Automated curing chamber simplicity ensures high quality concrete pipe
By Jim Bartley, C.E.T.
Fourteen cells, covering a floor space of approximately 700 square metres,
accommodate pipe, ranging in size from 300 mm to 1500 mm diameter.
There are no workers moving
products into position with
forklifts and cranes. The area is
clean, and a robot periodically
moves quietly, high overhead, transporting
reinforced concrete pipe to and
from curing chambers. The controlled
environment for producing concrete
pipe is almost dreamlike, as machines
seem to be running themselves. Only
when you focus on the control centre
will you see the panels of the fully
automated plant and two technologists.
This is Schlusselbauer’s definition of
simplicity, as ultra-modern machines
tirelessly produce one high-quality
concrete pipe after another in its Exact
2500 plant at Munro Concrete
Products Ltd. in Barrie, Ontario.
Covered curing chambers are
arrayed in a series of rectangular cells
with a standard dimension of 4750 mm
x 1160 mm x 2900 mm high. At the
plant, there are 14 cells covering a
floor space of approximately 700
square metres. The chambers are
designed to accommodate pipes ranging
in size from 300 mm diameter to
1500 mm diameter. They can hold up
to twenty-four 300 mm diameter pipe
and up to eight 1500 mm diameter. The
operators, who know which cells are
occupied along with the data associated
with the curing process, monitor the
content of each chamber. The monitors
depict the cells that are empty and
those with closed lids. Curing is critical
to the strength, impermeability and
finish of the precast product.
The curing system allows the plant
to run in a closed loop. Moisture curing
starts immediately after a chamber
is filled with product, and depalletizing
of the cured products starts as soon
as the curing cycle is completed for
that product run. The rubber-sealed
chambers cannot be opened prematurely
allowing uncured pipe to be
removed. The system is pre-programmed
to ensure that chambers are
opened at the exact time when pipe is
cured to specification.
Schlusselbauer curing chambers are
designed to account for heat transfer to
the concrete pipe and the required
humidity. Heat and moisture balance
over the curing time is so precise that
floor dampness is negligible. The galvanized
structures of the chambers
resist corrosion that may result from
the curing process.
Curing cycles programmed into the
software and control system assume
that the ambient temperature in the
kiln is 21 degrees C. If the temperature
is more than 21 degrees C, the curing
cycle is running but the water heater
will not turn on. The software is called
Collector. When the lids are placed on
a cell, a signal is sent to the Product
Management System so that it knows
the curing cycle has started and that it
should start the curing cycle timer. The
Munro system has been modified to
intercept this signal and send it to the
Collector program so that it starts the
curing cycle and, if necessary, starts
the water heater.
Once the chambers are sealed, temperature
is gradually increased by the
Project Management System software
to about 63 degrees C at the end of the
cycle, thereby efficiently curing the
product and evaporating most of the
available moisture.
Munro reduces the relative humidity
in the kiln near the end of the curing
cycle. Since the cement has hydrated
and the concrete is cured, a high relative
humidity is not required. At the
start of the cycle Munro has at least
85% relative humidity and at the end it
is reduced to 55%. By controlling the
humidity within each chamber, the
plant infrastructure is not subject to
corrosion as a result of the post treatment
process. Approximately 100
litres of water are used in a six to eight-hour
curing cycle in each cell.
The urethane foam sandwiched
between the galvanized sheet steel of
the walls and roof of the chambers
ensures efficient heat transfer to the
product and not the surrounding ambient
air of the plant. Since they have a
low mass, the panels exhibit a favorable
thermal efficiency. Controlled
transfer and retention of heat in the
curing chambers throughout the curing
process ensures that the specified
hydration of each product is achieved.
Schlusselbauer’s curing chambers
are not pressurized and have little to no
maintenance. The only moving parts
are rollers in a side door to each chamber.
In winter conditions, maintenance
personnel do not have to remove ice
buildup on the system, or clean up drip
water. Since the chambers are insulated
well and sealed, they do not lose
energy and heat the plant unnecessarily.
The product has been produced
without the touch of human hands, and
each piece is identical to the last in
design and quality. The concrete has
set, and the product is ready for use in
a variety of applications.
Contact: Jim Bartley, 705-458-1700.
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