Blasting purge, compressed air can also be used in this way!

Blasting purge, compressed air can also be used in this way!

After passing the strength test and before the air pressure tightness test, the steel pipeline should be washed and purged according to the requirements of GB50235-97 "Code for Construction and Acceptance of Industrial Metal Pipeline Engineering".

Over the years, water washing, air blowing, steam blowing and other technologies are mainly used for washing and blowing. This is more effective for small diameter pipelines, for large diameter pipelines often because the flow rate of the purge medium can not meet the requirements of the specified and can not reach the ideal purge effect. As pipeline accessories and instruments are more and more advanced, production technology and technical requirements continue to improve, some construction technology can not meet the requirements of construction. In the purging and flushing construction of large diameter steel pipeline, blasting purging method is replacing other construction methods previously used.

Blasting purge is to be blown one end of the pipe with much lower strength than the pipe blasting disc closed, the other end through compressed air. The air pressure in the system increases gradually, and when the ultimate pressure of the bursting disc is exceeded, the bursting disc suddenly breaks, and the compressed air in the system expands rapidly from the bursting hole at a high speed. At the same time, welding slag and other sundries in the pipeline are discharged under the impact of vibration and high-speed air flow caused by blasting. Repeated several times can meet the requirements of purge.

(1) The pressure test of the pipeline has been qualified, and the engineering quality has reached the provisions of the construction specifications and design documents;

(2) The purging scheme has been approved by the construction unit and supervision unit and mastered by the personnel involved in the purging;

(3) Orifice plates, flowmeters and valves that are not allowed to participate in the purge have been isolated, and the purge pipeline has been isolated from other adjacent pipelines and equipment;

(4) The choice of blasting system is very important, which is directly related to the cleanliness of the system and the efficiency of the purge. Generally, it should be divided according to the pipeline construction drawing and combined with the actual process flow, fully consider the impact of the force caused by blasting, reduce the temporary reinforcement points as much as possible, and facilitate the connection of the inlet pipe, installation of pressure gauge and replacement of blasting disc in the system. And there should be enough air capacity in the upstream of the system to ensure the purge quality of the upstream of the system;

(5) system is determined, the choice should be according to the actual pipeline installation blasting and its principle is that there must be enough space of blasting, blasting mouth generally should have more than 10 m space should be in the lowest parts of the pipeline, as far as possible choose the end of the pipe and easy to protection of the site, generally choose the level or downward direction, blasting mouth should have strong support;

(6) the bursting disc can use ordinary asbestos board, the thickness is generally 1~3mm, can draw "ten" words or "well" on the asbestos board, the bursting pressure is generally 0.3~ 0.4mpa, the pressure is too small to increase the number of blasting and the bursting disc is not easy to break, the pressure is too large and unsafe, prone to injury accidents.

Purge process characteristics and flow

The blasting blowing technology is used to carry out the blowing construction of large diameter steel pipeline, which has the following characteristics:

(1) high flow rate of purging medium (not less than 15m/s) with strong carrying force, can blow out the soil in the pipe, welding slag and pipe low-lying residual water and other sundries;

(2) High purge efficiency. For pipelines of the same specification and length, generally 4~6 times of blasting and blowing can meet the cleaning requirements;

(3) Due to the high speed of blasting air flow, not only rust and sundries are blown out. The debris in the dead corner of the pipeline will also be greatly improved by the rapidly expanding air flow belt due to the vibration during blasting;

(4) For large-caliber pipelines, it is difficult to find a suitable large gas source, and the quality is not easy to be guaranteed. Blasting purging is especially suitable for large-caliber pipelines;

(5) Compared with other washing and blowing methods, blasting blowing requires less equipment and means with less material (the main equipment is an air compressor, air source is atmosphere), saving labor and time, low cost, low technical requirements, and easy to popularize and apply;

(6) Medium and large diameter steel industrial pipelines with pipe diameter in the range of DN100~600mm can be used. Electric disc valve can also be used to replace bursting disc for steel pipe with diameter less than DN200mm using this blowing technology. The same effect can be achieved with bursting blowing by quickly opening and closing the valve.

Purge process flow

Determine the purge system → install temporary blind plate (isolate devices and systems that cannot be blown) → install pressure gauge (temporary reinforcement of local pipelines and pipe frames) → open all valves in the system → install bursting disc → charge → blasting → quality inspection and shooting (repeat the installation of bursting disc if unqualified) → acceptance.