Case Study #1 - Cement
AKO Pinch Valves used in Cement Plant
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 efforts.
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 |
