We all know that stainless steel pipes need to be pickled and passivated before leaving the factory. However, sometimes users ask for re-degreasing of the pipes? For pipes, the more reasonable degreasing should be completed on-site, that is, after all the pipes are installed, the degreasing should be carried out in the entire pipe system.
With the increasing level of industrialization in my country and the vigorous development of projects in industries such as petrochemicals, natural gas, medical equipment, instrumentation, aviation, and aerospace, the requirements for stainless steel pipe technology are getting higher and higher. For example, for the cleanliness of the pipe, some users require that there should be no free rust, large particles of dust, welding slag, grease and other impurities inside.
Among them, the cleanliness requirements of oxygen pipelines are quite demanding. Most of the oxygen pipelines transport oxygen with a purity greater than 99.99%, with high pressure and fast flow rate. If the internal cleanliness of the pipe cannot be guaranteed, trace amounts of oil and metal ions in the pipeline may oxidize and collide with high-pressure pure oxygen, generating electric sparks and causing unimaginable serious consequences, or even tragic accidents.
Therefore, according to the process requirements, the newly built equipment pipeline needs to use chemical cleaning methods to remove the oil and other impurities on the internal pipe wall before the device is started. At the same time, the supplier will be required to decrease the pipeline.
Degreasing and cleaning steps for stainless steel oxygen pipelines: water flushing → manual wiping and degreasing → water flushing → compressed air (or nitrogen) purging.
Water flushing Use a small high-pressure water cleaning equipment to flush during flushing, and the pressure is controlled at about 0.6Mpa to ensure that the impurities inside the pipeline are flushed clean. The purpose is to remove dust, sediment, detached metal oxides and other loose dirt in the pipeline.
Manual wiping and degreasing Inject the cleaning and degreasing mixture into the cleaning basin, add it according to the proportion, mix it evenly, and use it repeatedly. During the cleaning process, the cleanliness of the degreasing cleaning liquid should be monitored. If the color of the degreasing cleaning liquid becomes turbid, the existing degreasing liquid needs to be drained and the degreasing cleaning liquid needs to be reconfigured. The purpose is to remove various types of engine oil, graphite, anti-rust oil, and other organic matter in the pipeline to ensure that the pipeline is clean inside during installation and meets the requirements of equipment operation.
Water flushing After the pipeline is degreased, flush it with a large amount of water. When the flushing water flowing out of the pipeline is clean, the water flushing can be ended. The purpose of water flushing after degreasing is to flush away the degreasing residue in the pipeline.
Compressed air (or nitrogen) purging Use oil-free compressed air (or nitrogen) to purge, and after the inside of the pipeline is dried, use a clean plastic cloth to wrap and seal the pipeline or parts, so as to ensure the cleanliness of the inside of the pipeline and avoid secondary pollution.
Acceptance method for degreasing of stainless steel pipes Pipeline degreasing treatment should use the degreasing solvent and degreasing requirements specified in the design. If not specified in the design, carbon tetrachloride can be used for degreasing to check whether the degreasing is qualified.
After the pipeline is degreased and cleaned, the following requirements should be met:
1) Use ultraviolet light with a wavelength of 320-380nm to check the inner wall of the pipeline. There should be no grease fluorescence.
2) Wipe the inner wall of the pipeline with clean and dry white filter paper. There should be no traces of oil on the paper.
3) use a degreasing solvent to detect that the grease content does not exceed the requirements of the client.
4) Other relevant technical indicators proposed by the client.
The chemical cleaning and degreasing process of stainless steel oxygen pipelines standardize the construction process of oxygen pipeline cleaning and degreasing, greatly improves the internal cleanliness of oxygen pipelines, and is a reliable guarantee for the safe and efficient operation of oxygen pipelines. It is worthy of attention and promotion by stainless steel pipe manufacturers.
Post time: Apr-07-2025