HOW DOES THE PUMP MECHANICAL SEAL WORK?

In the industrial field, people will use a variety of seals to prevent pipeline leakage. Common seals include gland packing, spring seal, elastic bellows seal, pump seal and mechanical seal. The following content mainly introduces how the pump mechanical seal works.

Mechanical seal is a kind of shaft seal device of rotating machinery. Such as centrifugal pumps, centrifuges, reactors and compressors and other equipment. Since the transmission shaft runs through the inside and outside of the equipment, there is a circumferential gap between the shaft and the equipment, through which the medium in the equipment leaks out. If the pressure in the equipment is lower than atmospheric pressure, the air leaks into the equipment, so there must be a shaft sealing device to prevent the leakage.

In the process of preventing leakage of liquid or gas flow, pump seal is essential. The seal has two sides, one is stationary and the other is rotating. The seal faces are so flat that no gas or liquid can flow through them. It makes the shaft rotate freely. The duration of the seal depends on the sealing material used, in addition to the purpose of the seal. It is recommended to use double mechanical seal when the equipment requires high sealing effect.

Basic Components of Pump Seal

The basic components of pump seal include rotating the shaft, stationary pump, mixer and seal-chamber housing.  Mechanical Seal are rotating-face seals or end-face seals. In some designs, hybrid of lip-type seal or circumferential seals are used. Regardless of the type of seal you use, the following components are standard on all models.

1. Rotating primary sealing element: The rotating primary seal element is driven by the shaft to seal the primary stationary sealing element. In some designs, it is fixed to the shaft.

2. Stationary primary sealing element: The element is fixed to the mixer, the fixed housing of the pump or other components. The rotating shaft passes through it and is sealed with the rotating primary sealing element.

3. Secondary seals (static or dynamic) : This seal acts between the equipment shaft and the housing and the mechanical seal components. In addition, the closing force that biases the primary sealing element, which is in contact. It initiates sealing.

The Sealing Points

In general, there are four sealing points in the pump seal. The primary seal between the stationary face and the rotating face.

The stationary seal between the stationary member and the gasket (stuffing box face).

The secondary seal between the rotating member and the shaft sleeve (or shaft) may be wedge, V-ring, O-ring or other sealing ring.

The seal between the stuffing box and gland plate can be O-ring or washer, depending on the application.

Among the above four types of seals, the most important sealing point is the primary sealing point between the stationary surface and the rotating surface.

The two faces are pressed against each other by spring force. The mating surfaces are precisely machined to make them flat. The measure of their flatness is a light band, which is an optical method.

Minimize the flatness of the surface so that leakage is almost negligible. The initial face pressure is provided by spring compression.