Pump packing seal and Mechanical seal for kettle Difference and selection of

The shaft seal is a sealing device set to prevent leakage at the pump shaft and housing. The commonly used shaft seals include packing seal, mechanical seal and power seal.

The shaft seal of the reciprocating pump is usually a packing seal. When the medium is not allowed to leak, the diaphragm reciprocating pump can be used. The shaft seal of rotary pump (including vane pump, rotor pump, etc.) mainly includes packing seal, mechanical seal and power seal.

1. Packing seal

The packing seal is simple in structure, cheap in price and convenient in maintenance, but it has large leakage and power loss. Therefore, the packing seal is used to transport general media, such as water: it is generally not suitable for petroleum and chemical media, especially for valuable, explosive and toxic media.

2. Mechanical seal

Mechanical seal (also called face seal) has good sealing effect, small leakage, long service life, but high price, and higher requirements for processing, installation and maintenance than general seals. Mechanical seal is suitable for conveying petroleum and chemical media, and can be used for various media with different viscosity and strong corrosiveness containing particles. The American Petroleum Institute logo stipulates that, unless otherwise specified by the user, it shall be equipped with Cartridge mechanical seal ，

3. Power seal

The power seal can be divided into two types: back blade seal box and auxiliary impeller seal. When the pump is working, the centrifugal force of the back vane (or auxiliary impeller) is used to reduce the medium pressure at the shaft seal to the normal or negative pressure state, so that the pump will not leak during use. When stopping, the centrifugal force disappears, and the sealing function of the back blade (or auxiliary impeller) fails. At this time, the sealing device is used for sealing.

Packing seal is often used in the parking seal device matched with the back blade (or auxiliary impeller). There are two types of packing seal: ordinary type and mechanical elastic type. The ordinary packing seal is similar to the ordinary packing seal pump. It requires a slight positive pressure at the shaft seal to avoid dry friction of the packing. The mechanical elastic packing stop seal uses counterweight to loosen the packing when the pump is running, and the packing is compacted when the pump is stopped.

In order to ensure the service life of the shutdown sealing device and reduce the leakage, there should be restrictions on the inlet pressure of the power seal pump, namely:

Where Ps - pump inlet pressure, MPa:

Pd pump inlet pressure, MPa

The power seal is reliable, the price is cheap, and the maintenance is convenient. It is suitable for conveying media containing more solid particles, such as slurry and slurry pump in the phosphoric acid industry. The disadvantage is that the power loss is larger than that of mechanical seal, and the service life of its shutdown seal device is shorter.

The shaft seal is a sealing device set to prevent leakage at the pump shaft and housing. The commonly used shaft seal types include packing seal, mechanical seal and power seal. The shaft seal of reciprocating pump is usually a packing seal. Diaphragm reciprocating pump can be used when conveying medium without leakage. The shaft seal of rotary pump (including vane pump, rotor pump, etc.) mainly includes packing seal, mechanical seal and power seal