Nitrogen purge pipe diameter

The pipes are a bit large; it is recommended to use water for flushing or to employ explosive cleaning. Below are some key points: Attention should be paid to safety since nitrogen is used as the gas source, in order to avoid the risk of suffocation. The pressure must not exceed the design pressure of the pipes; it is advisable to keep it between 0.3 and 0.4 MPa, as exceeding 0.6 MPa can be dangerous. For explosive cleaning, steel pipes, after passing the strength tests and before undergoing pressure integrity tests, must be flushed and cleaned in accordance with the requirements of GB50235-97 \"Code for Construction and Acceptance of Industrial Metal Piping Projects\". For many years, techniques such as water flushing, air purging, and steam purging have been primarily used for flushing and purging. This is quite effective for small-diameter pipes; however, for larger-diameter pipes, the ideal purging effect is often not achieved because the flow rate of the purging medium does not meet the specified requirements. As pipeline fittings and instruments become more advanced, the technical requirements for production processes continue to rise, and some construction techniques are no longer sufficient to meet these requirements. In the cleaning and flushing of large-diameter steel pipes, the blasting cleaning method is replacing other methods that were used in the past. Blasting purging involves sealing one end of the pipeline to be purged with a blast disc whose strength is much lower than that of the pipeline, while compressed air is introduced at the other end. The air pressure within the system gradually increases; once it exceeds the maximum pressure that the rupture disc can withstand, the disc ruptures suddenly, and the compressed air in the system expands rapidly and is ejected at extremely high speeds through the rupture opening. At the same time, the slag and other debris inside the pipeline are also expelled as a result of the vibrations caused by the blasting and the impact of high-speed air currents. Repeating this process several times will meet the purging requirements. Preparatory work and construction requirements for blasting purging: (1) The pressure test of the pipelines has been successful, and the quality of the work meets the requirements specified in the construction standards and design documents ； (2) The purging plan has been approved by the project owner and the supervision unit, and is available for those involved in the purging process to refer to ； (3) Orifice plates that are not allowed to be involved in the purging process. Flow meters, valves, etc. have been isolated, and this purging pipeline has also been separated from other adjacent pipelines and equipment ； (4) The selection of the blasting system is very important, as it directly affects the cleanliness of the system cleaning process as well as the efficiency of that process. Generally, the division should be based on the pipeline construction drawings along with the actual process flow. Full consideration should be given to the effects of forces caused by blasting. Temporary reinforcement points should be minimized as much as possible to facilitate the connection of intake pipes within the system, the installation of pressure gauges, and the replacement of blast valves. Moreover, there should be sufficient air capacity upstream of the system to ensure the quality of purging in that area ； (5) Once the system is determined, the blasting site should be selected based on the actual installation location of the pipeline. The principle is that there must be sufficient space for blasting. There should generally be at least 10 meters of open space at the blasting site; it is advisable to choose the lowest point of the pipeline, preferably at one of its ends in a location that is easy to protect. The blasting direction is usually horizontal or downward, and the blasting site must have sturdy supports ； (6) Ordinary asbestos sheets can be used for burst discs, with a thickness of generally 1–3 mm. A “+” or “X” pattern can be marked on the asbestos sheet; the burst pressure is usually between 0.3–0.4 MPa. If the pressure is too low, the number of times the disc bursts increases and it is difficult for the disc to break, while if the pressure is too high, it becomes unsafe and can lead to injuries. Process characteristics and procedures for purging: The blasting purging technique is used for purging large-diameter steel pipelines, and it has the following characteristics: (1) The flow rate of the purging medium is high (not less than 15 m/s), giving it strong carrying capacity; this allows it to remove soil, weld slag, residual water in low-lying areas of the pipeline, as well as other debris from within the pipeline ； (2) High purging efficiency. For pipelines of the same specification and length, 4 to 6 blasting and purging cycles are generally sufficient to meet the cleanliness requirements ； (3) Due to the high speed of the blasting purge airflow, not only rust and debris are blown out. Debris in the dead corners of the pipelines is also carried away by the rapidly expanding airflow due to the vibrations during blasting, resulting in a significant improvement in the cleaning quality ； (4) For large-diameter pipes, it is difficult to find a suitable air source of sufficient capacity, and the quality of such air sources cannot be guaranteed; blast cleaning is particularly suitable for large-diameter pipes ； (5) Compared with other flushing and purging methods, blast purging requires less equipment and materials (the main equipment is an air compressor, with atmospheric air as the gas source), it saves labor and time and reduces costs; it also has low technical requirements, making it easy to implement on a wider scale ； (6) Medium and large-diameter steel industrial pipes with a diameter in the range of DN100~600 mm can all be used. When this purging technique is used for steel pipelines with a diameter of less than DN200 mm, an electric disc valve can also be used in place of a rupture disc; by quickly opening and closing the valve, the same effect as purge cleaning using a rupture disc can be achieved.