API 570 EXAM STUDY GUIDE [MODULE 6 : PART 2] ASME SECTION V RADIOGRAPHIC EXAMINATION

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ASME BPVC SECTION V : ARTICLE 2 RADIOGRPAHIC EXAMINATION

As per the BOK of API 570 piping inspector exam,
The inspector should be familiar with & understand
a) The scope of Article 2 & General requirements
b) The rules for radiography as typically applied on both welded seams such as, but are not limited to 

  • Required Marking
  • Type, Selection, number & Placement of IQI's
  • Allowable density and density ranges
  • Control of Backscatter radiation
c) Records
Those points which contains "Shall" need to be noted as they are mandatory requirements as per code. The condition of "Shall" can be seen in all ASME codes. As those Mandatory requirements are to be complied during the excution of job by a API 570 Piping Inspector, from the exam point of view and on job requirement point of view those points are to be remembered. Underline the "Shall" in your code book and revise it.

T-210 Scope: 

  • Radiographic examination of 
  1. materials including castings 
  2. welds.

T-221 Procedure Requirements:

  • The radiography examination shall be performed in accordance with a written procedure.
  • Each procedure shall include atleast the following information
      •  material type and thickness range
      • isotope or maximum X-ray voltage used
      • D=source-to-object distance
      • d=distance from source side of object to film
      • F=source size
      • film brand and designation
      • screens used
Procedure demonstration for Density and IQI requirements are required. Procedure demonstration can be done on production or technique radiographs.
T-222: Surface Preparation
1. Materials Including Castings: 
Surface preparation as per referencing code requirement
2. Welds:
The weld ripples or weld surface irregularities on both the inside (where accessible) and outside shall be removed by any suitable process to such a degree that the images of surface irregularities cannot mask or be confused with the image of any discontinuity on the resulting radiograph.
The finished surface of all butt-welded joints may be flush with the base material or may have reasonably uniform crowns, with reinforcement not to exceed that specified in the referencing Code Section.
Note these points:
Weld ripples shall be removed. 
By which Process? By a Suitable Process
Inside and Outside weld ripples shall be removed
If inside is inaccessible? It is mentioned that 'where accessible' it is to be removed.
To what degree it is to be removed? Such that the surface irregularities cannot mask or be confused with the image of any discontinuity on the resulting radiograph. 
Is it required that the butt welds are to be flush with the base material? The butt weld joints may be flush with the base material or the reinforcement is allowed within the limit of referencing code with reasonably uniform crowns.
Any Reinforcement limitation as per this code? No reinforcement limits are to be as per referencing code.
The weld reinforcement is a factor in the selection of IQI. So whether the surface of weld is flush with the base material or the availability of reinforcement as per referencing code is an important factor.

T-223 BACKSCATTER RADIATION

A lead symbol “B,” with minimum dimensions of 1/2 in. (13 mm) in height and 1/16 in. (1.5 mm) in thickness, shall be attached to the back of each film holder during each exposure to determine if backscatter radiation is exposing the film.
Note these points:
'B' to be placed on back of each film holder.
Where it is to be placed on the film holder? Back of the film holder.
Is it acceptable to keep it for one exposure of a joint? NO, It is needed for each exposure and back of each film holder.

T-284: Excessive Backscatter

The topic of backscatter will be complete if we discuss T-284 also. 
  • Light Image of 'B' on darker background of radiograph - Not acceptable
  • Dark Image of 'B' on a lighter background of radiograph - Not cause for rejection
Note these points:
This can be remembered in this way. 'B' relates to Black. If 'B' is Black it is acceptable, if not rejectable.

 T-224 SYSTEM OF IDENTIFICATION

A system shall be used to produce permanent identification on each radiograph traceable to,
  • the contract,
  • the component,
  • weld or weld seam, or part numbers, as appropriate.
  • the organization’s symbol or name
  • the date of the radiograph
These identifications shall be plainly and permanently included on the radiograph. This identification system does not necessarily require that the information appear as radiographic images and do not obscure the area of interest.
Note these points:
Identification on a radiograph:
The contract - The work order number or some naming convention for identification as agreed by client/PMC and Contractor will serve the purpose.
Instead of component and part numbers, The isometric line number and the joint number will serve the purpose
Instead of Organisations symbol, short form of organisations name or some related naming convention can serve the purpose as agreed between client/PMC and contractor.
It is a common practice to set all the above mentioned information in Lead Letters and keep it in front of the film holder so that all those information appears as images in the radiograph along with weld joint. The code is not making it mandatory to appear all these as permanent images. But for the easiness of identity and to avoid errors practically all these information's are set as radiography images. 

T-225 Monitoring density limitations of radiographs.

Film density is to be judged by either a densitometer or step wedge comparison film.
This will be discussed in detail in T-262.

 T-226 Extent of Examination

The extent of radiographic examination shall be as specified by the referencing Code Section.

T-231 FILM

Industrial radiography film to be used.
SE-94: Standard guide for radiographic examination
SE-999: Standard Guide for Controlling the Quality of Industrial Radiographic Film Processing

T-232 INTENSIFYING SCREENS

Intensifying screens may be used when performing radiographic examination in accordance with this Article.

T-233 IQI design

IQI shall be either hole type or wire type
Hole type: SE-1025 reference standard
Wire type: Se-747 reference standard
ASME wire type IQI’s are available in 4 sets. Set A, Set B, Set C and Set D.
ASME hole type IQI’s are available in 23 IQI designation numbers each consist of a thickness as per this code and contains 3 holes designated as 1T, 2T and 4T
Alternate IQI design: IQI's designed and manufactured in accordance with other national or international standards (DIN standard, ISO standard etc) may be used provided the essential wire diameter as per this code should be able to meet by that IQI. A wire diameter lesser than the essential wire diameter is also acceptable.
 Equivalent IQI Sensitivity (EPS) is equal to or better than the required standard hole-type IQI.
Note these points:
Two types of IQI's are available, Wire type and hole type 
Wire IQI designation based on this code consists of 4 sets and each set contain 6 wires.
In each set the most thicker wire will be on the right side.
Alternate IQI's can be used. A wire diameter lesser than the essential wire diameter, if available, is also acceptable while selecting an alternate IQI set.

T-234 Facilities for viewing of radiographs.

Viewing facilities shall provide subdued background lighting of an intensity that will not cause reflections, shadows, or glare on the radiograph that interfere with the interpretation process.
Equipment used to view radiographs for interpretation shall provide a variable light source sufficient for the essential IQI hole or designated wire to be visible for the specified density range.
The viewing conditions shall be such that light from around the outer edge of the radiograph or coming through low density portions of the radiograph does not interfere with interpretation.
Note these points:
The radiography film viewer should have a facility to adjust the light intensity
How much light is needed for viewing a radiograph? The light intensity (with adjustment) is such that the designated wire in the radiograph is to be made visible.

TUTORIAL
This series will continue... 


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