Sometime in the mid-80's, cadet engineers were assigned to our section of the smelter department for a few days, to observe firsthand the process of converting molten matte into 95% blister copper.
These bright young men were orientated by management in the various stages of copper smelting and refining; they were groomed to become the company's future supervisors and managers.
So, this day, the cadets, there were three or four of them, were observing the slag blow stage, wherein a huge volume of air is blown into the converter furnace, in the range of 35,000 normal cubic meters per hour, in order to oxidize and separate the iron content from the molten matte.
They were kind of mesmerized as they watched the punching machine in operation, unmindful of the ear-splitting noise.
The punching machine is a contraption used to regulate the volume of air blown into the converter furnace.
Once the air pressure increases and the air flow rate drops lower than 35,000 normal cubic meters per hour, the operator sitting inside it aims for the tuyeres, these are actually pressurized holes which line the sides of the furnace, and lets loose four punching rods, in a quick back and forth motion, at the touch of a button.
He does this repeatedly to four sets of holes simultaneously while the machine moves sideways from one end of the furnace up to the other end until the air pressure drops and the air flow rate normalizes.
One cadet sidled up to our leadman, whom I call Mickey(not his real name) and asked, "Dong, how do we know when to use the punching machine?" I don't know if he just wanted to make chit-chat or what, I'm sure they covered this topic already in the training center before they came over.
Maybe it's just human nature, but some of my co-workers, who were Japan-trained, were not too generous in sharing what they know of the finer points in the Converter process.
Mickey replied, " When your butt gets itchy...
" End of story.