The mechanical and electrical engineering major of the first level construction engineer exam is an important section of industrial pipeline installation and cleaning. There are several cleaning methods for industrial pipelines:

1. Key points for water flushing implementation

1) Clean water should be used for water flushing. Flush stainless steel pipes, nickel and nickel alloy steel pipes, and the chloride ion content in the water shall not exceed 25ppm.

2) The water flushing flow rate shall not be lower than 1.5m/s, and the flushing pressure shall not exceed the design pressure of the pipeline.

3) The cross-sectional area of the water flushing discharge pipe should not be less than 60% of the cross-sectional area of the flushed pipe, and negative pressure should not be formed during drainage.

4) Water flushing should be carried out continuously. When there are no regulations in the design, it is considered qualified if the color and transparency of the water at the discharge outlet are consistent with the visual inspection of the inlet water. After the pipeline is washed with water and qualified, the accumulated water in the pipeline should be promptly drained and blown dry.

2. Key points for implementing air blowing

1) It is advisable to use large air compressors or large air storage tanks in production facilities for intermittent blowing. The blowing pressure shall not exceed the design pressure of the system container and pipeline, and the blowing flow rate shall not be less than 20m/s,

2) When purging oil pipelines, there should be no oil in the gas. During the blowing process, when there is no smoke or dust visible in the exhaust, a white cloth or white painted target plate should be set up at the exhaust port for inspection. After 5 minutes of blowing, if there is no rust, dust, moisture, or other debris on the target plate, it is considered qualified.

3. Key points for steam blowing implementation

1) Before blowing the steam pipeline, the insulation work of the pipeline system should have been completed.

2) The steam pipeline should be purged with high flow steam, with a flow rate of less than 30m/s. Before purging, the pipeline should be warmed up, drained in a timely manner, and the thermal displacement of the pipeline should be checked,

3) Steam blowing should be carried out in a cycle of heating, cooling, and reheating, and a method of blowing one pipe at a time and alternating blowing should be adopted

4. Key points for implementing oil cleaning

The lubrication, sealing, and control system oil pipelines of mechanical equipment should be flushed with oil before the system runs after the equipment and pipelines are pickled and qualified. Stainless steel oil pipelines should be cleaned with oil after steam blowing.

1) Oil cleaning should be carried out in a cyclic manner. Repeatedly raise and lower the oil temperature 2-3 times within 40-70 ℃ every 8 hours, and replace or clean the filter element in a timely manner;

2) When there are no regulations in the design or product technical documents, the pipeline oil should be cleaned and inspected using a filter screen.

3) After passing the oil cleaning, the pipeline shall be protected by sealing or nitrogen filling measures.

5. Key points for implementing chemical cleaning

The cleaning scope and quality requirements of pipelines that require chemical cleaning should comply with the provisions of the design documents.

1) When conducting chemical cleaning on pipelines, they should be isolated from unrelated equipment and pipelines

2) The formula of chemical cleaning solution should be tested and identified before use

3) The acid passivation of pipelines should be carried out in the order of degreasing and degreasing, acid washing, water washing, passivation, water washing, and oil-free compressed air drying. When acid washing is carried out in a cyclic manner, the pipeline should undergo air leak testing and hydraulic leak testing in advance to pass the inspection.

4) For pipelines that cannot be put into operation in a timely manner and pass chemical cleaning, closed or nitrogen filled protection measures should be taken.