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1. Standards for implementation: The design, manufacture, and modification of high-risk pump seals and systems shall comply with the following standards: (1) API682-2004 \"Shaft Seal Systems for Centrifugal and Rotary Pumps\"； (2) API610-2004 \"Centrifugal Pumps for the Oil, Petrochemical, and Natural Gas Industries\" ； (3) GB150.1~150.4-2011 \"Steel Pressure Vessels\" ； (4) ASME (or ANSI) B16.5-2003 \"Pipe Flanges and Flanged Fittings\" ； (5) SH3406-1996 \"Steel Pipe Flanges for Petrochemical Industry\" ； HG/T 20615-2009 \"Steel Pipe Flanges CLASS Series\" ； (6) SHT3156-2009 \"Technical Specifications for Shaft Sealing Systems Used in Petrochemical Centrifugal Pumps and Rotary Pumps.\" 2. Recommendations for seal selection 2.1 Selection of seals for high-temperature hot oil 2.1.1 Basic requirements for selection Seals for high-temperature hot oil pumps should be double-end face seals of the back-to-back, face-to-face, or face-to-back pressurized type as specified in API682-2004 (arrangement type 3); in special cases, double-end face seals of the face-to-back unpressurized type (arrangement type 2) can be considered. 2.1.2 Selection of flushing scheme (1) For high-temperature hot oil pumps, the dual seals can be selected as P21(23, 32)+53A(B), P21(23, 32)+54, or P21(23, 32)+74, depending on the actual conditions on site ； The P02 flushing option can be added depending on the temperature of the sealing chamber and the requirements of the sealing design ； The pressure-free dual-seal structure (i.e., the P52 scheme) must ensure the safety of emissions. (2) If the medium contains solid particles that can easily damage the seal, and oil sealing is possible on-site, external flushing with P32 is recommended ； (3) For media that are relatively clean, P21 (23) self-cleaning or P32 external flushing can be used ； (4) For media with high viscosity at room temperature and where oil sealing conditions are not available on-site, it is recommended to use P02 to lower the temperature of the sealing chamber ； The double seal should be a pressurized double seal. (5) For easy coking of the outer seal, it is recommended to add the P62 solution. 2.1.3 Selection of sealing type and material (1) For high-temperature pump seals, metal bellows resistant to high temperatures are recommended; the type of metal bellows to be used should be chosen based on the corrosive properties of the medium and the operating temperature ； The auxiliary sealing element should use flexible graphite or high-temperature resistant perfluoroether rubber depending on the temperature ； (2) The graphite rings should be made of high-quality blister-resistant graphite ； 2.1.4 Technical requirements and precautions (1) For the P02 scheme, it is recommended to use low-pressure steam for cooling; for P21 and P23, softened water is advised. It is necessary to ensure an adequate amount of cooling water as well as an appropriate flow rate. The inlet temperature of the cooling water should be below 32°C, while the outlet temperature should be below 49°C℃ ； (2) The P32 system requires the installation of check valves, pressure gauges, and flow control valves; (Y-type filters, flow meters) are optional items ； (3) When using P53, P54, or P74, the medium-side seal must be able to withstand pressure in both positive and negative directions; the atmosphere-side seal should also use a high-temperature resistant seal identical to that used on the medium-side seal ； For those that already use P52, the atmospheric side seal should be a seal capable of withstanding the temperature and pressure on the medium side ； (4) If the P52 scheme is adopted, the liquid storage tank should be equipped with high and low liquid level alarms; its top discharge outlet shall be fitted with a flow-limiting orifice plate and a check valve (optional, depending on requirements). For the P52 flushing scheme, the discharge system must have a special design to prevent the leakage of high-temperature, flammable materials from causing hazards ； (5) If a mature 2CW-CS design that complies with API682 standards is selected based on actual conditions, its flushing and discharge systems shall have special designs and alarms to prevent the leakage of high-temperature flammable media from causing hazards ； (6) For the P62 protocol, low-pressure dry steam or nitrogen is recommended (nitrogen is used only in non-enclosed areas to prevent harm to personnel). When using low-pressure dry steam with P62, it is necessary to control the flow rate appropriately and be careful to prevent the steam from contaminating the lubricating oil in the bearing area ； (7) The liquid storage tank should be of an elongated shape; depending on the shaft diameter, the standard liquid level volume is 12 L (for shaft diameters of 60 mm or less) and 20 L (for shaft diameters greater than 60 mm). The material used should be 304 or 316 ； Schemes P52 and 53 are equipped with manual fluid infusion pumps ； (8) If the quality of the water used for system cooling is poor, it is recommended to use an external, separate cooler for the isolation (buffer) fluid cooler, as this facilitates cleaning and improves the cooling effect ； The selection and installation of the cooler must facilitate exhaust ventilation, in order to avoid air blockages that could affect the circulation of the isolation (buffer) fluid ； (9) The piping of the sealing system should be arranged reasonably to facilitate the circulation of the medium, ease maintenance, prevent people from stepping on it, and avoid leaks of the medium ； (10) When designing the seal body, it is necessary to ensure that the seal can operate at the temperature of the medium, so as to guarantee that in the event of an unexpected interruption in the auxiliary system, the seal can continue to function properly for at least 8 hours ； (11) All external seals shall ensure normal operation for not less than 8 hours in the event of a leak in the internal seal. 2.1.5 Selection of isolation fluid: For high-temperature pumps, heat transfer oil/heat-resistant white oil is recommended; products that are not prone to coking at high temperatures should be chosen. 2.1.6 Alarm System (1) The P52 design includes alarms for pressure as well as high and low liquid level levels ； (2) The P53A system is equipped with pressure and low liquid level alarms ； (3) The P53B setup is equipped with a pressure alarm ； (4) The P74 model is equipped with pressure and flow alarms ； (5) Systems with a 2CW-CS sealing structure shall be equipped with necessary and reliable alarms ； (6) The alarm system should incorporate a DCS. 2.2 Selection of Seals for Light Hydrocarbon Medium Pumps 2.2.1 Basic Requirements for Selection For high-risk pumps handling light hydrocarbons, it is recommended to use a double seal without pressure faces in accordance with API682-2004 (arrangement type 2) or a double seal with pressure (arrangement type 3). 2.2.2 Selection of flushing scheme (1) For operating conditions in which there is a sufficient margin between the pressure in the sealing chamber and the vaporization point of the medium at the operating temperature, the back-to-back pressure-free scheme P52 can be used (with a discharge system connected to the top of the buffer tank), or P72+76 (75) ； (2) For operating conditions in which the pressure in the sealing chamber is close to the vaporization point of the medium at the operating temperature, and where there are no emission requirements on site, the pressurized dual-seal solutions P53 B (A/C), P54, or P74 should be selected ； (3) A self-cleaning scheme is employed depending on the medium temperature: P11/P13/P14, P21. 2.2.3 Selection of sealing type and material (1) Selection of sealing structure: Type A seal ； (2) Materials with low frictional heat generation and good thermal conductivity are suitable for use as pairing materials in friction pairs ； (3) Select different sealing materials based on the corrosivity of the medium. 2.2.4 Technical requirements and precautions (1) For seals used in transporting media with high hydrogen sulfide content, perfluoroether rubber is recommended as the auxiliary sealing material ； (2) Emissions from the P52 and P75, P76 systems should be routed to the flare system ； (3) When the internal seal of all flushing schemes leaks, its external seal shall be able to function properly for no less than 8 hours ； (4) The liquid storage tank should be of an elongated shape; depending on the shaft diameter, the standard liquid level volume is 12 L for shaft diameters of 60 mm or less, and 20 L for shaft diameters greater than 60 mm. The material used should be 304 or 316 ； Schemes P52 and 53 are equipped with manual fluid infusion pumps ； (5) If the quality of the water used for system cooling is poor, it is recommended to use an external, separate cooler for the isolation fluid cooler, as this facilitates cleaning and improves the cooling efficiency ； The selection and installation of the cooler must facilitate exhaust operation, to prevent air blockages that could affect the circulation of the isolation fluid ； (6) The piping of the sealing system should be arranged properly to facilitate the circulation of the medium, ease maintenance, prevent people from stepping on it, and avoid leaks of the medium ； (7) The P52 and P72+75(76) configurations are connected to the discharge system and require flow-limiting orifice plates (check valves can be used as needed); attention should be paid to the back pressure of the discharge system as well as the impact of the medium on the sealing system. 2.2.5 Selection of isolation fluid (1) For light hydrocarbons, low pour-point industrial white oil is recommended as the isolation fluid; different pour points are chosen depending on the ambient temperature to ensure proper performance in outdoor use during winter ； (2) When using a low-viscosity lubricant, it should not contain antioxidants or anti-wear agents. 2.2.6 Alarm System (1) The P52 design includes alarms for pressure as well as high and low liquid level levels ； (2) The P53A system is equipped with pressure and low liquid level alarms ； (3) The P53B setup is equipped with a pressure alarm ； (4) The P75 (76) model is equipped with a pressure alarm; the P75 should also be equipped with a level alarm ； (5) The alarm system should incorporate a DCS. 2.3 Selection requirements for seals of pumps handling toxic and hazardous media 2.3.1 Basic selection requirements Seals for pumps handling toxic and hazardous media should adopt a pressurized dual-seal design in accordance with API682-2004 (arrangement type 3). When the operating temperature exceeds 176°C (350°F), a Type C seal should be used, provided that it is specifically designed for such purposes. 2.3.2 Selection of flushing scheme (1) P53B (A), P54, or P74 are recommended ； (2) Flush plans P11, P21, P23, or P62 are used as supplementary measures depending on the medium temperature ； (3) Select seals of different materials based on the corrosiveness of the medium. 2.3.3 Selection of sealing types and materials: For high-temperature applications, refer to 2.1.3; for low-temperature applications, refer to 2.2.3. 2.3.4 Technical requirements and precautions (1) For sealing rings in aromatic medium, perfluoroether rubber is recommended as the material ； (2) Other technical requirements and precautions: For high temperatures, refer to 2.1.4; for low temperatures, refer to 2.2.4. 2.3.5 Selection of isolation fluid: Refer to 2.1.5 for high-temperature applications and 2.2.5 for low-temperature applications. When an oil-based isolation fluid is incompatible with the medium, it may be necessary to choose a different suitable isolation fluid. 2.3.6 Alarm system: High temperature is the same as 2.1.6, and low temperature is the same as 2.2.6. 2.4 Selection of single-face seals for pumps that do not meet the conditions for modification: For high-risk pumps whose pump seal chamber dimensions cannot be modified to accommodate dual-seal arrangements, the pump’s cover can be replaced to achieve the required seal chamber dimensions ； It can also be upgraded by updating the pump type. For high-risk pumps that truly cannot undergo dual-seal modification, a highly reliable single-end face seal should be used, along with additional leakage detection and alarm systems (P65, P66). Prevent major leakage accidents from occurring.