![]() We will be updating and growing this site with more and more of industrial inspection related articles. Dry Film Thickness Instrument Calibration Some paint manufacturers do not advise the sanding and instruct re-blasting and repeating the coating process. What should be done if it was higher than 12? That depends on the coating specification if permitted by coating specification, then should be subjected to the sanding (by sand paper) to reduce paint DFT, if not indicated in the coating specification, then the painting manufacturer should be consulted. What should be done if it was less than 9 mil? Another coat should be applied to reach the required DFT value, and measurement should be repeated. The spots are Ok, now let calculate the average of these 5 spots which will represent this 100 square ft.Īve of 10.5, 12.6, 7.6, 7.3, and 14.3 is 10.46, and this value falls within 9 to 12 mil, so the DFT in this 100 square ft is OK, it would have been rejected if it was less than 9 or higher than 12 mil. Let's continue with above example, you proceed with dry film thickness readings, and you get following values: However, your 5 spots average should be within specified range. Second, you have wider acceptance range for spot reading it mean 80% to 120%. So actually you have two concessions here, first single gage reading does not matter, even unusual very low gage reading can be eliminated from averaging. After completion, you should average these 5 spots, and the average should be within the acceptance criteria it means 9 thru 12 mils. You need to take 5 spots and each with 3 gage readings so that the total readings will be 15 gage readings. So the average of 3 readings (within a circle of 1.5 inch) should be within 7.2 thru 14.4. ![]() In above example, the 80% of 9 mil will be 7.2 mil and 120 % of 12 will be 14.4 mil. Spot reading shall be within 80% to 120% of specified values. The standard also goes higher than this and says, the unusual very low amount can be ignored from recording and calculation. In above example, you can have a gage reading for 3 mil or 5 mil and with these gage reading the paint is not going to be rejected. Start with considering an area about 100 square ft and then select a spot, assume a circle with a diameter of 1.5 inch and take 3 gage readings.Īs per SSPC-PA 2, a single reading does not matter and is not considered as acceptance criteria. This happens because of the surface irregularities. Spot Measurement: It is the average of 3 gage reading within a circle of 1.5 inchĪrea Measurement: The average of 5 spots in each 100 square ft.Įxpect to get different gage reading even if they are even too close to each other. ![]() Gage Reading: It is the single reading, the point you place the instrument probe. The SSPC-PA 2 outlines a test procedure based on following definitions: ![]()
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