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It is welded to the stem and the valve body, creating a seamless barrier that prevents leaks, even in high-pressure or corrosive environments. Since these valves do not rely on packing material, they require less frequent maintenance and repair, allowing for more time to make products. This ultimately has a positive impact on uptime and operational costs.
One disadvantage with traditional packed valves is their tendency to loosen up in applications with a lot of thermal cycling. Opening and closing the valve causes rapid wear on the packing and leads to leakage of hot transfer fluids or steam. In contrast, bellows sealed valves do not require adjustments, they are durable, can withstand extreme, corrosive environments and provide a longer service life. Installing bellows sealed valves in the hottest section of the thermal loop eliminates the chance that a leak will cause a serious safety hazard.
Determining Bellows Sealed Valves
There are two ways to manufacture bellows: hydroforming or edge welding. Hydroforming involves pressurizing a metal tube into metal folds, while edge welding entails a series of washer- like plates to form the accordion shape. Both methods form a bellows seal that completes the same task.
However, hydroformed bellows are typically larger and take up more space than welded bellows. There is a common misconception that hydroformed bellows are stronger and will last longer since they incorporate fewer welds. As long as edge-welded bellows are designed and fabricated
correctly, and qualified to the MSS SP- 117 standard, the service life should be the same.
When specifying a bellows sealed valve, it is imperative to consider media / corrosion resistance, temperature rating, pressure rating, and cycle life. Standards such as ISO 15848-1, ISO 15848-2, API 622, API 624, and API 641 should be consulted during the selection process. These specifications ensure bellows sealed valves are tested rigorously for performance under challenging conditions, which significantly reduces the likelihood of leaks.
There are low emissions non-bellows valves that meet regulatory standards and minimize fugitive emissions, but they depend on correct installation, may require adjustment, may have a shorter lifespan, and do not eliminate leaks. Therefore, in a critical application requiring absolute sealing, a bellows sealed valve with zero emissions is ideal.
Unlike conventional valves that rely on gland packing to seal the stem and bonnet, bellows sealed valves use welded connections. Seen here are Dixon’ s F8-Series; J-Series; G8-Series.
Bellows sealed valves are advantageous for reducing fugitive emissions across many applications. In refineries processing hydrocarbons
24 Valve World Americas | October 2025 | www. valve-world-americas. com