III. Features Description

• Bellow Seal Zero Leakage: The 304/316 stainless steel bellow is welded between the stem and bonnet, forming a permanent seal that eliminates stem leakage—unlike traditional packing seals that degrade over time. This is critical for WOG media, where even minor leakage risks safety or environmental hazards.
• Dual Sealing Backup: Bellow (primary) and packing (secondary) create a redundant sealing system. If the bellow is damaged, the packing prevents immediate leakage, providing time for maintenance and avoiding unplanned shutdowns.
• Outer Screw Stem Design: The stem screw is external, avoiding contact with media and reducing wear from corrosion or abrasion. This extends stem life and ensures smooth operation, even in dusty industrial environments.
• DIN Standard Compatibility: Flange dimensions and face-to-face lengths comply with DIN standards, fitting seamlessly into European industrial pipelines. This avoids adaptation issues in cross-border projects, simplifying installation.
• Material Versatility: GS-C25/WCB for general industrial use, 1.4408 stainless steel for corrosive media—allowing customization to match specific media properties (e.g., humid air, light oils, or water).

IV. Manufacturing Processes

• Material Validation: GS-C25/WCB castings undergo ultrasonic testing to detect internal defects; stainless steel components (bellow, stem) are tested for chemical composition to ensure corrosion resistance.
• Bellow Forming: 304/316 sheets are rolled into tubes, then hydraulically formed into corrugated bellows. TIG welding connects the bellow to the stem and bonnet, with helium leak testing (≤1×10⁻⁹ Pa·m³/s) to verify hermetic sealing.
• Precision Machining: Body flanges and flow channels are CNC-machined to DIN EN 1092-1 dimensions, with bolt holes aligned to ±0.5mm for easy installation. Disc and seat surfaces are ground to Ra ≤1.6μm for tight contact.
• Assembly & Testing:
  • Hydrostatic Test: Body tested at 1.5×rated pressure (e.g., 9.6MPa for PN64) for 30 minutes; seat tested at 1.1×rated pressure with water to confirm no leakage.
  • Operation Test: 100+ open/close cycles to ensure smooth stem movement and consistent sealing, with focus on outer screw stem reliability.
  • Coating Application: Epoxy painting (custom colors optional) protects the exterior from rust, extending service life in outdoor or humid environments.