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Round E400

Strength by design!

Terra Firma E-Class Thrubeam Range are the most advanced in-road lid on the market. Terra Firma Heavy Duty Thrubeam access covers offer strong, lightweight covers for in-road applications including high traffic freeway areas.

Terra Firma Thrubeam access covers have been developed to give optimum performance and are significantly lighter than concrete and ductile options.
Produced under carefully controlled manufacturing conditions our covers are precision made to ensure the highest quality fit between lid and frame. This means less wear and the elimination of a major cause of failure of ductile iron lids.

Our Thrubeam manhole covers are produced as a singular monocoque construction giving integral strength by design. Terra Firma Thrubeam composite range is robust and will not crack, warp, chip, swell, or expand. The stiff tensile structure resists all known forces under normal working conditions. Tensile stiffness is 4-6 times that of steel or aluminium. They are suitable for in road applications and are independently tested to meet all standards of AS3996 D & E Class.

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High structural performance

Structurally and fatigue tested. Meets AS3996 D & E-Class, AASHTO and European EN 124 D400 regulations.

Extended working life

Composite covers continue to perform well after 20 years in service. Will not break or spin out. The torsional resistant frames eliminate many of the usual causes of wear with traditional covers.

Permanent anti-slip

Exceeds 0.60 co-efficient of friction even when wet and will retain this anti-slip value throughout its working life.

Secure and lockable

Additional security may be included through a bolting system that automatically disengages when the cover is removed and reengages when replaced. High security key option is available.

Injury free removal

Single person removal and replacement without risk of injury. No need for any additional lifting equipment.

Reduced maintenance programmes

Longevity, ease of moving and superior performance reduces maintenance programs. Fitting a Terra Firma cover is the best ‘whole life’ choice.

Sealing (optional)

100% watertight/sand tight with an unique self cleaning edge seal.


Covers can be vented which helps prevent the build up of explosive gases. Holes conform to ADA regulations.

Transparent to radio waves

In pit radio transmitters are easily monitored through lids without the need to open pits.


Will not corrode when in contact with other materials. Unaffected by sand, salt and all chemicals met in road environments.

Electrically non-conductive

Will not conduct electricity, so stray voltage problems are negated.

Client design service

Terra Firma project managed bespoke design services will use our patented technology to design alternative size and shapes solutions to meet customer requirements.

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