Putting a Mountain Through a Sieve: The Cement Manufacturing Process

In the early days the limestone was quarried at the Bamberton site, but later when the Cobble Hill quarry was purchased the quarried limestone was transported to the plant by trucks, where it was dumped into the “Glory Hole”. It was fed into the primary crusher and withdrawn as required by remotely controlled feeders and conveyor belts to be further reduced by secondary and tertiary crushers and proportioned with the correct amount of sand. Finally, the mix was stored in one of ten raw mill feed bins. In the 60s the entire crushing operation from storage pile to feed bin was fully automated and watched over by closed circuit TV from the central control room.

Drawn from the bins, the limestone and sand were conveyed along with water to the raw mills…large rotating steel cylinders each containing approximately 25 tons of steel balls. Inside the cylinders the steel balls quickly pulverized the feed into a finely ground powder and 30 to 32% water was added, this thick white fluid was called slurry. From here the slurry was pumped successively into air-agitated storage basins where continual sampling, analyzing and blending was carried out. It was thoroughly mixed by revolving paddles set under a rotating platform.

The slurry was then pumped to the kilns. It was fed into the high end of the kiln at a constant rate where it took three hours to work its way through. The long steel cylinder lined with firebrick rotated slowly on giant rollers and moved the material continuously towards the lower or discharge end. The slurry was first dried out which produced some 750 tons of water per day that was evaporated and discharged through the stacks. The drying process generated large amounts of dust.

"I can remember a Mr. McAlpine used to pick up the lime dust and sell it to farmers all over Southern Vancouver Island to use as fertilizers."
(AE)

"Our house in the village was always dusty. My mother hated the dust but she used to say Bamberton dust is our bread and butter so we shouldn't complain."
(Bernice McCauley)

In 1967/69 electrostatic precipitators were installed that acted like huge dust magnets. The precipitators, which were the most modern in the province, reduced solid pollution by 99%.

The temperature of the kiln was maintained by the combustion of fine, dry coal dust, so fine it acted as a gas, which was fed into the cylinder by a blast of air. Later bunker C oil replaced the use of coal. When the temperature rose to 2300deg. F chemical reactions commenced among the ingredients and they fused together to form "cement clinker'. The hot clinker in the form of small black nodules was discharged from the lower end of the kiln into air coolers where its temperature was reduced to 200 deg F. It was then conveyed to a covered storage area.

The last step in manufacturing cement was the finish grinding. The clinker was first recovered from the storage area and fed into a cone crusher for reduction to a 3/8 inch screen size. The crushed clinker was then conveyed to one of two 5,000 barrel silos used to feed the main finishing mill. One % gypsum was added to retard the setting stage and then these two ingredients were fed to the finishing mill, a large rotating cylinder similar to the raw mill and containing 100 tons of steel balls.

Here the mixture was ground dry to an extremely fine powder that permitted it to pass through a screen of 10,000 apertures per square inch. A screen so fine that it could actually hold water. The finished cement was blown pneumatically to the storage silos for sacking or bulk shipment by road and water.

In the early days the cement was poured into barrels, later jute sacks sewn on site were used but these were replaced by heavy paper bags. Each sack held 87 ½ pounds, four sacks equalled the old barrel. Every 15 minutes in alternating shifts, workers filled 350 bags with cement hot from the silos.

"When paper bags were first introduced they would often explode, covering us with cement. This was because, unlike jute, the first paper sacks didn’t allow the air to escape when the cement was poured in."

The cement was shipped to market in the company's three boats, the Island King, Shean or Teco carrying 16,000, 10,000 or 6,500 sacks each.

"We used to catch a ride to Vancouver for the weekend on the Island King. One time the ship had picked up bed lice and we had to shake out the bedding. The smell of the spray they used to kill the lice was awful and we all felt sick."
(Joe DeLisle)

The quality of all cements produced at Bamberton was closely controlled on a round-the-clock basis. To carry out this control programme, two laboratories were maintained: a central laboratory run on a 7-day week, day-shift basis, and a control laboratory operating on a continuous three-shift basis.

As well as continual checks at every stage of manufacture, a complete daily analysis was made of all kiln feed.

Through its many years of operation Bamberton, maintained an enviable safety record and received the Safe Year Commemorative Trophy for many years running. The company offered incentives to maintain this good safety record and provided free safety boots to workers if they achieved an accident free year.

Click on images to enlarge

Tanks
Tanks
Kilns
Kilns
Aerial view of plant 1957
Aerial view of plant 1957
Clinker
Clinker
Covered storage are
Covered storage are
Finishing wet mill
Finishing wet mill
The Island King
The Island King
Laboratory
Laboratory
Safety boot award winner
Safety boot award winner
Safety team
Safety team
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