The Integrated Forged Steel Bellows Sealed Globe Valve is a high-end industrial valve manufactured using a forging process and integrating a bellows metal barrier. Its key function is to design the valve body to extend the overall structure, forming a dual sealing system with the metal bellows and packing to completely eliminate media leakage at the valve stem, achieving “zero leakage.”
Working Principle
Achieving “zero leakage” sounds incredibly appealing. As actual users of valves, we all know that achieving “zero leakage” is difficult. So how exactly does the integral forged steel bellows sealed globe valve achieve “zero leakage”? Let’s take a look at its working principle.
Valve Opening
When the handwheel is rotated clockwise, the valve stem rises upwards due to the threaded mechanism. The valve disc (valve core) connected to the lower end of the valve stem then moves away from the valve seat. Simultaneously, the metal bellows fitted on the valve stem is stretched, opening the internal passage of the valve and allowing the medium to flow.
Valve Closing
When the handwheel is rotated counterclockwise, the valve stem moves downwards, causing the valve disc to press against the valve seat, cutting off the flow of the medium. At this time, the metal bellows is compressed, relying on its own elasticity to ensure a tight fit between the valve disc and the valve seat, achieving a reliable seal.
Core Sealing Mechanism
Bellows Seal
This is the most crucial feature of this valve. The lower end of the metal bellows (typically double-layered 316L stainless steel) is welded to the valve stem, while the upper end forms a static seal with the valve cover/body. This creates a complete metal barrier between the valve stem and the process medium, thoroughly isolating the medium from the external environment and achieving zero leakage.
Double Sealing Guarantee
Above the bellows assembly, a traditional stuffing box (such as graphite packing) is usually retained. This constitutes a double sealing design. Under normal circumstances, the bellows performs the primary sealing task; even if the bellows fails in extreme cases, the stuffing box above acts as a second line of defense, preventing media leakage and greatly improving the safety and reliability of the valve.
Self-Tightening Sealing Characteristic
Many designs employ a pressure self-sealing structure, meaning that the higher the medium pressure, the more it pushes the seal towards the valve seat, creating a “the greater the pressure, the tighter the seal” effect, ensuring reliable sealing even under high-pressure conditions.
Differences between Integral and Split (Welded) Forged Steel Bellows Gate Valves:
Length and Space Occupancy
Integral: The valve body and connecting ends (such as flanges) are forged in one piece, resulting in a compact structure. Because the welded transition section is eliminated, its structural length (face-to-face) is usually shorter, making it suitable for applications with dense pipe racks and limited installation space.
Split: The valve body and flange are forged separately and then welded together. This structure usually increases the additional weld length, resulting in a slightly larger overall size and slightly higher tolerance for installation displacement.
Structural Reliability
Integral: The weldless design eliminates potential welding defects (such as slag inclusions and cracks) and the heat-affected zone, resulting in stronger fatigue resistance under high pressure and cyclic loading.
Split: While welding reduces the cost of forging large or special sizes, the weld seam may become a weak point of stress concentration under extreme high temperature and pressure.
Typical Scenarios
Integral: Preferred for nuclear power, ultra-high pressure steam, and highly toxic media, especially in “zero-leakage” areas where leak point control is extremely strict.
Split: Commonly used for large-diameter or non-standard flange connections, reducing production costs through flexible combinations.
Structural Integrity and Fatigue Life
Integral: Due to one-time die forging, the material structure has a high degree of fibrousness and uniformity, completely eliminating the heat-affected zone caused by welds. Under conditions of frequent fluctuations in high temperature and high pressure, integral valve bodies are less prone to stress concentration, and their overall structural life is generally longer than that of split-type valves.
Split: The valve body and flange are connected by butt welding. Even after flaw detection, the weld seam remains a relatively weak point in terms of fatigue resistance under long-term high-pressure cycling.
Maintenance and Repairability
Differentiated Advantages: In the event of severe erosion, integral valves usually require complete replacement; while split-type valves, in certain designs, support the replacement of partial components. From the perspective of system service life, split-type valves offer better economy and flexibility in large-diameter applications.
In summary, both integral and split (welded) forged steel bellows sealed globe valves have their advantages. If you are looking for a suitable integral forged steel bellows sealed globe valve, you can take a look at Newton‘s products.
Newton’s Integrated Forged Steel Bellows Sealed Globe Valve offers the following advantages:
- VMV NEW MOLD integral forged flange, with the flange and valve body hot-forged together.
- Full bore design, meeting API 602 standards.
- Compact material, stable structure, and high strength performance ensure a leak-proof shell.
- It features a switch indicator mark for easy site management.
- Compact structure, suitable for installation in small spaces.
- Double seal design with bellows and packing enhances sealing performance.
This concludes our overview of the integrated forged steel bellows sealed globe valve. Please feel free to contact us if you have any needs.
