Pressure pipelines

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I. Definition of pressure pipelines
According to the catalog of special equipment, a pressure pipeline is a tubular device that operates under certain pressure to transport gases or liquids. The scope of application is defined as follows: ① the maximum operating pressure is greater than or equal to 0.1 MPa (gauge pressure); ② the medium being transported is gas, liquefied gas, steam, or a liquid that is flammable, explosive, toxic, corrosive, and whose maximum operating temperature is higher than or equal to its normal boiling point; and ③ the nominal diameter of the pipeline is greater than or equal to 50 mm. Except for pipes with a nominal diameter of less than 150 mm and a maximum operating pressure of less than 1.6 MPa (gauge pressure), as well as the pipes that form part of the equipment used for transporting non-toxic, non-flammable, and non-corrosive gases. Among them, the safety supervision and management of oil and gas pipelines shall also be carried out in accordance with laws and regulations such as the Work Safety Law and the Oil and Gas Pipeline Protection Law. By definition, first: gauge pressure ≥ 0.1 MPa ； Second: The medium must meet the requirements ； Third: ≥DN50mm ； All three conditions must be met simultaneously in order for it to be classified as special equipment. However, there is an exception: this does not apply to pipes and the piping associated with equipment for non-toxic, non-flammable, and non-corrosive gases with a diameter of <DN150mm and a gauge pressure of <1.6MPa. Let’s take an example: suppose there is a pipeline with a DN128 diameter in a compressed air power station; its gauge pressure is less than 1.6 MPa, and the medium flowing through it is compressed air. In this case, it does not qualify as a special equipment. If a parameter is changed, such as the pipe diameter going from DN128 to DN150, then it becomes a special equipment. So, everyone should pay attention when making the decision. II. Inspection of pressure pipelines is carried out in accordance with the \"TSG 31—2025 - Safety Technical Regulations for Industrial Pipelines\"; here we are referring only to industrial pipelines, as most enterprises do not have facilities for other types of pipelines such as long-distance pipelines and utility pipelines. Pressure pipelines generally undergo their first periodic inspection within 3 years after being put into service. The subsequent inspection intervals shall be determined by the inspection agency based on the pipeline safety status level, in accordance with the following requirements: (1) For pipelines with a safety status level of 1 or 2, GC1 and GC2 class pipelines generally require inspection no more often than every 6 years, while GC3 class pipelines require inspection no more often than every 9 years ； (2) For those with a safety status rating of level 3, inspections are generally carried out no more than once every 3 years; during their period of use, the entity using them shall implement effective monitoring measures for the pipelines ； (3) For pipelines with a safety status rating of level 4, the user entity must address the pipeline defects; otherwise, they shall not continue to use them. Inspection of safety accessories and instruments: (1) Whether the safety valve is within its valid calibration period ； (2) Are the burst disc devices replaced on schedule? ； (3) Is the emergency shut-off valve in good condition? ； (4) Is the pressure gauge within its calibration validity period (applicable to pressure gauges that require calibration?). III. Annual inspection of pressure pipelines 1. Annual inspection of pressure pipelines: That is, regular self-inspections, which involve the operating entity checking whether there are any conditions that could affect the safe operation of the pipelines under normal operating conditions; such inspections should be carried out at least once a year. 2. The annual inspection can be carried out by safety management personnel of the using unit, who assign professionally trained personnel to do it, or it can be entrusted to an inspection agency qualified for regular inspections of industrial pipelines. 3. The annual inspection shall include, at a minimum, inspections of the pipeline safety management, the operating condition of the pipeline, and its safety accessories and instruments. When necessary, wall thickness measurements and resistance value measurements should also be conducted.