A welded metallic bellows replaces the conventional packing stack, pushing stem leakage toward zero in API 602 high-pressure isolation. [S1]
Specifying engineers handling toxic, radioactive, or cryogenic media gain a stem seal that does not depend on packing compression, removing the dominant leak path in rising-stem valves. The trade-off is a fatigue-limited bellows element that must be leak-tested and documented to a defined sensitivity, and the API 602 pressure class and material limits set the envelope in which that design is qualified. [S1]
What the product is and how it seals
A bellow seal valve substitutes a metallic bellows assembly, welded to both the bonnet and the stem, for the conventional packing stack around the stem. The body of the article describes this as a hermetic seal that eliminates stem leakage to essentially zero. [S1]
Operation is mechanical: when the stem moves to open or close, the bellows expands or contracts with it, so no gap opens between stem and bonnet. The article presents the construction as straightforward, and groups the resulting capability under zero-leakage design, high durability, corrosion resistance, and suitability for hazardous or toxic media. [S1]
Numbers, names, and standards given
The article references API 602 as the governing standard for a bellow seal gate valve design and lists pressure class ratings from 150 to 2500, calling out approximately 300 PSI at class 150 and approximately 5000 PSI at class 2500. [S1]
Body and bonnet materials are split by class: ductile iron is listed for class 150 to 900, and carbon steel forgings for class 1500 to 2500. Stem material is identified as stainless steel, typically 410 or 416, and bellows material as austenitic stainless steel, typically 304 or 316L. [S1]
Leak testing is specified as helium leak testing with a sensitivity of ≤ 1×10⁻⁶ atm-cc/sec. The article also states that the supplier, PANS Valve, manufactures bellow seal valves to ISO 9001 and provides full traceability documentation. [S1]
Implications for the product category
The design is positioned for service where packing is the weak link: chemical processing with toxic and corrosive fluids, nuclear power with radioactive media, LNG at cryogenic temperatures, pharmaceutical manufacturing requiring contamination control, and refinery and oil and gas lines at high pressure. The article contrasts bellow seal globe valves against conventional globe valves on the maintenance and leak path, with the conventional design dependent on packing that can wear and leak. [S1]
The published comparison table begins with leakage rate as the first dimension but is truncated in the source, so any side-by-side ranking beyond the leakage, maintenance, and safety arguments described in the prose should be checked at the source URL. The article also references a separate API 602 standard text establishing design, manufacturing, and testing requirements; specifying engineers should treat the pressure class, material, and leak rate values as supplier-stated summaries pending confirmation against the current API 602 edition. [S1]
How to verify the primary source
Open the source URL to confirm the API 602 pressure class table, the listed material grades for body, bonnet, stem, and bellows, and the helium leak rate limit of ≤ 1×10⁻⁶ atm-cc/sec against the current API 602 standard. [S1]
Cross-check the application list, which is given as chemical processing, nuclear power, LNG, pharmaceutical, and refinery and oil and gas, against any project-specific code or regulatory requirement before substituting a bellow seal design for a packed valve. [S1]
Primary notice: Industry news.
Product encyclopedia: Bellows Seal.