【Q&A Question 232】2017.08.20

Liquid seal and gas seal. The liquid seal should handle high pressures and come with cooling. The gas seal is not clear

The commonly used sealing devices are stuffing seals and mechanical seals. Stuffing seals have a simple structure and are easy to maintain, but they offer poor sealing performance, have a short lifespan, and require frequent replacement. 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.

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 prevent air from entering the pump. Common shaft seal 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 tightening force is too high resulting in high energy consumption; furthermore, its heat resistance and corrosion resistance are inadequate, leading to a short service life, and strict installation requirements are necessary. (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 burn out 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 commonly used sealing devices are stuffing seals and mechanical seals. Stuffing seals have a simple structure and are easy to maintain, but they offer poor sealing performance, have a short lifespan, and require frequent replacement； A mechanical seal (also known as a face seal) consists of a rotating ring, a stationary ring, springs, a thrust ring, a drive seat, and sealing rings for both 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.

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 prevent air from entering the pump. Common shaft seal 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 tightening force is too high resulting in high energy consumption; furthermore, its heat resistance and corrosion resistance are inadequate, leading to a short service life, and strict installation requirements are necessary. (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 burn out 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. Reward

There are two types: packing seals and mechanical seals. Filler seals have a simple structure and are easy to maintain, but they offer poor sealing performance, a short lifespan, and require frequent replacement. Mechanical seals provide better sealing performance, a longer service life, and lower power consumption, although their structure is more complex and they are more expensive

Packing seals and mechanical seals: Packing seals are inexpensive, but their sealing performance is poor; mechanical seals offer good sealing performance, but they are costly and have a complex structure

Packing seal, mechanical seal, wear-resistant, corrosion-resistant

There are two types: packing seals and mechanical seals. The shaft sealing device ensures the proper and efficient operation of the centrifugal pump. During operation, the pump shaft rotates while the casing remains stationary; if the gap between them is not sealed or is poorly sealed, external air will penetrate into the low-pressure area at the center of the impeller, resulting in a decrease in the pump’s flow rate and efficiency. In severe cases, the flow rate can drop to zero due to air entrainment. Typically, mechanical seals or packing seals can be used to achieve sealing between the shaft and the casing.

The commonly used sealing devices are packing seals and mechanical seals. The packing seal has a simple structure and is easy to maintain, but it has poor sealing performance, a short lifespan, and requires frequent replacement ； Mechanical seals offer good sealing performance, a long service life, and low maintenance costs, but they have a more complex structure and are more expensive.