How Olive Furnace Worked
At Mt. Olive Charcoal Iron Furnace there were three levels of operation: the ground level; the top of the cupola (Stack) level; the ore and charcoal level. When the Charcoal, limestone or iron ore was brought onto the furnace site, it was weighed at the company store - wagon, oxen / mules and the load. After the weighing, if it had a load of limestone, it was taken to the second level and off-loaded at the stockyard building where the limestone would be broken into smaller chunks by a man and a sledge hammer. It was then shoveled into an open bin in the stockyard shed waiting to be charged into the furnace.
All charcoal / brands, was off loaded on the third level near the top of the ore burners. Good charcoal would then be sorted from the brands. Good charcoal was wheeled to the shoots on the charcoal house roof and slid down the shoots to the second level, Brands and poor charcoal was stacked at the ore burners (Geirs Kiln). The ore burners consisted of a round, metal tubes that were 20 feet in diameter sitting on the one open end. It had openings along the side going to the top for air induction. The bottom had a large opening that closed with a door lined with firebrick. The entire inner wall of the burner was lined with fire brick. All of the ore brought in was deposited near the burners. No raw ore was placed into th furnace. All of the ore and charcoal for the ore burners was broken into smaller pieces. There were several reasons for this, but I will only name two. Ore not broken into smaller pieces could possibly break the firebrick lining of the ore burner and also would not burn as well. Charcoal burned faster and gave more heat when in smaller pieces.
The ore burners sat on the second level extending upward over the top of the third level. The charcoal and brands along with the ore was charged into one of the ore burners in four places around the top of the burner to assure that all of the ore and charcoal did not pile up in the same place; hence the need for the scaffolding around the top of burners. A tier of the charcoal/ brands was the first layer and then a tier of ore. These alternate layers were charged into the burner until it was full. The brands/charcoal were set afire and let burn until it was completely burned. This took most of the impurities out of the ore and made it a better grade of ore.
There were open ports along the side of the burners in various locations to allow more oxygen into the burner so the contents would burn faster and hotter. Once the burn was finished the opening at the bottom of the burners was opened and the semi-molten ore would pour out. The ore was cooled with water and broken into small pieces and taken to the storage shed and put into open bins awaiting charging into the furnace.
This charcoal was stored in the storage shed. This brought all of the burden to the second level and handy for charging the furnace.
The furnace was charged from the top of the stack, through a trap door, at the end of the boilers which sat on top of the stack and arch. Measurements of the burden were made by two wheeled metal carts. They were made of iron because wooden carts would burn when they dumped their load into the furnace. The charge consisted of so many full carts of charcoal, so many full carts of burned ore and so many full carts of limestone.
The cupola sat on the first level. At Olive the lower part of the cupola was carved out of the hillside sandstone. The upper portion of the cupola was constructed of hewed sandstone blocks. The lower portion of the cupola was also one half of the abutments for the two Roman Arches.
Before the charge was placed into the furnace, a fire clay ball was formed in an iron pot made for that purpose and forced into the maw of the furnace to keep the iron from coming out while it was smelting.
The furnace was generally charged every thirty minutes of operation and tapped every12 hours. The intermediate charges were made the same way as the original one was made.
The tapping was done by two men holding a long iron bar onto the clay ball, which was now brick. A third man would then hit the end of the bar with a large sledge hammer and brake the ball. The molten iron came flowing out onto the hearth of the furnace and then passed the dam stone into a trench that was in the center of the casting house known as the sow. From the sow, smaller trenches were made that directed the molten iron into the pig molds. Other molds- usually stove parts, railroad car wheels, frying pans, Dutch ovens and other things that were needed had the molten iron poured from a ladle directly into the mold. The pig iron was stacked in front of the casting house waiting for shipment.
When the iron had finished pouring, the slag was channeled to the other side of the casting house where a chain was thrown into it. When the slag cooled, the chain was caught in the slag and by using the slag wheel ,the slag could be pulled to the front of the casting house where it could be broken up, placed on wagons and hauled away and dumped.
Things were always breaking, so a carpenter shop with men to repair whatever needed repair was built. The blacksmith was kept busy shoeing mules as well as other things that needed his attention. The carpenters were kept busy replacing wood in the buildings that had been destroyed by fire or termites.
There was a water well in front of the casting house, close to Olive Creek, that supplied water to the 2 boilers and tuyeres. This water was pumped by a steam engine and a water pump into two iron water tanks that lay on the ground on the hill just above and in back of the engine room.This water was under pressure and sent to the boilers when they needed water. The need for water in the 2 boilers was indicated by a thick glass tube that was placed on the side of the boilers at the water line.
Water was also needed to make the molds, to cool the pigs, to cool the burned ore and keep the tuyere nozzles from melting. The tuyere nozzles were the place where the hot air was pumped into the fire to make it hotter by supplying more oxygen. There was a constant stream of cool water running through the tuyeres all the time the furnace was operating. The water going into the tuyeres turned to steam and was discharged through the side of the stack at the tuyere openings. If any one needs to know the water changing from a liquid to a gas is what cooled the tuyeres. The tuyere nozzle itself was made of brass and hollow for the water to cool it so it would not melt.
The air for the blast was pumped by an air pump in the engine room, to the blast heater that sat on the hill behind the boilers and the Roman arch. From the blast heater(18 pipe Player blast heater) , the hot air was forced down to the two tuyeres on the furnace. The pressure of the blast at the tuyere was 3 1/4 pounds per square inch and the temperature was 800 degrees.
Information concerning the working of the furnace was acquired primarily from people whose ancestors worked at the furnaces, charcoal iron furnace historians and written general history of the iron furnaces of the time et al. Stout, Wilbur, The Charcoal Iron Industry of The Hanging Rock Iron district Overman, Frederick, The Manufacture of Iron.
Copyright 2008 by Amos Hawkins All Rights Reserved.