Design and installation process for acetylene pipelines

Thread Content

Wofei Gas Supply System Knowledge Sharing: Design and Installation Process for Acetylene Pipelines. Acetylene is a dangerous gas that is frequently used in lighting, welding, and metal cutting (oxygen-acetylene flames), as well as in industrial processes such as the production of acetaldehyde, acetic acid, benzene, synthetic rubber, and synthetic fibers. Acetylene gas, when mixed with air or oxygen in a certain volume ratio, will explode upon exposure to fire. Acetylene gas reacts with many non-ferrous metals (copper, silver, mercury, zinc, cadmium, etc.) to produce explosive metal carbides, among which those formed with copper are highly explosive. Therefore, special attention must be paid to explosion prevention issues during installation and after the pipes are put into use for acetylene pipelines. Below, the editors from WoFei Technology will explain the design and installation process for acetylene pipelines. For acetylene pipelines, seamless steel pipes, stainless steel pipes, or steel-plastic composite pipes should be used. Meters, instruments, valves, and fittings for acetylene piping systems should be made of steel or cast iron; copper products shall not be used (copper alloys with a copper content of less than 70% may be used) ； The internal valve core and valve disc of the valve should be made of stainless steel or leather to ensure no sparks are generated when the valve is opened and closed. The gauge inspection box should be marked with the words “Acetylene” and “No Fire”. Laying and installation of acetylene pipelines: Acetylene pipelines are generally laid overhead or buried; laying them in trenches is not allowed. When laid underground, enhanced anti-corrosion treatment is required; manholes or those in other pipelines as well as ditches cannot be used, and it must not be buried in the same trench as water pipes, steam pipes, or electrical, lighting, and communication cables. Acetylene pipes have a small diameter, and are generally installed by manual burial. Overhead pipelines must be supported separately; it is strictly prohibited to install them together with gas, cable, and any other combustible gas pipelines. When installed alongside inert gases, water, and thermal pipelines, a certain distance should be maintained between them. Indoor overhead pipes should be installed along walls and columns, and insulation measures should be taken where the pipes are near heat sources or in areas where the temperature exceeds 70°C. Elevated pipelines are installed using self-propelled lifting machinery or by hand. The acetylene piping system is equipped with drains, purging ports, vent pipes, as well as lightning and static electricity protection grounding devices. Installation should be carried out only after the pipes have been fixed and verified to be correct according to the construction drawings. The pressure of acetylene gas is low; therefore, attention should be paid to the slope of the pipes during installation to prevent water accumulation inside the pipes from causing blockages. Acetylene pipeline connection: All external acetylene pipelines are welded using automatic track welding or TIG welding. When the pipeline is a steel-plastic composite pipe, flange connection is used. The connection between pipes and valves, as well as equipment and instruments, is achieved using flanges; in special cases, threaded connections may be used. When using threaded connections, polytetrafluoroethylene sealing tape should be used as a filler; lead-tin rosin hemp must not be used as a filler. Acetylene pipeline testing: After installation, acetylene pipelines shall undergo strength tests and tightness tests; the requirements for these tests are specified in the table. During the tightness test, a leak rate inspection is required. That is, after reaching the test pressure, apply soapy water to all connections to check for any air leaks. Any air leakage detected should be addressed promptly ； When there is no significant air leakage, the average hourly air leakage rate is calculated after a 24-hour pause; if it is not greater than 0.5%, the pipeline test is considered successful. Acetylene pipeline purging: After the pipeline test is successful, it must be purged with compressed air. Before introducing acetylene into the pipeline, it should be purged with dry nitrogen to remove the air from within the pipeline; at the end of the pipeline, it is considered acceptable if the oxygen content in the nitrogen gas discharged is below 3%. The tube must be filled with nitrogen when acetylene gas is passed through it. Fire sources must be prohibited from entering the site, and precautions against poison must be taken. The above is a detailed explanation provided by WoFei Technology regarding the design and installation process for acetylene pipelines. It is hoped that this will serve as a reference for manufacturers who need to carry out such design and installation work!