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Legendary size

Hercules™ D400* manhole covers

Designed to perform under pressure, Hercules D400* manhole covers are the ideal solution for large-scale Group 4 applications, providing a strong, cost-effective and fully compliant alternative to fabricated steel options. Built for carriageways and heavily trafficked areas, they deliver reliable load distribution, secure seating and durable skid resistance to protect both road users and underground infrastructure.

Hercules manhole cover

Large chambers are commonly covered with steel access covers. But when the chamber is located in a Group 4 trafficked environment, steel rarely provides the solution. That’s where Hercules comes in, providing a durable, ductile iron solution to clear openings up to 1.2m x 1.2m.

Manufactured from high-strength ductile iron, Hercules D400 covers combine strength with precise engineering and a robust single-piece (unwelded) frame. The result is exceptional longevity, reduced maintenance and consistent performance, ensuring every installation meets the highest standards of safety, durability and cost efficiency.

Although covers above 1000 mm clear opening are outside the scope of BS EN 124:2015, Hercules has been engineered and tested to the same D400 performance criteria.

The covers feature a small, secure inspection window, allowing simple visual checks without the need to remove the full cover. This single-person inspection capability saves time, reduces handling risks and helps to keep maintenance efficient. For larger works, a threaded lifting eye can be attached to allow for safe, mechanical lifting, supporting compliance with manual handling best practice.

The anti-flex design of the Hercules D400 range ensures exceptional rigidity across the full span, preventing seating wear and eliminating excessive noise - a common cause of premature ironwork failure. Together, these features make Hercules covers a robust, reliable and low-maintenance choice, offering exceptional whole-life performance in the most demanding environments.

Unmatched benefits for contractors and operators

  • The double triangular covers are indexed to ensure correct orientation when fitting
  • Inspection window allows for easy inspection, preventing the need to remove covers
  • A threaded lifting eye can be secured to allow for mechanical lifting - making it easier and safer to move and inspect
  • Anti-flex covers prevent seating wear, eliminating excessive noise and catastrophic failure
  • Enlarged frame corners help to dissipate load, minimising bearing pressures
  • Suits large chambers - up to 1.2m clear opening
  • UKAS-accredited third-party certification (70+PSVR tested)
  • Tested to BS EN 124 performance criteria

Square or rectangular manhole covers

Stock code Range Clear opening
(mm)
Overall frame
(mm)
Frame depth
(mm)
Options My Wrekin Downloads
DMT0D6/1212/4 Hercules 1,200 x 1,200 1,385 x 1,385 150

Key benefits of Hercules manhole covers

Engineered for heavy-duty applications

Manufactured from high-strength ductile iron, delivering D400* performance levels with high levels of skid resistance (70+ PSRV)

Large-format capability

Specifically designed for extra-large Group 4 chambers.

Cost-effective alternative to steel

Provides a more economical option than large fabricated steel covers, reducing both initial material costs and ongoing maintenance.

Whole-life performance

Long-lasting ductile iron construction delivers exceptional durability and resistance to fatigue, impact and deformation under repeated loading.

Inspection window on Hercules manhole cover
Inspection window

Smart Access, Safer Inspections

The inspection window on Hercules manhole covers allows quick, safe visual checks without removing the entire cover. This simple but effective feature supports single-person inspections, saving time on site and reducing the need for heavy manual handling. Routine maintenance can be completed faster and with less disruption to traffic or surrounding works.

By removing the need to lift large, heavy covers, the inspection window also helps minimise health and safety risks for operatives. It enables early detection of blockages or water build-up, improving asset management and reducing costly unplanned interventions.

Hercules eye bolt lifting point
Eye bolt

Lift Smart, Work Safe

The threaded lifting eye on Hercules manhole covers allows for safe, balanced mechanical lifting, removing the need for manual handling of heavy covers. Positioned precisely at the centre of mass, it ensures stable, level lifts every time. This simple feature reduces strain, improves operator safety, and speeds up installation and maintenance - making site work more efficient and compliant with best practice in manual handling.

Available options and accessories

Options

Accessories

Note

*Although covers above 1000 mm clear opening are outside the scope of BS EN 124:2015, Hercules has been engineered and tested to the same D400 performance criteria.

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Whether you are looking for live project support, or are in the initial stages of specification, we are always on hand and happy to help.