Structural Features and Types of Mechanical Seals

Ⅰ. There are many different types of mechanical seals

1. According to the logarithm of the sealing end face, it is divided into single end face, double end face and other mechanical seals

(1) Single end face: Only one pair of sealing end faces is required in the sealing device. It has a simple structure and is a commonly used mechanical seal type.

(2) Double end face: There are two pairs of sealing end faces in the sealing device. Its structure is complex, suitable for strong  corrosion, flammable assembly type mechanical seal explosive, toxic and harmful media and vacuum occasions.

2. According to the function of sealing fluid, it is divided into balanced and unbalanced mechanical seals

(1) Balanced type: The sealing fluid acts on the seal face and presses the import mechanical seal force to partially unload or fully unload.

(2) Non-balanced type: The pressure of the sealing fluid acting on the sealing end face is not unloaded.

Balanced type is suitable for medium and high pressure mechanical seal, while non-balanced type is suitable for low pressure mechanical seal.

3. According to whether the spring is placed in the sealing fluid, it is divided into spring built-in and spring external mechanical seals

(1) spring built-in type: The spring is placed in the sealing fluid.

(2) spring external type: The spring is placed outside the sealing fluid.

The sealing end face of spring built-in type is in a good stress state with small leakage and good cooling, lubrication. Therefore, in addition to corrosive media, the built-in structure should be used as much as possible.

4. According to the number of springs in the compensation structure, it is divided into single-spring and multi-spring mechanical seals

(1) Single-spring type: Only one spring is required in the compensation structure used for light loads and small shaft diameters.

(2) Multiple-spring type: There are multiple springs in the compensation structure for larger shaft diameters. The distribution of the spring force on the sealing end face is relatively uniform, but the diameter of the spring wire is small, and the corrosion has a great influence on the spring.

5. According to whether the compensation organization rotates with the shaft, it is divided into rotary and stop mechanical seals

(1) Rotary type: The compensation ring rotates with the shaft.

(2) Stop type: The compensation ring does not rotate with the shaft.

The usual mechanical seals are often of rotary type due to the simple structure of the compensation structure, shaft, and small radial dimension. However, under high-speed conditions, the centrifugal force generated by the compensation ring and other rolling parts has a great influence, and the dynamic balance requirement is high, so it is more appropriate to use the stop type.

Ⅱ. The mechanical seal type consists of 4 basic units based on its structural characteristics

1. Buffer compensation unit

The buffer compensation structure composed of the spring as the main component is an important condition for maintaining the normal operation of the mechanical seal.

2. Sealing unit

It is the sealing end face composed of the moving ring and the static ring, which is the core of the mekanikal seal.

3. Auxiliary sealing unit

It is composed of moving ring sealing ring, static ring sealing ring and other components. It is an auxiliary sealing structure to solve the possible leakage of parts other than the sealing end face, an indispensable component of mechanical seals. Mechanical seal is a promising form of sealing in fluid sealing technology, which can meet the requirements of most production process conditions.

4. Transmission unit

It is a transmission mechanism composed of shaft sleeves, keys or fixed pins. It is a reliable guarantee for completing the rotation of the moving ring with the shaft, and is also a prerequisite for completing the dynamic seal.