Case Study #1 - Cement
AKO Pinch Valves used in Cement
For over 15 years, AKO pinch valves have been used
successfully by Blue Circle in the manufacture of cement.
In the mill house, which is unavoidably an environment
of high temperature and abrasive dust, the standard
rubber sleeves in the pinch valves last for at least
18 months before routine replacement.
At the Hope Valley (England) cement works, in the mill
house where limestone clinker is milled into cement,
at normal temperatures of 2200°F, the elevators
transport finished cement at rates of 200 tons/hour.
Entrained in the cement are small numbers of nibs milling
medium (17mm manganese balls), These are removed at
the head of the elevator, where the cement enters a
centrifugal separator, via a nib trap, where the nibs
are extracted from the flow of cement.
The collected nibs are conveyed through an air slide
incorporating an AKO pinch valve. The discharge side
of the valve empties onto a vibratory screen where any
stray cement adhering to the nibs is filtered back into
the elevator. The used nibs are then dumped. By the
time the nibs pass through the pinch valve they have
absorbed heat from the hot cement but their temperature
is still below the allowable range of the high temperature
pinch valve sleeves.
Two 600 HP cement mills together use four elevators,
each equipped with 8 inch pinch valves, giving a combined
production of over 200 tons/hour.
Because of the high operating temperatures the pinch
valve sleeves are exposed to, the Blue Circle maintenance
engineers routinely replace the sleeves at intervals
of about 18 months, Any inadvertent increase in cement
temperature could have a baking effect on the rubber,
thereby shortening its life. AKO engineers are presently
working to develop an alternative sleeve material which
will extend the working life and reduce maintenance
Elsewhere in the plant, other AKO valves are used.
The 500 ton capacity storage and discharge silo loads
outgoing cement into rail wagons. The conical lower
section of the silo is equipped with aerator lines to
assist gravity flow. Divided into 4 circumferential
sectors, the aerators operate sequentially on a timer,
using sixteen 2 inch diameter AKO valves to control
the bursts of compressed air.
For more information on AKO pinch valves and accessories
please call +614.873.8995