In the last post, I wrote about flipping heads with an overhead crane. So I thought it time to write about cranes. Here is a drawing of one kind we have in our shop.
The grey tracks are mounted near the tops of the walls. The two yellow beams, the bridge, travel along the tracks. The blue trolley moves along the yellow beams in the opposite direction. The orange hoist is raised and lowered on cables. The small yellow rectangle suspended from the crane on a single cord is the control box. Here are two photos of overhead cranes similar to ones we use.
Here is a brief video (with audio) covering three types of cranes. The bridge crane is the overhead crane I am posting about. We also have a jib crane at each flanging machine. We don’t use the other kind of crane.
Flipping heads is the most difficult operation we use these cranes for. Some machines are loaded via bridge cranes, although most are loaded by forklift. Shipping uses them to stack heads in preparation for loading onto trucks. They are used to lower and raise heads into and out of the pickle tank. They are also used to lower and raise annealed, or heat-treated, heads down into and up out of tanks of water. When a large water-quenched annealed head of several thousand degrees is lowered into water, it’s quite a show. The red-hot metal pops and cracks loudly as it quickly darkens, and the water bubbles and a thick cloud of steam billows up all around the head.
But what I use an overhead bridge crane the most for is separating heads. Multi-piece orders are stacked inside each other after they are pressed. Often the press operator will press two or three heads at a time. When that is done the separate heads are tack-welded together, to keep them aligned while in the press. A tack-weld is a small temporary weld, one that is easily broken and ground off once the press operation is complete. Press operators can do up to four heads at a time, but we have to flange them one at a time. To separate tack-welded heads, I drive a wedge between two heads at a place opposite the weld, slip a clamp onto the top head, then lift it up out of the stack by crane, breaking the weld in the process. With smaller heads I can do this with the jib crane mounted at my machine. But for larger heads I use the overhead bridge crane.
All our cranes are inspected regularly. We visually inspect the cables for wear daily. But things still happen. I was operating an overhead bridge crane once when the trolley motor decided to come down. It hit the floor about five feet away from me. It would have killed me if it landed on me. Another time someone was flipping a big heavy head when he allowed the head to jerk the crane too hard. The trolley was jerked right off the bridge. The head had been standing on end, so as it fell the end nearest the floor swung up, like a teeter-totter. It caught the trolley as that fell, hitting it with so much force the trolley shattered, sending steel fragments flying all through the shop like missiles. Badeye happened to be walking by (some people are magnets for bad luck, don’t you think?) when he heard the explosion. So he took off running. He wasn’t hit by anything, but he ran blindly into a stack of heads, and got some lumps from that.
The most irritating thing about overhead bridge cranes is the brakes wear out. So they don’t stop when you release the control button, they just drift merrily on the way they were going. Lately the control boxes dangling from the bridge are being replaced with wireless controls. The trouble with these are you have to go search for the wireless box when you want to use the crane. With the old wired boxes, they were always hanging by a cord from the crane, so you always knew where they were. But that’s progress. Solve one problem, create a new one.
The jib cranes at our machines are used mostly for set up – changing out the icr rolls, raising or lowering the lower center post. We also can use them to separate small heads, and to load small heads in and out of our machines. They are now electric, like the overhead cranes. But they used to be pneumatic. Air lines can be tricky. They can leak, become clogged with oil, the pressure raises and drops unexpectedly. Electric is much more reliable. But they ran on air at the time Brent C. crushed a finger using one. He was a spinning lathe operator who became a flanging machine operator who became an inspector who became a foreman, and, also, was union president for a while. An interesting guy. But at the time of the accident he was running a flanging machine. He was taking a head out of his machine with a jib crane when it kept going up after he released the control. The valve stuck. He was holding the top of the head, guiding it out of the machine, when his hand was caught between the head and the machine. He nearly lost a finger. He said later it would have been better if it had been cleanly cut off. They managed to save it, but he claimed it ached so badly he wished they hadn’t. You have to know where your fingers are at all times. There are so many pinch points on a flanging machine. I never place my fingers in a place where they might get caught like that. While running a flanging machine you have to stay on your toes. If you want to keep all of them.