Basic Knowledge of Metal Bellows Mechanical Seals

Metal Bellows Mechanical Seals are single-face, balanced, and can rotate in any direction. The O-rings and flexible graphite rings of the rotating ring do not provide compensation, hence the bellows move without resistance, making it suitable for high-temperature and high-viscosity media.

The material of the friction pair and auxiliary sealing material of the bellows mechanical seal should be selected according to the actual working conditions.

Metal Bellows Mechanical Seals are suitable for high-temperature and high-speed conditions, and torque transmission does not affect the bellows. There are no other elastic elements forming secondary seals, and the non-compensating ring can be assembled as needed.

Metal Bellows Mechanical Seals Application Scope

The application range of bellows mechanical seals is extensive. They can be used from low to high temperatures, from neutral to corrosive media, from low speed to high speed, and under various working conditions. This diversity can be achieved by changing the geometric shape of the bellows (such as inner and outer diameters, wave thickness, and number of waves) and the elastic modulus of the material, thereby altering the elasticity of the bellows. Depending on the corrosiveness of the medium, different bellows materials can be chosen. For example, for neutral media with low pressure and temperature (like oil and water), simple bellows seals made of rubber may be used. For corrosive media (like acids or alkalis), bellows seals made of Teflon may be selected. Under high temperatures and high speed, welded Metal Bellows Mechanical Seals can be used.

Metal Bellows Mechanical Seals Main Features

In general mechanical seals (pusher type), the spring maintains the compression and balance of the friction surfaces. Metal Bellows Mechanical Seals not only act as a spring but also have a sealing structure, thus the design does not require a rotating ring O-ring. Metal Bellows Mechanical Seals have many advantages over ordinary mechanical seals, summarized as follows:

High Precision

The metal bellows act as springs and are combinations of countless springs, solving the deformation issue of ordinary springs due to centrifugal force. They are suitable for high-speed rotation, with the sealing surface under even pressure, preventing leakage.

Vibration Resistance and Excellent Flexibility

Bellows have high flexibility, providing excellent vibration absorption, suitable for radial runout, axial clearance, vibration, and wobble situations, effectively preventing leakage.

Simple Structure

Simple construction and easy assembly.

Adaptable to Various Temperature Conditions

The thermal expansion coefficient of metal bellows is small, suitable for use in low or high temperatures. Without an O-ring, it is free from temperature limitations, allowing more flexible design.

Suitable for High Pressure

The bellows themselves act as a balance, adjusting the seal surface area to counterbalance fluid pressure, reducing friction and heat generation on the seal surface, making them suitable for high-pressure environments.

Machine Protection (No Shaft Sleeve Required)

Metal Bellows Mechanical Seals do not have O-rings, thus avoiding shaft or sleeve wear caused by O-ring abrasion, protecting the shaft and eliminating the need for a shaft sleeve.

Suitable for Corrosive Fluids

Using highly corrosion-resistant materials such as Hastelloy 276 for welded bellows prevents corrosion issues with springs and O-rings, ensuring the seal.

No Hang-Up

In ordinary pusher type mechanical seals, leaked fluid solidifies in the air, preventing the rotating ring  O-ring from advancing. This weakens or eliminates the seal face contact, leading to leakage. In contrast, Metal Bellows Mechanical Seals do not have O-rings, even solidified substances do not affect them, ensuring stable rotation and prolonged service life.

Threaded Pumping Action

The bellows themselves have a threaded pumping action, effectively handling fluids containing solid particles and aiding in flushing.