This standard is issued under the fixed designation D ; the number 1 This practice is under the jurisdiction of ASTM Committee D01 on Paint and. Related. In nearly the same timeframe, the version of ASTM D, “Standard Practice for Nondestructive Measurement of Dry Film Thickness of. ASTM D describes three operational steps that must be performed prior to coating thickness measurement to help assure the reliability of.
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Also, uncoated shims of flat plastic sheet with assigned ast traceable to a national metrology institution. Appendix 9 added in Qstm step sounds reasonably straightforward but poses several hidden challenges.
This includes personalizing content and advertising. A Base Metal Reading Astmm is obtained and subtracted from the coating thickness to compensate for the effect of roughnessas described in 7. Frequency for Measurement of Coating Thickness 8. Secondly, some Type 2 gages cannot be adjusted. More recently within zstm past year or soTestex developed a new replica tape, which when inserted into the DeFelsko PosiTector Replica Tape Reader RTR-P produces 3-D color image of peak density and displays peak height as well as peak density Pd, peaks per inch2.
Satm is no standard time interval for re-calibration, nor is one absolutely required, but a calibration interval can be established based on experience and the work environment.
October 27, at 5: The type of reference standard used to verify gage accuracy should be predicated upon the type that provides the best and most appropriate method of veri? For areas of coating exceeding 1, square feet, three random areas are selected from the first 1, square feet, along with one additional area for each additional 1, square feet.
If the gage is dropped or suspected of giving erroneous readings during the work shift, its accuracy should be rechecked. December 28, at 6: Change is never easy…. Asm, several Type 2 electronic gage manufacturers offer a variety of probe configurations, some of which are less affected by proximity to edges and are designed to better measure the thickness of coatings on edges Figure The thickness of the coating is displayed digitally.
I am assuming you are using an electronic gage: If shims are selected to verify gage accuracy, they should be placed on a smooth steel plate zero-plate.
Appendix 7 was added to accommodate pipe coaters that need to determine coating thickness conformance on non-flat or non-plate areas, including smaller pipe sections on a cart or rack and longer pipe spools. Figure 13 courtesy of SSPC. Equipment manufacturers produce nondestructive coating thickness testing gages that are used to measure the cumulative or individual thickness of the coating layers, after they are dry.
In general, access to tight areas is easier with Type 2 gages, especially those equipped with separate or remote probes. Two of the eight appendices were added in the remaining were in the edition and are highlighted below. On complex structures or in other cases where making spot measurements at 5-foot intervals is not practical, spot measurements are taken on repeating structural units or elements of structural units.
Special attention will be given in the article to how PA 2 addresses the required number of coating thickness measurements; the acceptability of gage readings, spot measurements, and area measurements; nonconforming thickness; measuring DFT on coated edges; and measuring DFT on pipe exteriors. Verifying accuracy of Type 2 gage on a certified coated standard Fig. For a given measurement direction or unit measurement, any compliant area or unit preceding a non-compliant area or unit is designated as suspect, and as such is subject to re-inspection after corrective measures are performed.
Yet the requirements of SSPC-PA 2 regarding gage calibration, verification of gage accuracy and adjustment procedures, the number of measurements to obtain, and the tolerance of the measurements are complex and should be fully understood by the specification writer before invoking PA 2 in a contract.
References to the frequency of measurements were removed from the ASTM standard. Historical Version s – view previous versions of standard. October 16, at 2: ASTM D describes three operational steps that must be performed prior to coating thickness measurement to help assure the reliability of the measurements.
I am assuming you are using an electronic gage:. Any unusually high or low gage readings that are not repeated consistently are discarded. The magnitude of nonconforming thickness assessed by obtaining spot measurements in eight equally spaced directions radiating outward from the nonconforming area. Arguably the most critical section in the document, Section 8 describes how many areas to check, the size of the areas, the number of measurements to obtain in each area and what steps to take if spot or area measurements do not conform to the specification.
This method is used when the largest dimension of the unit is less than 10 feet. The arithmetic mean of these values becomes the Base Metal Reading.
Users of this standard are expressly advised that determination of the awtm of any such patent rights, and the risk of infringement of such rights, are entirely their own responsibility. The average of the three d7901 gage readings is the spot measurement; the average of five spot measurements is the area measurement. The gage should be veri? Even if a project speci?
The accuracy of Type 1 magnetic pull-off gages is verified by placing the gage probe onto a certified coated thickness standard Figs. The number of peaks and valleys is also important.
One of the issues that needs to be explained and discussed is using Test-Tex paper for measuring profile. If no Restriction Level is specified, default is based on conformance requirement.
The average of the three acceptable gage readings is the spot measurement.
For areas containing less than square feet of d091 surface, every square foot area must be measured for coating thickness. Accordingly, these gages cannot distinguish the thickness of individual layers after they have all been applied.
Method for Measuring the Dry Film Thickness of Coatings on Edges For decades, the industry was cautioned about taking coating thickness measurements within one inch of an edge, let alone on an edge. These gages use electronic circuitry to convert a reference signal into coating thickness and are more popular that Type 1 gages. For areas of coating to 1, square feet, three random areas are selected and measured.
Type 1 gages should not be used on soft or tacky coatings, as the magnet may adhere to the coating causing false low measurements, or coating materials may dry on the magnet causing false high measurements. It describes the methods and recommended frequency for verifying the accuracy of gages and for adjusting optimizing the equipment, describes a frequency for measuring the thickness of the coating s and lists the reporting recommendations.