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JULY-AUGUST 2013
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COMPACT CRUSHING
that require increased use of high-quality
aggregates, it added.
BHS offers machines in four different sizes
for throughput rates of up to 400 tonnes/hr.
It said crushing with BHS impact crushers
with vertical shafts and twin-chamber rotors
was a popular choice in many plants for the
production of high-quality aggregates.
BHS rotor centrifugal crushers adopt
the impact crushing principle. The material
is fed vertically from above onto the high-
speed rotor, which is mounted on a shaft
with vertical bearings. The company claims
maximum input grain sizes of up to about 80
mm (3.2 inches) for hard rock and up to 150
mm (6 inches) for soft rock; optimal material
flow in the rotor, free from clogging; and 15
to 20% greater throughput rate with the same
power consumption.
DESIGN IMPROVEMENTS
Glen Creston claims to have improved the
design and function of its roller crusher that
can be supplied with a new control box with
a PLC, which allows remote monitoring and
control of the crusher in process applications.
The largest single shaft unit is now 800 mm
(32 inches) long by 500 mm 20 inches) wide
internally, and designed for crushing lump
coal up to 250 mm (10 inches).
Described as a rugged, slow-running
mill, it is equipped with either a single or
double roller shafts fitted with crushing cams
that rotate between crushing and stripping
combs. Different shaped crushing elements
are available depending on material.
Island challenge
One of Scotland’s most inaccessible and environmentally-sensitive nature reserves created
some logistical challenges for specialist civil engineering firm Hatrick Bruce, part of Purvis
Group, which has completed demolition and crushing works on the Isle of May.
The island lies some 7 km offshore in the Firth of Forth and is an important research
centre for breeding seabirds, and home to a large colony of grey seals.
The contract with Scottish Natural Heritage (SNH), which manages the reserve,
involved a military-style approach to planning to bring heavy plant onto the island to
demolish, crush and screen a large concrete structure that dated back before World War
1 and which was beyond repair. It was all part of SNH’s plans for its new visitor centre.
In a four-day project, Hatrick Bruce commissioned Briggs Marine to bring in heavy plant
and equipment that included a 20 tonne JCB excavator, hydraulic breaker and crushing
units, dumper and twin skin fuel bowser by barge – a very delicate operation given the
extremely difficult landing and access facilities.
It was not possible to land large crushing equipment – in fact various attempts had to
be made before the right weather and tide conditions were met for the right length of time
to land the other machines. The decision
was made, therefore, to use a crusher
bucket, and an MB BF90.3, weighing about
2.5 to 3 tonnes, was chosen
Demolition was carried out progressively,
starting at the entrance and moving
through the building so that waste materials
could be processed systematically.
No additional quarried aggregates were
shipped in and brought on-site, and no
waste demolition materials were shipped off
the island, with the exception of aluminium
and wrought iron.
The crushed building was processed to
provide the right grades of hardcore for
SNH’s new visitor centre and for footpaths
on the island. Crushing and screening had
also to be carried out in such a way as
to minimise dust, again by creating the
precise grade of aggregate. The choice of
equipment was central to creating the right
product – aggregate had to be no larger
than 70 mm (2.8 inch) and all the concrete
was double-processed.
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The Anaconda SR514 is the company’s
largest machine to date
The crushing function of the BHS rotor
centrifugal crusher with rock shelf by
means of the rock-on-rock principle
