What should the process of initial purging for liquid ammonia pipelines be like?

The initial purging of the liquid ammonia pipeline should proceed in the same way as the purging of other pipelines. If rust remains on the inner walls of the pipeline after purging is complete, further purging should be carried out until the pipeline is completely clean.

If it is just a simple pipe placed in the atmosphere, I recommend filling it with N2 at a slight positive pressure as a protective measure, which will greatly reduce the likelihood of rusting.

Reply to 2# Yan Qiusheng: If it’s not completely removed, is pickling needed?

Piping purging and cleaning: 1. After the piping system has passed the strength test, and prior to the pneumatic tightness test, purging and cleaning should be carried out section by section. 2. The purging method should be determined based on the usage requirements of the pipeline, the working medium, and the degree of dirt on the inner surface of the pipeline. The sequence of purging should generally be in the order of main pipes (by section), branch pipes, and drain pipes. 3. Before purging, the instruments in the system should be protected, and the plate orifice plates, ring orifice plates, and control valves in the system should be removed; the pipes should be connected using ring plates and temporary short tubes. The valves installed at the upstream end should also be removed; after cleaning for a period of time that meets the specified requirements, the valves should be reinstalled, and then cleaning should continue for the second and third sections. The purging of each branch pipe can be carried out within each purging section, but it can also be performed separately. The valves at the ends of each branch pipe should also be removed before cleaning. Once the entire system has been purged, reset the orifice plates, control valves, and end valves. 4. Equipment and pipelines that are not allowed to be purged should be isolated from the purification system. 5. For pipes that cannot be cleaned by blowing or may still have contaminants left after such cleaning, other methods should be used for purification to meet the requirements specified for cleaning by blowing. 6. During purging, dirt from the pipes must not enter the equipment, and dirt expelled by the equipment must not enter the pipes either. 7. The pipeline purging should have sufficient flow rate; the purging pressure must not exceed the design pressure, and the flow velocity must not be lower than the operating flow velocity, which is usually not less than 20 m/s. 8. During cleaning, except for non-ferrous metal pipes, a hammer should be used to tap the pipes (copper or wooden hammers can be used for non-ferrous metals); special attention should be paid to tapping the welds, the bottom of the pipes, and hard-to-reach areas, but the pipes and fittings must not be damaged. 9. Before purging, the stability of the pipe supports and hangers should be considered, and reinforcement measures should be taken if necessary. 10. After the pipeline cleaning is completed successfully, aside from the specified inspection and restoration tasks, no other activities that could affect the cleanliness inside the pipeline shall be carried out, and the \"Pipeline System Cleaning (Degreasing) Record\" must be filled out.