Section 15 — Inspection

Radiographic Examination

IPE Engineering Practice IPE-EP-15-2-5

Document number: IPE-EP-15-2-5 · Section: 15 — Inspection

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SCOPE

This practice covers the minimum requirements to perform and monitor the Radiographic Inspection Thickness Profile Method by Inflection Point Engineering, LLC Company contractors.

Inspection contractors whose Radiographic Procedures have been submitted and approved by

Inflection Point Engineering, LLC inspection personnel may perform Radiographic Profile Inspections. Any deviation to this practice shall be approved by the procedure described in EP 1–1–3.

An asterisk ( * ) indicates that a decision by the Owner’s Level III or Inspection Authority is required or that additional information is furnished by the Purchaser.

REFERENCES

The latest edition of the following standards and publications are referred to herein.

STANDARDS AND PUBLICATIONS

DEFINITIONS

Owner - Inflection Point Engineering, LLC.

Purchaser - The party placing a direct purchase order. The purchaser is the Owner’s designated representative.

POM (Point of Measurement) - The area marked on the test specimen where the center line of the radiographic beam is directed and where the comparator ball is placed.

Comparator - Device used as a reference standard to correct enlargement of the radiographic image.

“Ricky T” Comparator - Device with a calibrated scale used for direct measurement of wall thickness from radiographs.

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DESCRIPTION OF METHOD

This procedure is for the Radiographic Thickness (Wall Profile) Measurement Inspection Method.

RESPONSIBILITY

The Level III shall be responsible for the content of this procedure and subsequent revisions.

The Inspection Authority shall be responsible to assure that only certified personnel perform these examinations.

CERTIFICATION

Personnel performing examinations to this procedure shall be available on–site certified to the requirements of EP 15–3–2 or an approved contractors written practice.

This procedure or an approved contractors procedure shall be available during these examinations.

The Inflection Point Engineering, LLC Inspection Authority shall assure himself that contract inspectors and Inflection Point Engineering, LLC personnel responsible for obtaining actual thickness measurements from radiographs are qualified.

SAFETY

Radiographic testing shall be performed in accordance with all applicable Inflection Point Engineering, LLC safety requirements, state and federal regulations, and the contractors written procedures.

It is the responsibility for the radiographer to maintain control of the source and the restricted area at all times during radiographic operations.

The radiographer shall exercise every means available, such as collimators, barrier tape, exposure time, visual surveys, and radiation surveys, to ensure that non–radiographic personnel do not receive an exposure to radiation in excess of 2 mr in any one hour at the barrier.

The source shall never be left unattended, except when fully secured in the contractor’s storage container.

EQUIPMENT

Radiographic film viewers shall provide suitable illumination for measurement and viewing of wall profile images.

The equipment and supplies used for radiographic thickness (wall profile) inspection shall be capable of producing quality radiographs in accordance with paragraph 9.0.

The source of radiation shall be Iridium-192 or Cobalt-60. The suggested minimum source strength for IR.-192 is 45 curies. This should be covered in the contract with the Contractor.

8.4 Unless otherwise specified by Inflection Point Engineering, LLC Inspection personnel, all cassettes should be loaded with a single film.

RADIOGRAPHIC QUALITY REQUIREMENTS

• All radiographs shall be free from mechanical, chemical or other blemishes to the extent that they cannot mask or be confused with the image in the area of the radiograph. Such blemishes include, but are not limited to: fogging, water marks or chemical streaks, scratches, finger marks, crimps, dirtiness, static marks, smudges, or tears.
• To check for backscatter radiation, a lead symbol “B” 1/2 inch (13mm) high and 1/16 inch (1.6mm) thick shall be attached to the back of each film cassette. If the “B” image appears on the radiograph, the radiograph may be considered unacceptable.

TECHNIQUE FOR THICKNESS (WALL PROFILE) MEASUREMENT

• The location of each radiograph shall be carefully documented on pipe or equipment drawings. In addition, it is suggested that radiograph locations be marked in the field to prevent any confusion on the part of radiographers.
• Marking methods may include, but are not limited to: stenciling, painting, or tagging.
• Each radiographic film shall be marked, as a minimum, with the following information: plant unit, the date the radiograph was made, drawing number or sketch number if applicable, and the Thickness Measurement Location (TML), if applicable.
• If a comparator ball is used, the ball shall be placed directly at the POM benchmark. It shall be a

1.000 inch diameter stainless steel sphere (1/2” for thinner and smaller diameter pipe) with a tolerance of +/- 0.001 inch. Lead, approximately 1/16 inch thick shall enclose the comparator to prevent over-exposure (burn-off) of the comparator edges. A material, transparent to gamma rays and approximately 1/8 inch thick, shall surround the comparator ball and the lead shall cover the transparent material. The transparent material may be tape, plastic tubing, Plexiglas, etc. The assembled apparatus is called a comparator assembly.

• When making radiographs of non-insulated austenitic stainless steel or other high alloy material (even at ambient temperature), a thin layer of tape or other coating, not to exceed 0.030 inch thick, shall cover the lead on the comparator assembly to prevent it from coming in contact with the pipe metal. At high temperatures, lead may cause cracking of austenitic materials.
• The comparator assembly shall be placed in contact with the pipe OD or insulation cover or jacket. The geometry of the exposure set-up shall be such that the radiographic image of the comparator assembly does not superimpose the radiographic image of the object wall by more than 1/8 inch for non-insulated objects, or 1/8 inch superposition over the insulation of insulated objects.
• For hot objects, where the lead may melt, the comparator assembly shall not come into contact with the object. On hot objects, it is acceptable to use a 1/4 inch thick wall steel tube with the comparator sphere centered in the tube.
• (*) If a “Ricky T” or other measuring device is used, a written procedure supporting its use must be available and approved by the Inflection Point Engineering, LLC Inspection Authority.

• (*) A comparator device is not required. Conventional measurement techniques and tools may be used to obtain the wall thickness of objects examined. All techniques must be approved by the Inflection Point Engineering, LLC Inspection Authority.

RADIATION SOURCE PLACEMENT

• The radiation source shall be placed so the center of the radiation beam strikes the interface between the comparator and the object wall, and is at a right angle to the film (Figure 1). For insulated objects, the radiation source shall be placed so the center of the beam is approximately halfway between the object OD and the outside of the insulation, and is at a right angle to the film (Figure 2).
• The geometry of the exposure set–up shall be such that distortion (ovalness) of the image of the comparator sphere is less than 0.030 inches. The minimum source–to–film distance (SFD) shall be such that the comparator image blow–up does not exceed 15%. The minimum SFD for insulated objects may be calculated by taking half the object diameter plus the insulation thickness and multiplying by six.

Minimum SFD = (half of object OD + insulation) x 6

• Source placement shall be perpendicular to the pipe and film surfaces.
• For exposures where no comparator is used or equal geometry for both walls of the pipe is required, the source shall be centered on the pipe, see Figure 3.
• Source–to–film distance for uninsulated objects, as a minimum, shall be six times the diameter of the pipe. Except when piping diameters of 8 inches and larger are radiographed for one pipe wall, the SFD may be less than 6 pipe diameters.
• The film cassette shall be placed in contact with the pipe or insulation covering.

LEAD STRIP USE

• Approximately 1/16 inch thick x 4 inch wide lead strip shall be placed in between the film cassette and the object to cover the area of interest. The strip shall be long enough to fully cover the diameter of the object and the insulation (six lead screens 0.010” x 4 1/2” x 17” may be used).
• This strip provides shielding that decreases subject contrast and aids in the ability to accurately resolve the object OD.
• The lead strip shall be free of any crimps or other discontinuities which interfere with the interpretation of the radiographic image. This includes the total object image under the lead strip, not just at the wall thickness image.
• When making radiographs of austenitic stainless steel or high alloy objects without insulation (at any temperature), the lead strip shall not come into contact with the metal. A layer of thermal insulation is acceptable to prevent this contact. The lead may be placed in a film cassette.

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USE OF COBALT - 60

The use of Cobalt-60 may be considered as an alternative for Iridium-192 when exposing objects or pipe diameters greater than 6 inches NPS. This can reduce the exposure time required for the larger diameters and enable proper exposure of the large ID cord distance in larger diameter objects or pipe.

(*) Permission and approval of the use of Cobalt-60 must be obtained from the Inflection Point Engineering, LLC Inspection department before it is brought to the job site.

FILM DEVELOPMENT(MANUAL)

Sight development of the film should be used. The film exposure should be such that the film development time falls between 5 and 8 minutes @ 68 degrees for manual development. If, during sight developing, a development time outside of the 5 to 8 minute range is necessary, that is acceptable; however, it is an indication that the exposure time for future shots needs to be adjusted accordingly.

If automatic film processors are used, they shall produce quality film as required by 9.1.

REVIEW OF RADIOGRAPHS

All profile radiographs shall be reviewed by the radiographer before submitting them to the Inflection Point Engineering, LLC Inspection department. If film quality or geometric requirements are not met, the radiograph shall be re-shot at no cost to Inflection Point Engineering, LLC.

All profile radiographs shall be reviewed by the radiographer before submitting them to the Inflection Point Engineering, LLC Inspection department. If film quality or geometric requirements are not met, the radiograph shall be reshot at no cost to Inflection Point Engineering, LLC.

If conditions exist which cause the technician to be unable to meet the requirements, he should notify the Inflection Point Engineering, LLC Inspection personnel of those conditions before the radiographic exposure.

If a condition is noted which is judged to affect the pressure retaining integrity of the pipe, the radiographer shall notify the Inflection Point Engineering, LLC Inspection personnel within the work day.

MEASURING THICKNESS AT THE RECORDING POINT (POM)

(*) The radiographer shall measure the thickness of the POM on each radiograph, unless instructed otherwise by Inflection Point Engineering, LLC Inspection personnel.

Thickness measurements of the POM shall be taken directly under the comparator within the area covered by the width of the comparator. A scribe or other instrument shall be used to make a scratch, mark or a hole on the radiograph indicating exactly where the wall thickness and comparator diameter was measured.

• The wall and comparator measurements shall be made to 2 decimal places. Dial or digital calipers shall be used to make the measurements or the IPE Pipe Wall Profile Scale.
• The actual wall thickness will be determined by:

Actual Wall Thickness = Actual Comparator (Ball) Diameter X Measured Wall

Measured Comparator Diameter

• The actual POM thickness shall be indicated on the film using a grease pencil or similar marker.
• If a “Ricky T” or other measuring device is used, measurements shall be made in accordance with approved written procedures.
• If no comparator or other measuring device is used, conventional measurements and calculations may be used to establish the actual wall thickness. In this case, the following calculations is used.

Actual Wall Thickness = Actual Pipe Diameter x Measured Wall Thickness

Measured Pipe Diameter

• Also, the IPE Wall Profile Scales may be used to obtain the actual wall thickness. These scales have instructions for their use printed on them.
• If the IPE Wall Profile Scales are used, the maximum enlargement (blow–up) shall be 15%. (The correction factor, Actual Pipe Diameter , shall be 0.85 or greater; ideal = 1.0.)

Measured Pipe Diameter

• For all wall profile radiographs, the THINNEST actual wall thickness noted on all components covered by the radiograph shall be recorded for corrosion rate calculations.

QUALITY OF THE WALL PROFILE IMAGE

• In addition to the quality requirements of Section 9 and 10, the radiographer is responsible for maintaining the quality of the profile image:
• Blow-up shall not exceed 15%.
• Geometric distortion (comparator ovalness) shall not exceed 0.030 inch.
• Super imposition of the comparator assembly shall not exceed 1/8 inch.
• Underexposure - the ID of the pipe must be visible.
• Overexposure - the lead strip shall be visible.
• The POM, the comparator, and all film identification shall be visible.
• Excessive unsharpness or blurring of the image is not permitted.

EVALUATION OF RADIOGRAPHS

• Prior to being presented to Inflection Point Engineering, LLC Inspection, radiographs shall be examined for quality in accordance with Sections 9, 10 and 17 of this procedure.
• If Inflection Point Engineering, LLC Inspection has provided the NDE contractor with acceptance criteria, the radiographer or the technician responsible for measuring the wall thickness shall either accept or reject the POM based on that criteria.
• If no acceptance criteria are furnished, the radiographer shall simply report the thickness measurement calculated at each POM.

• The result of thickness measurements shall be recorded in Table 1 or other approved form as well as on the radiographs.
• Unless otherwise directed by Inflection Point Engineering, LLC Inspection, radiographs shall be submitted in envelopes divided individually with the interleaf’s from the original film boxes.

REPORTS OF RADIOGRAPHIC ACTIVITIES & SAFETY

• The radiographer shall provide all reports and time sheets required by the responsible Inflection Point Engineering, LLC Inspection Authority on a daily basis.
• The radiographer should complete a technique sheet for wall profile radiographs of various size pipes and configurations. This sheet shall include the variables needed to repeat a quality radiograph at the same or similar location. (Table 1)
• The radiographer is responsible for completing daily all required reports, including Table 1 or equivalent and a Field Radiation Survey.

20.0 TABLES

TABLE 1

WALL PROFILE RADIOGRAPHY REPORT

21.0 FIGURES

FIGURE 1

STANDARD TECHNIQUE FOR RADIOGRAPHIC THICKNESS MEASUREMENT USING RADIOGRAPHYS

FIGURE 2

STANDARD TECHNIQUE FOR RADIOGRAPHIC THICKNESS MEASUREMENT USING RADIOGRAPHY ON INSULATED PIPING SYSTEMS

FIGURE 3

WALL PROFILES WITHOUT CAMPARATORS

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