How is a traffic light made
How It's Made - Traffic Signals
traffic signal polls must be strong
enough to bear the weight of road signs
street lights and of course traffic
signals the poles are also built to
withstand extreme weather conditions
such as high winds and heavy snow
accumulation traffic signal poles are
made of high-strength steel years of
weather exposure can cause corrosion so
the poles are galvanized on both sides
for protection each pole has a welded
plate to connect it to a perpendicular
pole the poles are made out of these
steel sheets the steel arrives at the
factory in one large roll they use a
decoy ler to unwind the sheet and
flatten it out then a shear cuts it to
the correct length
a computer-guided plasma cutter mark
short lines on both ends of the sheet
these lines indicate were to bend the
flat sheet to form a round pole
the machine cuts the sheet into a
rectangular shape or a trapezoid shape
if the pole will taper at the top
workers number the Machine lines with
chalk giving lines directly opposite of
each other the same number then they
transfer the sheet to a bending machine
called a press break
the press break bends the sheet along
the marked line to a pre-programmed
angle
workers use a digital measuring device
to make sure the first Bend is accurate
if it is they continue bending along the
remainder of the lines transforming the
flat sheet into a multi-sided round pole
now the pole moves to a welding station
or hydraulic rollers apply pressure from
both sides
this forces the edges of the sheet
together so that a welding head confused
the scene with molten steel at the same
time the head deposits a granular powder
called flux which prevents air from
penetrating the weld and weakening it
workers place the pole in a hydraulic
press so it doesn't warp as the seen
weld cools and shrinks
you
next a computer-guided plasma machine
cuts a connection plate out of thick
steel
the machine also drills holes for the
high strength bolts needed to attach the
plate to the traffic signal poll workers
Center the connection plate on support
place they've already welded to the pole
then they weld everything in place
next workers weld a baseplate to the
bottom of the pole it has holes for the
anchor bolts which are used for securing
the traffic signal to the street workers
inspect the welds with a testing device
it uses an electric current to
magnetically draw coloured powder into
any defective area the factory ships the
finished poles to a galvanizing plant
where they're dipped in a series of wash
tanks
the plants tanks are deep enough to
fully submerge the poles so they can
treat both the inner and outer surface
at the same time
now the polls go into a vat of sulphuric
acid this baths dissolves the more
stubborn contaminants that washing can't
remove the next tank contains a chemical
that weakens the surface of the polls
this allows the galvanizing metal to
penetrate the steel rather than sit on
the surface
the final tank contains molten zinc
as the poles bathe in the 842 degrees in
workers and fire protection suits skim
the surface to remove iron oxide and ash
that floats to the top this keeps the
freshly galvanized surface clean as the
poles are hoisted out of the tank and
set aside to cool
because they're galvanized rather than
painted these poles are able to support
traffic lights signs and street lamps
for 40 years or more
