Valves frequently encounter various operational issues, the most common and severe being packing leakage. This problem not only leads to significant resource waste but also forces frequent plant shutdowns, resulting in high costs associated with energy loss. Furthermore, leaks involving sensitive materials can be corrosive or pose risks of fire, explosion, and equipment damage, leading to massive economic losses and safety hazards.
Addressing these challenges with conventional packing-sealed valves requires constant maintenance access, which complicates the maintenance process. Personnel must regularly inspect and replace packing to ensure proper valve operation. However, this approach is labor-intensive and time-consuming, and improper handling can even trigger new issues. Additionally, frequent maintenance drives up operational costs and reduces production efficiency.
The bellows design offers an effective solution to these problems. As a modern sealing component, the bellows offers excellent sealing performance and a long service life. It operates reliably under high-temperature conditions and withstands over 10,000 operating cycles without failure, significantly enhancing valve reliability.
What Design Features Ensure the Sealing Integrity of Bellows-Sealed Globe Valves?
Metal Bellows Barrier Design: A dual-layer, hydraulically formed bellows made of 316L/316Ti stainless steel is used. Its lower end is precision-welded to the valve stem, and its upper end is welded to the interior of the bonnet, creating a complete metal isolation barrier that prevents the medium from coming into contact with the upper stem and packing area.
Dual Sealing (Bellows + Packing): In addition to the primary bellows seal, a secondary sealing layer—comprising flexible graphite braided with stainless steel wire—is installed on the upper stem. Even if the bellows’ performance degrades due to long-term fatigue, the packing acts as a second line of defense to prevent leakage, providing a safety redundancy for the seal.
Precision Design of Internal Sealing Pairs: The sealing pair utilizes a combination of conical and flat mating surfaces. This allows for slight automatic compensation during closure; even with minor wear on the sealing surfaces, a tight fit is maintained, ensuring stable, long-term sealing performance without adhesive wear.
Design of Auxiliary Structures to Prevent Failure:
- A long, self-lubricating guide bearing is installed inside the bonnet to constrain the stem’s radial displacement throughout its travel. This ensures high-precision coaxial alignment between the stem and the bellows, preventing lateral stem vibration caused by high-pressure fluid impingement and protecting the bellows from fatigue fracture due to lateral forces or twisting.
- A non-rotating rising stem design is employed; the stem moves only in a straight axial line during opening and closing. Since no circumferential torque is generated, the risk of the bellows being twisted or torn is completely eliminated.
The advantages of bellows extend beyond their excellent sealing performance and long service life to include remarkable adaptability. They can be customized to suit specific operating conditions and media requirements, meeting a wide range of complex application needs. Whether dealing with high temperatures, high pressures, or corrosive media, bellows provide a stable seal, ensuring the valve operates reliably. Furthermore, the installation and replacement of bellows are relatively simple and convenient, significantly reducing maintenance time and boosting operational efficiency.
In summary, the bellows design offers an effective solution for valve sealing challenges, significantly enhancing reliability and safety while reducing maintenance costs and environmental impact. For enterprises, adopting bellows-sealed valves not only improves production efficiency and product quality but also lowers operating costs and safety risks.
As a professional valve manufacturer, AIV offers high-quality bellows globe valves. Please feel free to contact us if you would like to learn more about valves.