Source Size refers to radioactive material sources and Focal spot refers to X-Ray machines.
It is interesting to note that for X-Ray machine of >1000KV and sources other than Iridium the code is not specifying the method of determining the source size.
Remember: pinhole imaging is related to X-Ray source size determination.
- National Standard step tablet
- Step wedge calibration film
- Densitometer
- Step wedge comparison film
Prior to first use, if the step wedge calibration film is maintained in the original light-tight and waterproof sealed package as supplied by the manufacturer, it can used directly.
Step wedge calibration films may be used without verification for one year upon opening provided it is within the manufacturers stated shelf life.
The step wedge calibration film shall have been verified within the last year by comparison with a national standard step tablet.
3. Step Wedge Comparison Film:
Step wedge comparison film is used for day-to-day density checking purpose.
- Shall be verified prior to first use
- Shall be verified by a calibrated densitometer
- The step wedge comparison film is acceptable if the density readings do not vary by more than 士0.1 density units from the density stated on the step wedge comparison film
Periodic Verification
This refers to the verification's that are to be done on densitometer and step wedge comparison film on day-to-day basis.
Periodic Verification of Densitometer
Periodic calibration verification checks shall be performed on any of the conditions which comes first.
- The begining of each shift
- After 8hrs of continuous use
- After change of apertures
- Densitometer calibrations shall be documented
- Periodic densitometer verification checks do not have to be documented
- Step wedge calibration film verification shall be documented
- Step wedge comparison film verification shall be documented.
Whenever practical - Single Wall exposure technique; if not practical double-wall technique to be used.
No of
exposures required: Exposures should
provide proper coverage.
Single-wall technique:
The radiation passes through one wall of weld/material
Double-Wall technique:
1. Single-Wall viewing
Weld/Material on the film side is viewed for acceptance. When complete coverage is required for circumferential welds (materials), a minimum of three exposures taken 120 deg to each other shall be made.
2. Double-Wall viewing
Materials and for welds in components 3 1/2 in. (89 mm) or less in nominal outside diameter can be radiographed by this technique.
a. Ellipse
For welds, the radiation beam may be offset from the plane of the weld at an angle sufficient to separate the images of the source-side and film-side portions of the weld so that there is no overlap of the areas to be interpreted. When complete coverage is required, a minimum of two exposures taken 90 deg to each other shall be made for each joint.
b. Superimpose
As an alternative, the weld may be
radiographed with the radiation beam positioned so that the images of both
walls are superimposed. When complete coverage is required, a minimum of
three exposures taken at either 60 deg or 120 deg to each other shall be
made for each joint.
T-272 Radiation Energy
Radiation energy is selected so that it
shall achieve the density and IQI image requirements of Article 2 of ASME BPVC
Sec V.
Note: The density and IQI requirements of Article 2
should be met in a radiograph and NOT of construction code.
T-273 Direction of Radiation
The direction of the central beam of
radiation should be centered on the area of interest whenever practical.
This blog is not a replacement for the training provided by authorized partners/experienced institutions nor this blog guarantee success in API exams. This blog is the outcome of the approach followed by the author for the preparation of API exams.
Disclaimer: Photos are taken from different websites. If this violates any copyright rules this will be removed. Please inform me if any of the photos or contents violate copyright rules. (through 13hareesh13@gmail.com). This blog is meant for educational purposes only. If it is used for any other means without the written consent from the author, the author will not be responsible. The author does not guarantee the accuracy of the data used in this blog. All the information, data, photo/image, calculations presented in this blog should be used at the sole risk of the user. The blogger is not liable or responsible in any way for any damage, losses or costs arising from the use of the blog for any purpose whatsoever or whosoever it may be. The blog is to be used at your sole risk and responsibility.
Comments
Post a Comment