Eccentric Hemispherical Valve

I. Product Overview
The eccentric hemispherical valve (specifically, the double-eccentric hemispherical valve) is a high-performance, wear-resistant shut-off valve designed for demanding applications involving particulates, slurries, scaling, and high abrasion. It features a unique double-eccentric design that utilizes the offset between the valve shaft and the hemispherical plug to ensure a specific sequence during opening and closing: disengagement of sealing surfaces first, followed by rotation, and finally compression. This process eliminates sliding friction, jamming, and seat scraping.
When fully open, the hemispherical plug retracts into a side cavity of the valve body, creating a completely unobstructed flow path with minimal flow resistance and no dead zones for sediment accumulation. Upon closing, the valve performs a mechanical shearing and squeezing action capable of cutting through fibers, debris, and scale layers, thereby automatically cleaning the sealing surfaces. Available with manual, worm gear, pneumatic, or electric actuation, it is widely used in harsh environments—such as municipal sewage, mining slurries, chemical slurries, power plant ash water, and metallurgical waste—making it a superior, wear-resistant alternative to gate valves, butterfly valves, and standard ball valves.
II. Working Principle (Double-Eccentric Mechanism)
The eccentric hemispherical valve achieves zero-wear sealing through its spatial double-eccentric mechanical structure:
2. Opening process: The plug first moves axially away from the seat and sealing surface, then rotates 90° to open; the sealing surfaces experience no friction or scraping throughout the process.
2. Closing process: The plug rotates into position first, then uses eccentric torque to forcibly compress against the seat, creating a high-integrity seal; simultaneously, the shearing action cuts through entangled fibers and accumulated debris.
Unlike standard valves, this design ensures no wear during operation, no jamming due to scaling, no clogging from debris, and a seal that improves with use.
III. Structural Configurations
2. Side-entry eccentric hemispherical valve: Cost-effective with a proven design; suitable for standard sewage and slurry applications.

• Top-entry eccentric hemispherical valve: Allows for in-line maintenance without removing the pipeline; suitable for continuous operation scenarios where production shutdowns must be avoided. 2. Optional flange or welded connections: Compatible with various installation methods for pipelines, tanks, and equipment.
  IV. Key Structural Features

1. Double-eccentric, friction-free sealing: Zero sliding wear on sealing surfaces throughout the opening and closing process; completely eliminates issues common to traditional valves—such as wear-induced internal leakage and jamming—thereby extending service life several-fold.
2. Built-in shearing and self-cleaning function: Knife-edge shearing action upon closing cuts through aquatic weeds, fibers, sludge clumps, and fine particles, preventing entanglement or valve jamming.
3. Full-bore, flat-bottomed flow path with no dead zones: The valve body features a flat bottom without grooves or sediment traps, ensuring smooth media flow and minimizing accumulation; ideal for high-turbidity or solids-laden media.
4. High-strength, wear-resistant sealing pair: The hemispherical surface is hard-faced with a nickel-based alloy and hardened; the valve seat offers superior wear and corrosion resistance, withstanding erosion, abrasion, and particle impact.
5. Bi-directional pressure sealing: Capable of sealing against pressure from either direction, accommodating complex pipeline conditions involving pressure differentials or backflow.

• Low operating torque: Friction-free rotation after unseating allows for effortless opening and closing; compatible with smaller actuators, resulting in lower automation costs.

2. Jam-proof and scale-resistant: Unique unseating design ensures normal operation even after long-term service involving scale buildup, preventing jamming or failure. V. Material Specifications
3. Valve Body: Ductile iron, WCB carbon steel, 304/316 stainless steel
4. Hemispherical Valve Core: Base material + nickel-based alloy hard-facing (spray welding); wear-resistant and anti-corrosion treated
5. Valve Seat: Hard alloy, wear-resistant stainless steel (metal-to-metal hard seal)
6. Valve Stem: 2Cr13, 304, 316L high-strength stainless steel
7. Sealing Type: Metal-to-metal hard seal; soft/hard composite seal (optional)
   VI. Technical Parameters
8. Nominal Diameter: DN50–DN2000
9. Pressure Rating: PN10, PN16, PN25, PN40, PN64
10. Operating Temperature: -29°C to 425°C
11. Connection Method: Flanged, butt-weld

• Actuation: Manual worm gear, pneumatic, electric, hydraulic

2. Leakage Class: Class IV–VI (zero leakage for hard seals)
3. Protection Rating: IP65
4. Explosion-proof Rating: Ex d IIC T6 (optional for electric/pneumatic models)
5. Applicable Media: Sewage, mineral slurry, ash-laden water, desulfurization slurry, fluids containing particles, fibrous media, industrial wastewater, water containing silt/sand
   VII. Applicable Operating Conditions
   ✅ Recommended Applications
6. Municipal Water Supply/Drainage & Sewage Treatment Plants: Transport and shut-off of sludge, sewage, and wastewater containing impurities
7. Mining & Metallurgy: Pipelines for mineral slurry, tailings slurry, slag-laden water, and media containing solid particles

• Power Plants & Thermal Systems: Ash removal water, desulfurization/denitrification slurry, circulating water systems

1. Chemical & Paper Industries: Fibrous media, viscous materials, and media prone to crystallization or scaling
2. Harsh conditions involving high wear, sedimentation, entanglement, or scenarios where traditional valves easily jam or suffer internal leakage
   ❌ Inapplicable Operating Conditions

• Highly acidic, highly alkaline, or strongly corrosive media (fluorine-lined valves required)
• Extra-large particles or large, sharp, hard materials (risk of impact damage to sealing surfaces)
• Operating conditions exceeding rated temperature and pressure parameters
  VIII. Applicable Standards
• Design and Manufacturing: GB/T12224, GB/T12237
• Flange Standards: HG20592, ASME B16.5
• Pressure Testing: GB/T13927, API598
• Fire-safe and Anti-static: API607
  IX. Installation and Usage Instructions
• Before installation, clear the pipeline of welding slag, stones, and debris to prevent hard particles from damaging sealing surfaces.
• The valve can be installed horizontally or vertically; there are no strict flow direction restrictions, and it supports bi-directional use.
• For slurry and sludge applications, periodic full-stroke opening and closing is recommended to utilize the shearing function for clearing scale and sediment, thereby preventing valve jamming.
• For automated models, calibrate the travel limits; avoid over-travel compression to protect the sealing structure.
• In high-temperature applications, increase the temperature gradually to avoid structural deformation caused by thermal shock.
• Top-entry models allow for in-line maintenance without dismantling the pipeline, significantly reducing operation and maintenance costs.
  X. Summary of Product Advantages
  With four core advantages—friction-free opening/closing via a double-eccentric design, self-cleaning shearing action, a flat-bottom design that prevents sediment accumulation, and superior wear resistance—the eccentric hemispherical valve effectively resolves industry pain points associated with harsh applications (such as sewage, mineral slurry, desulfurization, and sludge handling), including valve jamming, sedimentation, wear, internal leakage, and short service life. Featuring high flow capacity, extremely low failure rates, and long maintenance-free intervals, it is the preferred high-performance, wear-resistant shut-off valve for solid-liquid two-phase, particle-laden, and scaling-prone applications.