the formula as follows:-               

 Ug  =  F  * (T/D)

Ug  =  Geometric un-sharpness

F  = Focal spot size

T  = source object distance.

D  = Distance from source of radiation to weld

** Final acceptance of radiographs shall be based on the ability to see the prescribed pentameter

     image and the specified wire depends on radio graphed weld thickness.

** Geometric un-sharpness of the radiograph shall not exceed the following :-

Item Material thickness (inch) Maximum Ug

1       Under 2″       0.020

2       2″ through 3″          0.030

3       Over 3″ through 4″ 0.040

4       Over 4″         0.070

The examined part could be pipe, sheet, plate or steel structure.

Radiographic density :-

• The transmitted film density of the radiographic image of the body that adjacent to the designated wire of a wire pentameter and the area of interest shall be 1.8 min and 4.0 max for Radiography by gamma ray & 2.0 min and 4 max for X ray.
• Density variation: Generally the density of the radiograph anywhere through the area of interest varies by more than minus 15% or plus 30% from the density adjacent to the designated of a wire pentameter within a minimum /maximum allowable density range specified above.
• Measuring radiographic density by using the densitometer.
• Sensitivity: The accuracy of radiographic image is called sensitivity and the value of it, is Max 2.0%.    

Type of Technique

  General: The types of technique are the method of applicable way to make a radiographic image according to the size, geometric shape of examined objects, the position of object and facility to make       radiographic image.

• Double wall single image and Single wall single image technique shall be used for radiographic inspection when it is practical. 
• Double wall viewing: Applicable techniques for pipe diameter 2″ and less, the radiation passes through two walls and the weld material in both walls are viewed; in this case, the source will be placed away from the centerline of the weld.

Processing of the Film

The instructions relating to the film chemicals concerned should be complied with the processing the film. Film processing shall take place in a darkroom and shall also be air-conditioned to prevent overheating of the process chemicals and be totally lightproof.

The safe lights used during processing shall conform to the requirements of ANSI PH2.22.

• Manual Processing Steps :-
• Remove the shielding lead screen which cover the film.
• The film shall be put in developer path (tank) for 3-5 minutes.
• Stop path by getting out the film from the developer path and put it in fresh water.
• The film shall be put in fixer path after cleaning for 5-10 minutes.
• Washing the film by water after getting the film out the fixer path.
• Washing the film in clean water  for minimum of 4 minutes to ensure remove of resultant chemicals and thus ensuring the correct archival life without detrimental effect .
• Drying the film by forced hot air (dryer) or by heating the film.

• Interpretation

The interpreter must be qualified and certified level II according to ASNT. The interpretation shall be done with respect to the specification of project and acceptance criteria of code.

• Documentation

After making interpretation and evaluation, the result shall be written in the RT report and submitted to client for approval.

6. Safety Requirements

• PURPOSE

The purpose of this procedure is to provide instructions for controlling the use of ionizing radiation sources for radiographic examination. The full requirements of the Site Safety, Health & Environment Plan shall also be complied with when performing non-destructive testing using radiation sources.

• SCOPE

This procedure covers all non-destructive testing activities performed including X-rays and gamma rays from ionizing sources

• REFERENCES

“Radiation Safety For Site Radiography” – Klower Press

“The Ionizing Radiation Regulations 1985” – HMSO (SI 1985 No.1333)

“The Protection Of Persons Against Ionizing Radiation Arising From Any Work Activity” U.K.   

  Health & Safety Executive.

Radiography Operations

General.

• Petrojet will be required to provide Material Data Sheets for each ionizing radiation source. It shall be made available to the Client with a copy provided to the medical centre.
• Data sheets contain, as a minimum, the following information:
• Generic or Trade name and supplier

Chemical name or element name.

• Size and physical properties.
• Current strength and half life of radiation source.
• Storage, packaging and labeling

Work Methods:

• Petrojet will barrier off the area and check to ensure that all personnel have been vacated from inside the barriers, including above and below.
• At the discretion of the Site HSE Supervisor, a wind-out test may be required to ensure that barriers have been erected at a safe distance.
• On completion of the work the Contractor will return the source to its storage area and remove-all barriers and equipment.
• No eating or drinking is allowed within the controlled area.

Personnel Qualify

• Only suitably trained and experienced personnel will be used in radiography work on the pipeline.
• Training records and certificates for all nominated personnel must be available .
• Dose rate records for personnel should be carried forward from past employers.
• All persons in the radiography team must be familiar with site and radiography emergency response procedures.
• All radiographer trained and qualify
• The RT Personal Should Be Qualified And Certified According To ANST Under Practice SNT-TC-1A
• Level II Or III

Vehicles and Equipment

• Radiation monitoring equipment shall be fully calibrated and certified correct prior to and during use.
• Certificates containing source details must be available. These details include the decay table, serial number, type and half life of all radioactive sources to be used on pipeline.
• Advance notice of source transportation, with source container serial numbers and certificates, must be submitted before any movement of sources.
• Monitoring equipment must be calibrated, tested and certified.
• Sufficient barriers and signs are to be available before start of work.
• Defects in equipment must be immediately reported to radiography supervisor for remedial action.
• The work team must have emergency handling equipment.

Medical Arrangements

• All personnel engaged in radiography will be subject to 6-monthly medical examination. Examination results will be available at Petrojet Northern Branch Office, and copies will be held at site
• Film badges are to be worn by all radiography personnel.
• Film badges are to be checked monthly and the results recorded.
• Personal dosimeters are to be used by crewmembers operation.
• Any accidental overexposure to radiation must be immediately reported and medical assistance obtained.

Storage of Isotopes

• Sources will be kept in the approved storage facility at Petrojet yard when not in use.
• Each time a source is moved in or out of the storage facility the source register will be marked accordingly.