China Bolted Bonnet Gate Valve Factory & Factories

A Bolted Bonnet employs external bolting to clamp the bonnet and body flange against a flexible gasket, maintaining seal integrity through mechanical torque regardless of internal pressure. It is the premier choice for Class 150 through Class 600 applications. In contrast, Pressure Seal Bonnets use internal system pressure to drive the sealing wedge tighter against an internal ring, which becomes advantageous in ultra-high-pressure service (Class 900 and Class 1500+). However, BB configurations offer vastly superior maintenance accessibility in municipal, industrial steam, and refining systems.

Stem binding occurs when pipeline temperature spikes cause metal gate components to expand faster than the body seat ring, jamming the valve shut. ZFA utilizes precision-cast Flexible Wedges with a machined cut relief groove along the central hub. This geometry allows the wedge discs to flex independently under severe temperature gradients (up to 425°C in WCB, 550°C in alloy steels), ensuring low breakaway torque even after weeks in the closed position.

For seawater or brine handling in desalination, we supply CF8M (SS316) bodies with Monel or Duplex 2205 trims. For sour gas oilfield service, valves conform strictly to NACE MR0175 / ISO 15156, utilizing heat-treated low-hardness WCB/LCC body castings and Stellite Grade 6 overlay welds on the seat rings to resist hydrogen-induced cracking (HIC) and stress corrosion cracking.

Yes. In full compliance with API 600 and API 623 standards, our OS&Y gate valves incorporate an integral machined backseat on both the bonnet interior and the stem collar. When the valve is cranked to the fully open position, the backseat forms a metal-to-metal pressure seal that isolates the packing chamber from line media, allowing plant personnel to repoint or repack glands under emergency maintenance protocols.

Standard ductile iron and carbon steel valves from DN50 to DN300 (Class 150/PN16) are maintained as semi-finished castings with delivery within 15-20 days. Custom OEM configurations (extended stems, cryogenic bonnets, bypass arrangements, specific European brand actuators, and personalized casting tags) typically deliver in 30-45 days, supported by complete 3.1 material certificates and pressure testing logs.