The patented ‘no-gap lid’ manufactured by high-tech
reinforced concrete products developer Concrete Doors & Vaults, in
Roodepoort, is the solution to the endemic vandalism of valve chambers in South
Africa, says team leader Dr Nicholas
Papenfus.
Steel lids are easily vandalised, as the locking
bar positioned over the lid can be cut off, leaving a valve chamber vulnerable,
he says.
Concrete Doors & Vaults was established in 2015
out of demand for anti-theft and/or vandal products.
The company offers several effective
vandal-resistant solutions; among them a no-gap lid seated in a precast slab
for new valves chambers and a no-gap lid in a cover slab for existing valves.
With the no-gap lid, vandals are unable to insert
picks or levers, as the sides of the manhole opening and the lid are both
inwardly sloped such that, when the lid is seated in the slab, there is no gap
between them. The use of angle grinders on the locking mechanisms is also
eliminated, as the robust locking mechanism is attached to the bottom of the
lid.
“The opening in the slab typically varies from 500
mm X 400 mm to 600 mm X 500 mm, and the slab may be precast or integral,” he
explains.
To open the lid, the plug is removed from the upper
end of the access tube using a magnet at the top of the opening tool. The key
is used to unlock the cylindrical lock and remove it from the lower end of the
access tube.
Papenfus says: “The size of the cover-slab will
vary depending on the size of the manhole – generally the cover-slab overlaps
the manhole by 200 mm on all sides. The cover-slab is internally bolted to the
existing slab so it can’t be pushed or lifted off the existing slab. Only when
the no-gap lid is unlocked and removed can these bolts be removed.”
A central stainless access tube is provided for the
opening tool to engage the locking mechanism. The slabs and lids are
manufactured from highly chisel-resistant 60 MPa concrete.
The lid has four layers of closely spaced rebar,
such that the maximum passage between bars is 20 mm. “This prevents the use of
chisels during vandalism attempts,” says Papenfus.
The lid also has an exoskeleton of 3Cr12 (12%
chromium utility stainless steel) plates, which add further resistance to
chisels.
The access tube is closed at the top by a stainless
steel plug, and further down by a patented cylindrical lock.
All steel components are made from corrosion
resistant stainless steel – SS304 or 3CR12.
Concrete Doors & Vaults offers a range of
products that provide extreme protection against theft and vandalism of
vulnerable infrastructure in the water, power and telecommunications sectors.
The products are mostly made from heavily reinforced high strength 50/60 MPa concrete, and include sliding doors for securing pumpstations and sub-stations, vaults for securing boreholes and control panels, and ventilation panels for generator rooms. https://www.engineeringnews.co.za/article/concrete-doors-vaults-no-gap-lid-keeps-vandals-out-of-valve-chambers-2019-08-20
