Fitting and Welding and Welding and Fitting

I was working with Jordy yesterday helping to fit up some wear plates. I like fitting as not two plates are the same. Jordy is a quasi gypsie/welder/surfing instructor slash, slash, slash. He is also lots of fun to work with. I'll tell you more about him a little later but first I want to tell you about the work we were doing. Inside the surge bins the walls are a double layer of steel. The first layer is the frame of the thing and the over the top of that is a layer of wear plates. Wear plates are designed to take the abuse of however many thousands of pounds of bitchumin-rich sand pressing and grinding against them every day of their working life. Eventually they wear out and the plant goes into shut-down mode while they are removed and replaced. Without them a new in would have to be built every year. So they are an important part of the process. You will recall (if you have been following this blog) that a few months ago I worked with JD, Alvin, Matti, Ryan and a few others fitting the lugs onto these same wear plates. Now the Ironworkers have 'flown them in' with the crane and they have been tacked in a couple of spots into place. But they have not been fitted to the steel walls that they will live on for the rest of their working lives. That is the job we are doing now using stick welding and a team of welders is following us completeing the process by doing a total weld out using flux core (wire) welding machines. We fit they weld. The process for Jordy and I starts with me using the tiger torch to heat the steel to 200 degrees plus. The tiger torch is a little propane flame thrower which is a god send in the winter but on hot summer days often seems hell-sent. I hit the corners first and then in a few inches because that is where Jordy tacks on the dogs and hammers in the wedges. Confused? Let me explain... No piece of metal is perfectly flat. We are fitting the wear plates over welded seams in the underlying plate and those seams aren't always perfect matchups either. But for the wire-feed welding guys to do their job successfully the plate must be snug to the underlying surface in a tight fit. Ever tried to bend a 3/4 in piece of steel plate? It is a tough thing to do. So the fitter uses a square piece of plate turned on its thin edge and with a small notch cut into one corner. He tacks this to the parent metal on the piece above, below or beside the piece being fitted so that it overhangs the place where the piece being fitted is not tight to the metal underneath. Then a wedge made from the same heavy plate metal is placed over the piece being fitted and into the notch. This wedge is probably about 9-12 inches long. It is then hammered under the notch in the dog forcing the metal beneath to flatten tight to the metal beneath. The fitter then tacks the piece to the parent metal holding it in place. He does this to every part of the plate that is not snug to the piece below often resulting in several dog and wedge combos being used on one plate. Once the piece is tacked in the wedges are knocked out of the dogs and the dogs are knocked of the plate and then the whole process is repeated on the next plate. Hopefully I have pre-heated that plate by now and while Jordy starts on the next one I go back to the one before and add some 'post heat' to the welds. There are good reasons for pre and post heating. In theory (keeping in mind that I am not yet an expert) pre heating accomplishes a lot. It first removes moisture from the surface of the plate making the weld stick better. It prepares the carbon atoms in the metal for bonding better by allowing hydrogen atoms in the metal to escape. Simply put it reduces the chance of the weld cracking. The post heat does the same thing as it gets the hydrogen atoms out which would otherwise crack the weld later when escaping from the carbon atoms. When the welds go on these huge metal plates it is like a big drum bing hit as it makes a deep 'bowang' sound. Well that's the process and I am out of time. I'll have to tell you about Jordy another day! :)