As we all know, stainless steel pipes leaving the factory often require pickling and passivation treatments. However, users sometimes request a re-degreasing process. For pipelines, it’s generally more practical to perform this degreasing on-site, meaning after the pipeline has been safely installed, the entire system undergoes a thorough degreasing process. Manufacturers typically aren’t involved in degreasing the pipes themselves.
With the rapid advancement of industrialization in our country and the flourishing growth of projects in sectors like petrochemicals, natural gas, pharmaceutical equipment, instrumentation, aviation, and aerospace, the demands placed on stainless steel pipe processing have been increasing month by month. For instance, there's an emphasis on maintaining the cleanliness of pipelines to prevent issues like free rust, large dust particles, welding slag, grease, and other contaminants.
Among these, the cleanliness standards for oxygen pipelines are particularly stringent. Many oxygen pipelines transport oxygen with a purity exceeding 99.99%, under high pressure and at fast flow rates. If the internal cleanliness of these pipelines isn't guaranteed, trace amounts of oil and metal ions could oxidize when exposed to high-pressure pure oxygen, potentially sparking electric discharges and leading to catastrophic accidents. This has indeed happened in some cases.
Therefore, new equipment pipelines must be chemically cleaned before being put into operation according to the process requirements. Users also expect suppliers to degrease the pipelines accordingly.
The steps for degreasing and cleaning stainless steel oxygen pipelines include: water rinsing - manual degreasing - water rinsing - compressed air (or nitrogen) purge.
When using water for rinsing, small high-pressure water jets should be used to clean the pipes thoroughly. The pressure should be kept around 0.6 Mpa to ensure any impurities inside are removed. The goal here is to get rid of accumulated ash, mud, loose metal oxides, and other debris.
Manual degreasing involves injecting the cleaning solvent into a basin, mixing it in proportion, and applying it repeatedly. Throughout the process, the cleanliness of the degreasing solution should be monitored. If the solution becomes dirty, it should be replaced. The aim is to eliminate various types of oils, graphite, rust inhibitors, and other organic materials from the pipeline, ensuring the internal cleanliness of the pipe during installation and meeting the operational requirements of the equipment.
After degreasing, the pipe should be thoroughly rinsed with water. Once the rinse water coming out of the pipe appears clean, the water rinse process is complete. The purpose of this step is to wash away any remaining degreaser residue inside the pipe.
Finally, the pipeline is purged with oil-free, contaminant-free compressed air (or nitrogen). The pipe should then be dried with a clean plastic cloth to seal it off, ensuring its cleanliness and preventing secondary contamination.
For stainless steel pipe degreasing acceptance, the method used should follow the specifications and requirements outlined in the design. If no specific design is provided, carbon tetrafluoride can be used for degreasing, and the results can be checked to confirm if the degreasing was successful.
This information is provided by Wenzhou Moranti Steel Industry Co., Ltd. Please make sure to credit the source if you choose to reprint this content.
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