Blasting purge

After the installation of the pipes in the system is complete, air purging is necessary to remove all debris such as welding slag, flux residues, foreign particles, and dust from within the pipes. This requires a certain flow rate of air inside the pipes; however, construction sites usually do not have air compressors capable of generating such high flow rates, and using high-flow air for purging also results in significant waste. Therefore, the ends of the pipes to be purged can be sealed using asbestos rubber gaskets or thin metal sheets (depending on the size of the pipes). By using an air compressor to increase the pressure in the system to the breaking point of the membrane (0.6–0.7 MPa), the compressed air inside the system escapes at high speed through the rupture point, thereby achieving the required flow rate. This allows all debris such as welding slag, flux residues, foreign particles, and dust to be expelled along with the airflow, thus achieving the goal of clearing these contaminants from the pipes. This process is known as burst purging. By using explosive purging, pipes with large diameters ranging from 100 to 600 mm can be purged. For cleaning units that lack large compressors, this method helps to overcome the challenges associated with purging such large-diameter pipes. Explosive purging also takes advantage of the vibrations generated by explosions to improve the efficiency in removing dirt from within the pipes; it is therefore an advanced technique. For pipes such as hydraulic pipelines where high cleanliness is required, this method can reduce the time needed for system cleaning, which is beneficial for shortening the commissioning time and enabling operations to start as soon as possible. General guidelines state that: 1) The pressure used for explosive purging shall not exceed the design pressure of the pipe, nor shall it be higher than 0.3 MPa. (Based on our construction experience, if rubber sheets are used as blind plates, they generally rupture when the pressure reaches around 0.3 MPa.) 2: The length of the pipeline to be purged each time should not exceed 500 m ； When the pipeline length exceeds 500 m, it is advisable to purge it in sections. 3: When it appears, visually, that there is no smoke or dust in the exhaust gas, a white cloth or a wooden target painted white should be placed at the exhaust outlet for testing; if no rust, dust, or other contaminants are present on the target within 5 minutes, it is considered acceptable.

When using asbestos board, should a light cross be marked on its surface?

Does it mean that the same pipeline needs to be blown up multiple times in a row? Until it is completely purged?

Thank you! I want to ask this question too. I also would like to ask the original poster: how are the material and thickness of the burst disk determined? Thank you!

I have to purge the acetylene pipes every 2 months, using a large amount of nitrogen each time. I would like to ask whether this explosive purging method is effective for acetylene pipes with a diameter of less than 100 MM

For blasting purging, it is necessary to select a blind plate based on the diameter of the pipeline; the larger the diameter of the pipeline, the greater the area of the blind plate, and the higher the pressure exerted on it, making it more likely for the blind plate to burst. In such cases, a thicker blind plate can be used. If the blind plate is less likely to burst, a cross-shaped cut can be made on its surface； The standard for cleanliness is to first ensure that no dust is visible to the eye before shooting; a target free of debris is considered qualified.