Chemical Treatment and Passivation of Pipes

Steel “Passivation” refers to the process of chemical removal of iron contaminates left of the surface of stainless steel and other steel parts after machining.  Passivation maximizes resistance to corrosion.  A number of different passivation methods exists for various types of steel.
Assembled, welded and closed circuits, such as pipes, in order to be cleaned, must be flushed by circulating liquid through the pipes.  The cleaning process is both chemical and physical.  The minimum flow rate of the solution through the pipes should be at least one (1) meter per second.  Pipeline flow rate and capacity must be considered as well as the diameter of the pipe. Pipes should be tested for water tightness after installation and connection to the hoses that complete the system.  Special pickling materials should be used to ensure the integrity of the system. Complete removal of rust is only possible by chemical methods.  Not all of these methods provide for a complete solution and removal of all rusts deposits.  This may be further achieved by the forced, high pressure circulation of special acidic and alkaline solutions that control chemical reactions. The solution should move through the pipes until the chemical reactions stop. This is the only way to see if the cleaning process is complete. Special preliminary measures should be performed before treatment, such as, looping the circuits and flow redirection for comprehensive system coverage and providing for a route for air or gas to escape both during and after the process.  Ideally, these issues should be addressed at the time of assembling of the hydraulic system when it is easier and less expensive. The functions performed by forced circulation, are as follows:
  • in the case of oxidation corrosion – removal of the inhibitor layer;
  • removal of grease from the internal surfaces of the pipelines;
  • removal of corrosion deposits after softening;
  • improvement of metal resistance to corrosion by passivation of pipe internal surfaces.
To determine the approximate time that will be required to complete the work and to choose the required chemicals, it is important to know the actual degree of corrosion in the pipes.  The amount of consumables needed will also depend on the size of the hydraulic system. It should be noted that the exact amount of chemicals required for cleaning the pipes can only be based on an estimate from past experience with the same or similar hydraulic systems. To assess the results of the chemical treatment of the pipes, a visual inspection of the most contaminated portions is required.  Not all particles however, will be visible to the naked eye.  This usually concerns small contaminants deposited on the bottom of the pipes.  Such particles are removed by flushing the pipes with oil.  Flow velocity should be at least 20 meters per second. Pipes are ususlly flushed with oil during assembly and during the start-up of oil-filled hydraulic systems. During the process, the presence of contaminants is controlled by a “granulometric analysis.”  If the flushing does not achieve the desired the results, a more thorough oil filtration of the oil may be required.  Granulometric control also allows the system to make decisions concerning the quality standards of the oil and the hydraulic system’s ability to meet purity requirements. To avoid the need to purity the oil often, it is best to use reliable equipment, capable of achieving the required results in the minimum time. These criteria are met by GlobeCore’s CMM system.  This plant performs thermal and vacuum purification of turbine oil, industrial oil, cable oil and other types of oil.  The process removes water, gases and solid particles.  Using the GlobeCore CMM unit can greatly extend the time between chemical cleaning and helps to keep the equipment in top running condition. See more video about transformer oil purification

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