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Glossary of terms

Captive hinge

Integral hinge feature which allows easy access but resists total unauthorised removal of cover or gully grating.

Safety keyway

Safety keyway are a unique feature to Wrekin Products which ensure standard lifting keys are retained securely in a keyway, whilst the cover is lifted.

Chequer pattern

Integrally cast raised pattern on the top surface of manhole covers.

Clear opening

EN 124 defines the clear opening as the largest circle you can enscribe within the frame.

Double triangular

Covers or gratings formed from two triangular units giving stable seating under load and non-rock performance.

Indexed covers

Ensures covers can only be installed in one orientation.

Kerb hinged

Hinge located adjacent to the kerb.

Keyways (closed)

Blind lifting pockets in covers for lifting keys which prevent ingress of coarse debris.

Keyways (open)

Lifting keyway holes in covers for lifting keys.

Mortar sympathetic features

Design of frame and cover features that reduce the strain in the foundation bedding material, enhancing ironwork performance and longevity

Loosely coupled

The two half covers/gratings of double triangular units are connected together loosely by pins and clips. This helps prevent covers/gratings being dropped in the shaft during lifting and, being a loose connection, still allows the two half covers/ gratings to operate independently and retain their non-rock facility.

Non-rock

Cover/grating and frame design which gives quiet stable seating i.e. double triangular.

Prising slot

Slot in cover edge or occasionally on inside of frame that allows the use of a suitable prising bar to loosen covers before removal.

Safety grid

A fabricated grid, which normally drop-fits onto the frame below the cover to provide a safe working environment and to prevent covers and other objects being dropped into the shaft.

Set

Two triangular covers together are often referred to as a set.

Seal plate

Removable plate installed under the manhole cover as a protective barrier against water ingress, water egress, sewer gasses and condensates.

Solid top

Continuous top cover. Not a recessed cover or a grating.

Seating

Bearing/contact area between cover and frame.

Single-piece

Cover/grating comprising one piece.

Ventilated cover

A cover with openings that allow the possibility of free air circulation within the shaft and to reduce pressure build-up or the concentration of explosive or noxious gases.

Waterway area

Free area of grating which allows the passage of water (ie. total area of slots).

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