Why some stainless steel pipes need to be degreased

We all know that when stainless steel pipes leave the factory, they need to be pickled and passivated. However, sometimes users encounter re-degreasing treatment for pipelines? As far as the pipeline is concerned, the more reasonable degreasing should be completed on-site, that is, after the pipeline is completely installed, the degreasing treatment should be carried out in the entire pipeline system. Generally, manufacturers will not be allowed to perform degreasing treatment. So, what exactly is required for manufacturers to degrease pipes?
With the increasing level of industrialization in my country and the vigorous development of petrochemical, natural gas, medical equipment, instrumentation, aviation, aerospace, and other industrial projects, the requirements for stainless steel pipe technology are becoming higher and higher. For example, the cleanliness in the pipeline requires users to have free rust, large particles of dust, welding slag, grease, and other impurities.
Among them, the cleanliness requirements of the oxygen pipeline are quite demanding. Most of the oxygen pipelines transport oxygen with a purity greater than 99.99%, which has high pressure and a fast flow rate. If the inside of the pipeline is not guaranteed to be clean, trace oil and metal ions in the pipeline may oxidize and collide with high-pressure pure oxygen, resulting in electric sparks. The unthinkable serious consequences have even led to heavy accidents.
Therefore, the newly-built equipment pipeline needs to be chemically cleaned to remove the oil stains and other impurities on the internal pipe wall before the device is started according to the process requirements. At the same time, the supplier will also be required to degrease the pipeline.
Stainless steel oxygen pipeline degreasing and cleaning steps: water rinse → manual wipe degreasing → water rinse → compressed air (or nitrogen) purge.

Water washing When washing, use small high-pressure water washing equipment to wash, the pressure is controlled at about 0.6Mpa, to ensure that impurities inside the pipe are washed clean. The purpose is to remove ash, sediment, detached metal oxides, and other loose dirt in the pipeline.
Manually wipe off the degreasing Inject the cleaning and degreasing mixture into the cleaning basin, add it in proportion, mix it evenly and use it, and wipe 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 dirty, the existing degreasing liquid should be drained and the degreasing cleaning liquid should be reconfigured. The purpose is to remove all kinds of organic materials such as engine oil, graphite, anti-rust oil, etc. in the pipeline, so as to ensure the internal cleanliness of the pipeline during installation and meet the requirements of equipment operation.
Water rinsing After degreasing the pipeline, rinse with a large amount of water. When the rinsing water flowing out of the pipeline is clean, the water rinse can be ended. The purpose of water washing after degreasing is to wash away the degreasing residue in the pipeline.
Compressed air (or nitrogen) purge Use oil-free compressed air (or nitrogen) to purge and dry the inside of the pipeline with a clean plastic cloth to wrap and seal the pipeline or parts, so as to ensure the cleanliness of the pipeline, avoid two Secondary pollutions.
Acceptance method for degreasing of stainless steel pipes Degreasing solvents and requirements for degreasing specified in the design of pipeline degreasing treatment are required. If the design does not specify, carbon tetrachloride can be used for degreasing to check whether the degreasing is qualified.

Post time: 2020-07-14