ASTM D7091 PDF
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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Measuring Dry Film Coating Thickness According to SSPC-PA 2
A minimum of three gage readings is obtained in each spot, culminating in a minimum of 15 gage readings within an area. Additionally, most manufacturers of high performance coatings will warranty coating systems based upon, in part, achieving the proper thickness of each layer and the total coating system.
We can gather hundreds of gage readings in a relatively short time; batch the measurements; print the data or upload it to a computer for graphing; report the highest, the lowest, the mean, and standard deviation of the collected data; incorporate digital images astj the structure or coated area; and even program the gage to produce an audible signal if a spot measurement is outside of the tolerance range.
The most current version of the ASTM standard focuses on proper gage use, while SSPC-PA 2 focuses primarily on the frequency of measurements and the acceptability of the acquired measurements. Gage Calibration, Accuracy Verification and Adjustment. Unusually high or low gage readings that cannot be repeated consistently are discarded.
It is the responsibility of the user of this standard to establish appropriate safety and health practices d70991 determine the applicability of regulatory limitations prior to use. It is important to note that both documents address the measurement of the DFT of coatings on ferrous and non-ferrous metal substrates. Otherwise the reliability of the gage is suspect.
One conduit is through training and education.
Measuring Coating Thickness According To SSPC-PA2 – Update KTA University
Accuracy statements frequently include a? We have allowed technology to make it more complex, yet easier. This practice does not address the use of ultrasonic coating thickness gages. There are three categories of coated area: The scale is nonlinear. These gages use electronic circuitry to convert a reference signal into coating thickness and are more popular than Type 1 gages.
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.
Pipe spools that are not loaded onto a rack or cart are typically measured individually Fig. The total number of spot and area measurements is based on the total square footage of pipe on the cart or rack.
Verification of gage accuracy is typically performed using certified coated thickness standards for Type 1 or Type 2 gages or certified shims Type 2 gages. Use of the gage outside of this range may generate false coating thickness measurements and may damage the instrument. Change is never easy…. SSPC-PA 2 states that a minimum of 10 locations arbitrarily spaced should be measured one reading per locationthen averaged.
Test Method D should be referenced for this application.
For areas of coating to 1, square feet, three random areas are selected and measured. Because the coating may not perform at the lower thickness, it is important for the specifier ast, indicate an acceptable range for each coating layer.
The author, Bill Corbett, has replied via email. Conformance to Specified Thickness: The user of this equipment must be knowledgeable in the proper operation of these devices, including methods for verifying the accuracy of the equipment prior to, during and after use as well as measurement procedures. The above article was very informative and useful, thanks for sharing it. SSPC-PA 2 aetm that a minimum of 10 arbitrarily spaced locations should be measured one reading per location and then averaged.
January 28, at 5: For the purpose of final acceptance of the total dry film thickness, the cumulative thickness of all coating layers in each area must be no less than the cumulative minimum specified thickness and no greater than the cumulative maximum specified thickness. Determining the Magnitude of Non-conforming Thickness. All of the area within five feet of any non-compliant spot measurement is considered non-compliant. A one-year calibration interval is a typical starting point suggested by gage manufacturers.
October 16, at 2: February 7, at 2: The manufacturers provide information for the adjustment and use of these gages, normally in the d091 of operating instructions. All definitions related to gage calibration, accuracy and adjustment are incorporated by reference in ASTM D On complex structures or in other cases where making spot measurements at five-foot intervals is not practical, spot measurements are taken on repeating structural units or elements of structural units.
The number of areas that must be measured for coating thickness varies, depending on the size of the coated area. SSPC-PA 2 contains three definitions that are critical to understanding this next area of discussion.