c Pressure-sealing operation refers to a non-standard construction carried out to seal leaky fluid medium pipelines or equipment while the device facilities are in continuous production and operation. This means that workers have to operate in an environment where high temperatures, high pressure, flammable and explosive, and toxic and harmful energy media are not isolated. This technology is like a "minimally invasive surgery", which can eliminate the leakage隐患 while avoiding the huge economic losses caused by the complete shutdown of the equipment. However, the process is like walking on the edge of a cliff. According to the analysis by the emergency management department, if there is no strict and standardized management, it is highly likely to cause serious accidents such as fire explosions, poisoning and suffocation. 01 Work Risk: Hidden Challenges in Construction Operations The reason why pressure sealing is classified as a high-risk operation lies in its inherent multiple uncertainties. The construction objects are usually pipelines or equipment that carry flammable, explosive, toxic, harmful or high-temperature and high-pressure media. During the construction process, these energy media are not isolated, and the on-site conditions are complex and constantly changing. Specifically at the construction level, numerous problems arise. In oilfield operations, common issues include inaccurate sealing positions in the tubing and poor sealing effectiveness. In gas well maintenance, complex situations such as stuck drill pipes, improper seating of bridge plugs, and corrosion perforation of the pipe string may be encountered. For tight gas horizontal wells, there are also technical challenges such as failure of tubing column sealing and pressurized top-down unthreading of multiple tubing strings. Behind these technical challenges lies a serious safety issue. Experts from the Emergency Management Department of Shandong Province pointed out that many chemical accidents that occurred in China in recent years were directly related to pressure-sealing operations. If the operation is incorrect, the leaked medium may trigger a chain reaction, leading to disastrous consequences. Core principle: Safe retreat and the "Ten Do Not Block" red line When dealing with high-risk operations, it is crucial to establish clear safety principles. In the guideline issued by the Emergency Management Department of Shandong Province in 2024, the fundamental principle of "adhering to safety retreat" was clearly stated. This means that when a leakage occurs in the equipment, the enterprise should first consider taking conventional measures such as withdrawing materials and halting production, in order to fundamentally eliminate the potential hazard. Pressure-sealing is only a last resort and not the preferred option. Based on this principle, the competent authorities have clearly delineated ten absolutely unbreakable "red lines", which are known as the "Ten Do-Nots" for pressure-sealing operations: · Insufficient on-site safety conditions: Work should not be carried out when the on-site conditions do not meet the requirements for safe construction or there is no safety guarantee. · Structural strength cannot be evaluated: It is impossible to measure the wall thickness of the sealing area and operations should not be carried out when material cracks are expanding. · The sealing foundation is not stable: If the bolt strength is insufficient and cannot be reinforced, or if the flange seal does not meet the requirements, work should not be carried out. · Parameter exceeds the specified range: Operations should not be carried out when the pressure and temperature parameters are beyond the applicable range as defined by industry standards. · Impact on safety release function: Operations should not be carried out if they may affect the functions of safety devices such as safety valves and rupture discs. · The root cause has not been resolved: Operations should not be carried out when leakage occurs due to vibration or pipe system stress and cannot be eliminated. · The medium is extremely dangerous: Operations should not be carried out when there is a leakage of extremely hazardous medium. · Multiple leaks in the same pipeline: When there are already two pressurized sealing points on the same pipeline, a third sealing point should not be added. These prohibitive provisions are formulated based on a comprehensive analysis of numerous accident lessons and serve as the fundamental guarantee for ensuring operational safety. 03 Preparatory Work for Construction: A Seamless System of Preparation Comprehensive pre-construction preparations are the most effective step in reducing the risks associated with pressure sealing. This stage requires completing the entire process from risk identification to scheme approval. Accurate risk identification and assessment is the first step. Enterprises need to accurately identify all safety risks in pressure-sealing operations and formulate corresponding control measures. In oilfield operations, this means analyzing potential sealing challenges in advance; in the chemical industry, special attention should be paid to the physical and chemical properties of the medium and its potential hazards. The meticulous formulation and approval of the plan are the technical guarantee. The construction plan must be formulated in accordance with national standards such as "Technical Specification for Pressure Sealing of Pressure-bearing Equipment" (GB/T 26467). For ultra-high pressure pipelines, an innovative "superimposed sealing" method can be adopted, which divides the once extremely high pressure sealing into multiple high-pressure sealings, significantly reducing the risk of a single operation. Strict qualification reviews for construction units and personnel are a guarantee of talent. Construction units must possess the required qualifications, and workers need to undergo professional training. Specialized workers must hold certificates to work. Experience shows that the direct cause of many accidents is the lack of necessary professional technical capabilities among workers. 04 Technical Plan: Scientific Selection and Innovative Process Application Choosing the appropriate sealing technology is the key to solving on-site problems. The main technologies in the industry can be divided into two categories: injection sealing and fastening sealing. Among them, the injection sealing method includes various methods such as fixture injection and steel band binding injection. For different scenarios, it is necessary to flexibly apply innovative techniques: In the extraction boreholes of high-gas coal mines, the Shirhe Mine in Shanxi Province upgraded the traditional "two walls and one injection" process to "three walls and two injections", and adopted a new type of nano diffusion expansion agent, enabling the boreholes to achieve the effect of "high concentration and long-term extraction". This process also has the ability to replenish slurry for leak sealing, and can effectively deal with abnormal concentration drops. In the treatment of pressure in the annular space of low-temperature shallow gas wells, technicians innovatively proposed the process sequence of "one flushing, two blocking, and three sealing".