Atlas Copco Common Types and Structural Characteristics
Mechanical Seal
One of the most widely used types of shaft seals, it consists of a moving ring, a stationary ring, a spring, and sealing rings, etc. The moving ring rotates with the shaft, while the stationary ring is fixed on the housing. The pre-tightening force of the spring causes the end faces of the two rings to be closely adhered, forming a sealing surface. Its advantages are good sealing performance, long service life, high adaptability to rotational speed, suitability for medium and high pressure conditions, but the structure is relatively complex and high installation accuracy is required.
Frame Oil Seal
It is composed of a rubber sealing ring and a metal frame. The seal is achieved by the close contact between the rubber lip and the shaft surface. The structure is simple, the cost is low, and the installation is convenient. However, the sealing performance is greatly affected by rotational speed and pressure. It is usually used for auxiliary parts in low-pressure and low-speed situations or as an auxiliary seal for mechanical seals.
Maze Seal
It utilizes the tortuous gaps between the shaft and the sealing element (maze structure) to generate throttling effects, preventing lubricating oil from leaking. This seal has no contact wear and is suitable for high rotational speed scenarios. However, the sealing effect is relatively weak and usually requires other sealing forms to be used in combination (such as forming a combined seal with an oil seal).
Packing Seal
It is formed by pressing oil-coated graphite or asbestos onto the shaft sleeve. The structure is simple and the cost is low, but the friction resistance is high and the shaft surface is prone to wear. Currently, it is rarely used in screw compressors and is mainly used in some old models.
Main Failure Causes
Wear and Aging: Long-term friction on the moving seal surface leads to wear, or the rubber part ages and hardens due to high temperature and oil erosion, losing elasticity.
Improper Installation: The sealing element is installed crooked, too tight or too loose, or the shaft surface has scratches or impurities, damaging the seal surface adhesion.
Lubricating Oil Issues: Oil contamination, inappropriate viscosity, or insufficient oil quantity lead to poor lubrication of the seal surface, accelerating wear.
Abnormal Operating Conditions: Excessive unit pressure, abnormal rotational speed, or excessive vibration exceed the design tolerance of the sealing element.
