Metal Bellow Mechanical Seals are high-performance sealing devices that are widely used in pump systems in the chemical, petroleum, and natural gas industries. Its working principle is based on the elasticity and flexibility of the bellows, which can work under high temperature and high pressure conditions and has strong adaptability to handle the offset and vibration between rotating shafts.
Metal Bellow Mechanical Seals mainly include corrugated metal tubes, usually made of stainless steel. One end of the bellows is connected to the rotating shaft or sealing end of the pump, while the other end is connected to the pump casing. When the feedwater pump is started, the rotating shaft begins to rotate and the bellows rotates with it. Due to the elasticity of the bellows, it can stretch and contract to adapt to the changes in the mechanical seal interface.
Elastic Compensation: The elasticity of the bellows enables it to adapt to the rotation and vibration of the shaft, thereby maintaining close contact between the sealing surfaces to prevent leakage.
Pressure Balance: Both ends of the bellows are usually in contact with the sealing surface to prevent liquid leakage. The elasticity of the bellows forms a tiny gap at the junction (sealing interface) between the sealing end faces. When the pressurized medium passes through this gap, an extremely thin liquid film is formed, which generates resistance and prevents the medium from leaking. At the same time, the liquid film lubricates the end face.
Automatic compensation: When the sealing end face is worn, the dynamic ring and the dynamic ring seal ring move slightly along the axial direction under the push of the spring to achieve a certain compensation capacity, so it is called a compensation ring. Through different structural designs, the compensation ring can be borne by the dynamic ring or the static ring.
High precision: The welded bellows acts as a spring, and it is a combination of many springs, which solves the problem of ordinary springs deforming due to centrifugal force, adapts to high rotation, and makes the sealing surface evenly pressurized, which is conducive to preventing leakage.
Vibration resistance and flexibility: The bellows are highly flexible and have a very good vibration absorption effect, so they have a strong adaptability to radial runout, axial clearance, vibration and swing, and can effectively prevent leakage.
Simple structure: Metal Bellow Mechanical Seals are not like other ordinary mechanical seals that are composed of many parts. They have the characteristics of integrated assembly, simple structure and easy assembly.
Installation deviation: Pay great attention to avoid installation deviations during installation, such as the deflection of the gland end face and the matching clearance between the gland and the outer diameter of the shaft or sleeve.
Spring compression: The spring compression should be carried out according to regulations. It is not allowed to be too large or too small. The error is required to be 2.00 mm. Too large will increase the end face pressure ratio and accelerate the end face wear. Too small will cause insufficient pressure ratio and fail to play a sealing role3.
Moving ring installation: After the moving ring is installed, it should be able to bounce back automatically after pressing the moving ring against the spring.
