General Analysis Of Technical Knowledge Of Mechanical Seals

1. Improve machine efficiency and reduce energy consumption.

1. Reduce internal leakage, external leakage and penetration of the machine, and improve the volumetric efficiency of the machine. For example, Daqing Refinery changed the impeller mouth ring of the coking 5FDJ5×2 centrifugal pump to a mechanical seal, which increased the pump efficiency by 3.6% to 5.6%.

2. Reduce friction loss and improve the mechanical efficiency of the machine. For example, changing the double-end seal to a single-end seal, changing the unbalanced type to a balanced type, and closing one end of the double-supported reduced-bottom pump (the so-called head-cutting pump) can reduce friction loss and improve mechanical efficiency.

3. Change the sealing method to improve the efficiency of the machine or unit. For example, changing the shielded pump to a mechanical seal pump can improve the efficiency of the motor; using a magnetic transmission pump can improve the efficiency of the machine.

4. Change the auxiliary system to reduce energy consumption and improve the efficiency of the unit. For example, the hot oil pump self-flushing is changed to a small impeller circulation flushing; the double-end seal is changed to a single-end seal to save energy consumption in the sealing oil auxiliary system.

2. Save raw materials. For example, process fluid recovery, reducing or eliminating the loss of power steam and process fluid, reducing seal oil loss, etc.

3. Improve machine reliability. For example, the leakage and life of the shaft seal determine the reliability of the shaft seal and the machine.

4. Safety and environmental protection. According to a survey report of a Japanese factory, 32 of the 786 accidents were caused by leakage (accounting for 42%). In addition, process fluid leakage will also cause environmental pollution, including air pollution, water pollution and workshop environmental pollution.

The significance of mechanical seals

1. Although sealing technology is not a leading technology, it is a decisive technology. For example, the Challenger space shuttle of the United States fell due to a sealing accident; the circulating pump of the nuclear power plant was changed from a shaft seal pump to Sanitary Rotary Lobe Pump for safety and reliability. After the mechanical seal was improved, it was changed back from a shaft seal pump to a shaft seal pump due to reliable work, thereby improving the efficiency of the motor. These two things fully illustrate that although mechanical seals are not leading technologies, they are decisive technologies.

2. Although the seal is not big and is just a component, it can determine the safety, reliability and durability of the machine equipment. The shaft seal in the pump kettle of the petrochemical plant is not big. Once a product leakage accident occurs, it will not only affect the operation of the pump equipment, but also cause combustion or explosion, resulting in shutdown of the process equipment and personal injury.

3. Mechanical seals account for about 50% of the workload in daily maintenance of equipment such as pumps and kettles. Through surveys of several petrochemical companies at home and abroad, it is shown that in daily maintenance of equipment such as pumps and kettles, the maintenance workload of mechanical seals accounts for almost 50%. About 70% of the maintenance costs of centrifugal pumps are due to seal failures.

Status of mechanical seals

According to the survey, more than 86% of the pumps in petrochemical process units use mechanical seals. With the development of mechanical seal technology, mechanical seals will occupy a more important position in pumps.