Test Air Quality as Per ASTM D 4285: Air Compressor Blotter Test

What is ASTM D 4285? Air Compressor Blotter Test Based on ASTM D 4285

Air quality is one of the critical parameters in abrasive blast cleaning, especially for the satisfactory success of applications involving coats. Among the several methods used for detecting traces of contamination in compressed air is known as the Blotter Test or Test Air Quality as Per ASTM D 4285. Such contamination can be in the form of oil, water, or any other type of foreign matter that could degrade the performance of the coating. Therefore, it is essential to conduct this test before beginning work shifts and abrasive blasting.

Why is the Blotter Test important?

Compressed air is a significant ingredient of abrasive blast cleaning. Contaminates, like oil or water in such compressed air, could adversely impact the performance of an applied coating. The coating system could be exposed to adhesion failure, blistering, or corrosion by such contaminants.

You ensure that the compressed air supply has minimum harmful contamination to maintain integrity for the coating process by conducting the Test Air Quality as Per ASTM D 4285. The test method is simple and depends on visual examination in order to detect impurities in the air.

Test Intervals

This test is done at intervals required by the specifications of the project. It is usually performed at the beginning of every working shift, or when the air supply system is switched.

Equipment Required for the Blotter Test

Following equipment are required to carry out the Test Air Quality as Per ASTM D 4285:

Blotter Paper Pack: White absorbent papers, usually sized 8″ x 8″ or any other convenient size.
Rigid Backing : A hard surface to mount the blotter paper.
Duct Tape: To tape the blotter paper onto the backing.
Compressed Air System: Including filters, driers and separators.

Air Quality Step-by-Step Testing Procedure

Step 1. Preparation

Fix blotter paper onto the rigid support, holding the entire assembly together by way of duct tape.
Filters and driers of all kinds throughout the air supply should be set on the open/clean positions with the blow-line out until the existence of contamination may no longer be visually perceived in it.

Step 2. Attain Operating Conditions

Let the compressed air system reach the normal operating conditions. It will then ensure that the test represents real working conditions.

Get Rid of Accumulated Condensation

Release the compressed air to get rid of accumulated condensation in the system. The process will help eliminate possible sources of contamination.

Carry Out the Test

Place the blotter paper as near to the point of use of the compressed air system as feasible, but always downstream of in-line oil and water separators.
Allow the air to blow directly onto the blotter paper for at least one minute. That is enough time to allow any contaminant trace to be detected.

Examination of the Blotter Paper

After the test, visually inspect the blotter paper for oil, water, or discoloration. Oil contamination usually has a smell.
If the paper is free of any discoloration, oil, or water marks, it indicates good air quality. If contaminants are visible, the test is rejected and the air supply system needs to be cleaned before a new test.

Optional Ultraviolet Light Method

In a dark room, let your eyes adjust for about five minutes.
Shine ultraviolet light on the blotter paper. If the paper is shiny or glossy, then it is oil contaminated. Water contamination will not show this glossiness.

Record Results

Mark and record the blotter papers used in the test for quality control records. These records will be considered evidence of compliance with ASTM D 4285, and that air quality is appropriate.

Key Benefits of Testing Air Quality

Conducting the Test Air Quality in accordance with ASTM D 4285 has the following benefits:

Prevents coating failures due to contamination.
Meets project specifications and industry standards.
It improves the quality and durability of the coating system in general.
It instills confidence in the blasting and coating processes.

Conclusion

Test Air Quality as Per ASTM D 4285 is one of the essential processes to ensure that abrasive blast cleaning and coating operations are successful. With this straightforward yet effective test, you will be able to identify and remove contaminants from compressed air so that your coating process will not be affected. Remember to always document the result for quality assurance and project compliance. This simple visual examination can make quite a difference regarding the achievement of long-lasting reliable coatings.