The Difference Between Metal Bellows Mechanical Seals and Ordinary Mechanical Seals

Metal bellows are used in mechanical seals for high temperature, high pressure, and low temperature media. They can serve as both auxiliary seals and elastic elements. Welded metal bellows mechanical seals have good floating and random compensation capabilities, allowing them to compensate for leaks caused by wear, axial movement, and vibration of the sealing ring. The welded metal bellows themselves function as both an elastic element and a sealing component, eliminating the need for an auxiliary sealing ring in the middle of the metal bellows mechanical seal, which reduces a potential leak point and also decreases the friction resistance of the compensation mechanism.

Welded metal bellows are formed by tightly welding the inner and outer diameters of each wave sheet in an alternating pattern, so there is no need to consider the direction of rotation when used either statically or rotationally. Welded metal bellows can be manufactured from materials such as precipitation-hardening stainless steel, high-temperature nickel-based materials, and chromium-nickel corrosion-resistant materials. Therefore, welded metal bellows are suitable for a wide range of temperatures (-11―426) and various acidic, alkaline, and saline media. By selecting different wave sheet thicknesses and layers, they can withstand pressures up to about 7MPa in pumps. The design of welded metal bellows mechanical seals is generally balanced, so the pressure impact on the end face specific pressure is minimal. Metal bellows mechanical seals are not only suitable for non-hydrocarbon media but also for flash hydrocarbon media. Compared to ordinary mechanical seals, their service life is greatly improved, resulting in a higher performance-to-price ratio.

Features of Metal Bellows Mechanical Seals

The bellows serve as a sealing element that integrates an elastic element, auxiliary seal, and torque transmission mechanism (ordinary seals do not have this capability). The torque is uniquely provided by the bellows mechanical seal. The specific pressure on the end face is uniform, and it has the characteristics of high-temperature resistance and good tracking performance. The moving ring does not have an auxiliary sealing ring, which reduces a potential leak point and also reduces the friction resistance of the moving ring.

Common bellows include pressed and welded types. Pressed bellows are made by elongating and forming thin-walled tubes on a press or using a hydraulic die; welded bellows from leading mechanical seals supplier are made by welding the inner and outer circles of thin film sheets (commonly used).

Advantages of Metal Bellows Mechanical Seals

High precision: The welded bellows act as a spring and are a combination of many springs, solving the problem of deformation due to centrifugal force in ordinary springs. They adapt to high-speed rotation and ensure uniform pressure on the sealing surface, helping to prevent leaks.

Vibration resistance and flexibility: Bellows have high flexibility and excellent vibration absorption, making them highly adaptable to radial runout, axial gaps, vibration, and oscillation, effectively preventing leaks.

Simple structure: Unlike other ordinary mechanical seals that require many parts, they feature integrated assembly, simple construction, and easy assembly.

Adaptable to various temperature conditions: Welded bellows have a low coefficient of thermal expansion and can be used in both low and high temperatures. Without O-rings, they are free from temperature constraints, allowing for more flexible design.

Suitable for high-pressure conditions: Since the bellows themselves can act as a balance, the sealing area can be designed to offset fluid pressure, reducing friction on the sealing surface, thereby decreasing heat generation and wear, making them suitable for high-pressure conditions.

No shaft sleeve, effectively protecting the pump: Welded metal bellows mechanical seals do not have O-ring mechanical seal and do not require a shaft sleeve, preventing wear on the shaft or shaft sleeve caused by O-ring abrasion, thereby protecting the pump.

Suitable for corrosive fluids: By using highly corrosion-resistant materials such as Hastelloy C276 to manufacture the welded bellows, they also avoid the corrosion issues associated with springs and O-rings, effectively achieving sealing.

No hanging leak: In ordinary push-ring mechanical seals, the leaked microfluid will solidify and deposit when it meets air, preventing the O-ring from advancing, weakening or eliminating the sealing force on the end face, leading to leaks. In contrast, Sealcon welded bellows mechanical seals do not have O-rings, so even if solidification occurs, the impact is minimal, allowing for stable rotation and a longer service life.

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