Bellow Seal

Bellows sealed valves are globe stop valves used for isolation or limited throttling in lines where stem leakage must be controlled by a metallic barrier rather than relying only on packing. The bellows isolates the stem from the process fluid, while the graphite packing serves as a secondary seal. They are commonly selected for steam, condensate, hot water, thermal oil, process water, vacuum service, ammonia, and various process gases and liquids.

This category includes ARI FABA Plus and FABA Supra designs in DIN and ANSI versions, in both industrial and chemical service configurations, as well as valves from Valvosider, Comeval, Neway, and Fluitek for general industry, power generation, chemical processing, oil and gas, and selected nuclear duty applications. Available body patterns include straight-through, 90° angle pattern, and Y-pattern. Y-pattern versions are used where lower pressure drop is required compared with conventional globe geometry, while angle pattern valves are applied where the piping layout itself requires a change in flow direction.

Technical selection is based on DN/NPS, PN or ASME Class, operating temperature, service pressure, flow direction, end connection, and compatibility of body and trim materials with the process medium. Available configurations include flanged, butt weld, socket weld, and NPT ends, with materials such as cast iron, carbon steel, low-temperature carbon steel, stainless steel, alloy steel, and nickel alloys. Evaluation should consider the inherent pressure loss of globe-type flow paths, required seat tightness class, bellows cycle life, and accessibility for maintenance of the bonnet, packing, and actuator or handwheel assembly.