【Q&A】July 13, 2017

Common types include labyrinth seal, floating ring seal, mechanical face seal, water ring seal, and dry gas seal

1. Packing seal； 2. Soft packing seal ； 3. Mechanical seal 4. Spiral seal 5. Labyrinth seal 6. Jet seal 7. Floating ring seal 8. Auxiliary impeller seal 9. Sleeve seal 10. Magnetorheological fluid seal

There are packing seals and mechanical seals. Packing seals have the advantages of easy installation and maintenance, as well as low cost. However, its sealing performance is not very good. Mechanical seals have advantages such as good sealing performance and low likelihood of leakage, but they require high precision in installation and are expensive.

Contact-type steam seals: carbon ring steam seals, brush-type steam seals. Non-contact-type steam seals: labyrinth steam seals, honeycomb steam seals, Bledel steam seals

Packing seal, mechanical seal, labyrinth seal

The shaft seal provides a seal between the rotating pump shaft and the stationary pump casing, primarily to prevent high-pressure liquid from leaking out of the pump casing and to stop air from entering the pump. Common shaft sealing mechanisms for centrifugal pumps include: rubber seals with a skeleton, packing seals, mechanical seals, and floating ring seals. Their respective characteristics are as follows: (1) Rubber seals with a skeleton – This type of seal uses the elasticity of rubber and spring pressure to press the sealing sleeve tightly against the shaft (shaft sleeve). Its advantages are a simple structure, small size, and relatively good sealing performance ； The disadvantages are that the inner diameter of the sealed bowl tends to deviate from the specified values, the pressing force is too high resulting in high energy consumption; moreover, its heat resistance and corrosion resistance are inadequate, leading to a short service life, as well as strict installation requirements. (2) Packing seal: This type of seal generally consists of a packing gland, packing rings, and a packing compression nut. Sealing is achieved through the contact between the filler and the outer circular surface of the shaft (shaft sleeve), featuring a simple structure, low cost, and easy installation. The disadvantages are: high power consumption, severe wear of the shaft (shaft sleeve), which can lead to heating and smoking, and even burnout of the packing and shaft sleeve; it is not suitable for use with high-temperature, flammable, explosive, or corrosive media. (3) The mechanical seal (also known as face seal) consists of a rotating ring, a stationary ring, springs, a thrust ring, a drive seat, and sealing rings for the rotating and stationary rings. Sealing is achieved by the tight fit between the stationary and rotating rings, which creates a pressure seal. The advantages of mechanical seals are good sealing performance, long service life, low power consumption, and wide applicability. The disadvantages are complex manufacturing, high cost, and high installation requirements. (4) Floating ring seal: The floating ring seal achieves axial sealing through the contact between the floating ring and the end face of the floating sleeve.

The shaft seal provides a seal between the rotating pump shaft and the stationary pump casing, primarily to prevent high-pressure liquid from leaking out of the pump casing and to stop air from entering the pump. Common shaft sealing mechanisms for centrifugal pumps include: rubber seals with a skeleton, packing seals, mechanical seals, and floating ring seals. Their respective characteristics are as follows: (1) Rubber seals with a skeleton – This type of seal uses the elasticity of rubber and spring pressure to press the sealing sleeve tightly against the shaft (shaft sleeve). Its advantages are a simple structure, small size, and relatively good sealing performance ； The disadvantages are that the inner diameter of the sealed bowl tends to deviate from the specified values, the pressing force is too high resulting in high energy consumption; moreover, its heat resistance and corrosion resistance are inadequate, leading to a short service life, as well as strict installation requirements. (2) Packing seal: This type of seal generally consists of a packing gland, packing rings, and a packing compression nut. Sealing is achieved through the contact between the filler and the outer circular surface of the shaft (shaft sleeve), featuring a simple structure, low cost, and easy installation. The disadvantages are: high power consumption, severe wear of the shaft (shaft sleeve), which can lead to heating and smoking, and even burnout of the packing and shaft sleeve; it is not suitable for use with high-temperature, flammable, explosive, or corrosive media. (3) The mechanical seal (also known as face seal) consists of a rotating ring, a stationary ring, springs, a thrust ring, a drive seat, and sealing rings for the rotating and stationary rings. Sealing is achieved by the tight fit between the stationary and rotating rings, which creates a pressure seal. The advantages of mechanical seals are good sealing performance, long service life, low power consumption, and wide applicability. The disadvantages are complex manufacturing, high cost, and high installation requirements. (4) Floating ring seal: The floating ring seal achieves axial sealing through the contact between the floating ring and the end face of the floating sleeve.

Sealing sheets and sealing teeth come in smooth, labyrinth, and stepped types