Mechanical Seal for Pressure Screen and Pump

Product Description

Mechanical seal refers to a device that prevents fluid leakage by at least one pair of end faces perpendicular to the rotational axis, under the action of fluid pressure and compensation mechanism elasticity (or magnetic force), as well as the coordination of auxiliary seals, to maintain a close fit and relative sliding of the end faces. 

Mechanical seal is a shaft sealing device used in rotating fluid machinery. For example, equipment such as centrifugal pumps, centrifuges, reactors, and compressors. Due to the transmission shaft penetrating inside and outside the equipment, there is a circumferential gap between the shaft and the equipment, through which the medium in the equipment leaks outward. If the pressure inside the equipment is lower than atmospheric pressure, air leaks into the equipment. Therefore, there must be a shaft sealing device to prevent leakage.

Component

Main components:

Dynamic ring, static ring, cooling device, and compression spring (depending on the specific equipment).

Auxiliary seal:

Sealing rings (including O-ring, X-shaped, U-shaped, wedge-shaped, rectangular flexible graphite, PTFE coated rubber O-ring, etc.).

Elastic compensation mechanism:

Springs, push rings.

Spring seat and key or various screws.

Working Principle

Mechanical seal is a shaft sealing device that achieves leakage resistance by maintaining a pair or several pairs of opposite sliding faces perpendicular to the shaft under the action of fluid pressure and the elastic (or magnetic) force of the compensation mechanism, and assisting in sealing.

The commonly used mechanical seal structure consists of static ring (static ring), rotating ring (dynamic ring), elastic element spring seat, push ring, set screw, rotating ring auxiliary seal ring, and static ring auxiliary seal ring. The anti rotation pin is fixed on the gland to prevent the static ring from rotating.

Rotating and stationary rings are often referred to as compensating or non compensating rings based on whether they have axial compensation capability.

Advantages

1. Advantages

(1) The structure is reliable, and the leakage amount can be limited to very little. As long as the surface roughness and flatness of the main sealing surface can meet the requirements, and as long as the material has good wear resistance, the mechanical seal can achieve very little leakage.

(2) Long lifespan. In mechanical seals, the main wear part is the sealing friction pair end face, as the wear amount of the sealing end face is not significant under normal working conditions.

(3) No adjustment is required during operation. Due to the mechanical seal relying on spring force and fluid pressure to make the friction pair stick together, it automatically maintains contact during operation, and after assembly, there is no need to adjust and compress it like ordinary soft fillers.

(4) It has vibration resistance. At a speed of 3000r/min, the maximum amplitude should not exceed 0.05mm and the PV value should be continuously increased.

(5) Low power loss. The packing seal works by compressing the packing onto the shaft or shaft sleeve. The packing seal directly rubs against the shaft, and the tighter the packing is pressed, the greater the friction force and power consumption. The friction of mechanical seals is in a semi liquid friction state, with a very small friction coefficient. The power loss of mechanical seals is 10-50% of that of packing seals.

(6) The bellows sealing shaft or shaft sleeve is not subject to wear and is not sensitive to the vibration of the rotating shaft and the deviation of the shaft from the shell.

(7) Widely applicable. When the medium is flammable, explosive, toxic, or harmful, using mechanical seals can ensure sealing. It is also suitable for sealing equipment with various rotational speeds such as high temperature, low temperature, high pressure, vacuum, and corrosive media.