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August 21 - August 25, 2017

How clean must the compressed-air supply be for blast cleaning, blow down and painting? How is cleanliness of the air determined?

Selected Answers

From Rahil Shaikh of Link Middle East LLC on September 7, 2017:
Compressed air blast check can determine presence of any contamination by using Blotter paper test per ASTM 4285. Take a blotter paper and stick it on a clipboard. Let the air compressor run on 90 PSI for 5 minutes without any abrasive. After 5 minutes reduce the speed to 50 PSI and hold it against the blotter paper for 1 minute at a range of 45-60 cm  from the test board.After one minute, check the blotter paper for any oil or water traces.

Compressed air must be free of oil, water and contaminants. This is required not only for blasting or blow down prior to painting,  but also for air supplied into breathing equipment for blaster safety. Dry air (moisture-free) must also be used for painting application to keep the spray machine in good condition. If not, moisture can damage internal parts of sprayer and machine efficiency will be affected. Cleanliness of the air can be determined by using blotter paper or any absorbent-type white cloth. Refer to standard ASTM D4285.

From wan mohamad nor wan rahmanVV of ANTAP SEMENANJUNG SDN. BHD. on August 22, 2017:
The cleanliness of the air will be determined using the blotter paper test.

From ROBERTO CANTERA of CPPQ on August 20, 2017:
The air supplying the compressor must be free of impurities such as water, oil or other contaminants affecting the surface and the coating. For these cases the ASTM D4285 is used with the blotter paper test.

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Tagged categories: Abrasive blasting; Blasting; Surface preparation; Surface Preparation; Surface preparation equipment

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