Views: 3488 Author: Site Editor Publish Time: 2020-04-06 Origin: Site
Mechanical seals are shaft seals for rotating machinery, such as centrifugal pumps, centrifuges, reactors, and compressors. Because the transmission shaft runs through the inside and outside of the device, there is a circumferential gap between the shaft and the device. The medium in the device leaks out through this gap. If the pressure inside the device is lower than the atmospheric pressure, air will leak into the device, so there must be a shaft seal to stop leaking. There are many types of shaft seals. Because mechanical seals have the advantages of low leakage and long life, mechanical seals are the most important shaft seal method in these devices in the world.
The mechanical seal is mainly composed of a moving ring, a static ring, a cooling device and a compression spring.
The auxiliary seals for mechanical seals are mainly sealing rings, including O-shaped, X-shaped, U-shaped, wedge-shaped, rectangular flexible graphite, and PTFE-coated rubber O-rings.
The elastic compensation mechanism of the mechanical seal includes springs, push rings, spring seats and various screws.
The mechanical seal is divided into single end face and double end face. It can be divided into balanced type and unbalanced type, and it can also be divided into arbitrary rotation direction and fixed rotation direction.
A mechanical seal, also called an end face seal, refers to a device for preventing fluid leakage formed by at least one pair of end faces relatively sliding which is perpendicular to the rotation axis under the action of fluid pressure and the elastic force of the compensation mechanism and the cooperation of the auxiliary seal. The structure of the mechanical seal includes a stationary ring, a rotating ring, an elastic element spring seat, a set screw, a rotating ring auxiliary sealing ring and a stationary ring auxiliary sealing ring. The anti-rotation pin is fixed on the gland to prevent the stationary ring from rotating. Rotating and stationary rings are often called compensation or non-compensation rings depending on whether they have axial compensation capabilities.
In the past, the shaft seal box containing mechanical seals was a stuffing box designed for soft packing seals. It is not suitable for holding mechanical seals. Not only is the size too small, the gap is too narrow, but also the simple cylindrical shape is not suitable. Foreign countries have established standards for increasing the size of mechanically sealed shaft-sealed boxes. In addition, the United States_Duramitel Corporation and the British Fluid Mechanics Research Group are both researching reasonable mechanical seal shaft seal boxes. The shape should not only be conducive to fluid flow and heat dissipation, but also to remove solid particles.
In the past, attention was only paid to eliminating visible fluid leakage, and pay little attention to the control of invisible volatiles, which caused environmental pollution and was dangerous to the device and the person. Some foreign associations have formulated guidelines for controlling volatile emissions from rotating machinery, compressors, and screw systems with mechanical seals in SP-30 (1994), SP-32 (1990), and SP-33 (1991).
The mechanical seal auxiliary system needs to include cooling, heating, flushing and other systems, the pump cycle needs to be optimized, and problems such as condition monitoring systems are being researched and solved.
In the past, liquids were used to block liquids or gas. In order to simplify the bulky liquid blocking system, gas was used to block liquid or gas. In the block sealing system, a spiral groove gas seal can be used to block the gas, and a floating sleeve gas seal can be used to block the gas and liquid.
Hopefully this passage can help you when you get confused about mechanical seal.