Luzhongbao 700x800x120 Square Outer Frame with Circular Inner Core & Anti-Falling Net

The Luzhongbao 700×800×120 square outer frame with circular inner core manhole cover, equipped with an anti-falling net, is a heavy-duty protective facility specifically designed for modern urban areas with high safety standards. This product is precision-cast using QT500-7 grade high-strength ductile iron, strictly adhering to the GB/T23858 national standard and the EN124 international standard. Its unique square outer frame with circular inner core structure (external 700mm × 800mm rectangular frame, internally adapting to a standard circular manhole opening) meets the coverage requirements of large manholes while providing a larger load dispersion area. The 120mm ultra-deep frame, combined with a bottom extended flange design, directly transmits wheel loads to the road structural layers, fundamentally addressing the industry-wide issue of asphalt settlement around the manhole from a structural principle perspective. The built-in high-strength nylon anti-falling net (load-bearing capacity ≥ 1000 kg) provides double protection, preventing accidental human falls, making it particularly suitable for places with extremely high public safety requirements such as school campuses, plazas, and sidewalks.

Compared to ordinary products, Luzhongbao has established its industry-leading position through multiple advantages: firstly, advantages in materials science, using QT500-7 ductile iron with tensile strength ≥ 500 MPa and yield strength ≥ 320 MPa, mechanical properties far exceeding ordinary cast iron covers; secondly, advantages in structural design, the innovative square outer frame with circular inner core structure and deepened frame design achieve scientific load dispersion and vertical transmission; thirdly, advantages in process precision, the cover-frame fit gap is ≤ 1 mm, far exceeding the industry standard of ≤ 2 mm, ensuring stable and noiseless operation after installation; fourthly, advantages in comprehensive solutions, providing a complete protection system from fall prevention, and theft prevention to settlement prevention. These advantages enable Luzhongbao not only to meet the D400 grade (400 kN) load-bearing requirement but also to adapt to China's complex and diverse urban environments, providing long-lasting and reliable protection for municipal infrastructure.

The cast iron square outer frame with circular inner core cover adopts a unique design that combines the advantages of a square outer frame and a circular cover, providing a more stable and robust structure. It is widely used in various fields such as municipal roads, commercial areas, and industrial parks. This design enables the cover to effectively withstand pressure from all directions while simplifying installation and maintenance work, enhancing the product's usability and durability.

Advantages of the Square Outer Frame with Circular Inner Core Design:

Improved Installation Stability: The square outer design facilitates the positioning of the cover relative to the frame, avoiding potential sliding or misplacement common with circular covers, ensuring cover stability.

Enhanced Load-Bearing Capacity: The circular inner cover design effectively disperses loads from different directions, allowing the cover to remain stable under high-intensity loads, capable of withstanding D400 grade high pressure, meeting the needs of heavy-duty areas.

Easy Opening and Maintenance: The square outer frame with circular inner core design not only simplifies the installation process but also makes the cover easier to open, reducing the difficulty of maintenance and inspection.

Reduced Unnecessary Noise: Due to the excellent fit of the square outer frame with circular inner core design, friction between the cover and frame is effectively reduced, avoiding phenomena like bouncing and displacement, thus lowering noise pollution.

The cast iron square outer frame with circular inner core cover surface is treated with paint, providing excellent rust resistance, able to resist erosion from damp and corrosive environments, extending its service life.

Detailed Explanation of Core Product Advantages

1. Multiple Protections and Intrinsic Safety

Fall Prevention Guarantee: A high-strength anti-falling net is standard below the cover, using a combination of corrosion-resistant nylon rope and stainless steel hooks. The mesh is uniform and dense, with a static load-bearing capacity exceeding 1000 kg. Even if the cover opens unexpectedly, it effectively intercepts falls, providing crucial secondary safety protection for pedestrians.

Anti-Theft and Stability: The design incorporates concealed hinges paired with anti-theft locks, with no exposed fasteners, effectively preventing illegal opening. The millimeter-level precise engagement between the cover plate and the frame eliminates bouncing, slipping, and abnormal noises during vehicle traffic, fundamentally eliminating safety hazards caused by cover displacement.

Anti-Settlement Performance: The core of settlement prevention lies in the frame's 120mm deepened design and the bottom ultra-wide flange (width ≥ 200mm). This structure allows wheel pressure to be vertically dispersed through the frame's sidewalls to the road base, bypassing the easily compacted backfill soil area, thus ensuring the cover and road surface remain level long-term, achieving the "zero settlement" goal.

2. Exceptional Load-Bearing and Durability

Superior Load-Bearing Foundation: Thanks to the QT500-7 ductile iron material and the internal radial reinforcement rib structure, this cover possesses extremely high compressive, impact, and fatigue resistance, easily passing D400 grade (400 kN) certification, and can confidently handle harsh environments with frequent heavy vehicle traffic.

Long-Lasting Corrosion and Weather Resistance: The product surface uses a heavy-duty anti-corrosion composite coating (typically hot-dip galvanizing + epoxy asphalt spray), with a zinc layer thickness ≥ 80μm, and salt spray test resistance exceeding 2000 hours. It effectively resists erosion from urban acid rain, de-icing agents, and underground damp environments. The design service life can exceed 30 years, far surpassing the lifecycle of ordinary products on the market.

3. Precision Manufacturing and Intelligent Operation & Maintenance

Precision Manufacturing Process: Relying on the technology and quality control standards used for supplying core components to mega-projects like the Hong Kong-Zhuhai-Macao Bridge and the Shenzhen-Zhongshan Link, Luzhongbao ensures the cover's dimensional tolerances and assembly accuracy reach the industry's top level, achieving perfect adaptation and a smooth, quiet user experience.

Smart Function Integration: The product can be optionally equipped with RFID electronic tags or NFC chips, facilitating digital asset management, rapid identification, and traceability for municipal departments. This function greatly improves the efficiency of daily inspection, maintenance, and inventory management, aligning with the development trend of smart cities.

The Luzhongbao 700×800×120 manhole cover with an anti-falling net, through its comprehensive advantages in materials, structure, craftsmanship, and intelligent operation and maintenance, sets a new benchmark for urban public safety. It is not merely a functional component but a reliable protective solution, a key investment in enhancing the resilience of urban infrastructure and the sense of security for residents.