Fabrication starts with a build print and raw material handling. It ends with polishing and cleaning stainless to a shine.
Most of the tanks we build have several layers in the wall of the vessel. The shell is the inside layer of metal that has contact with product. This is usually the thickest layer to handle pressure or vacuum and support the weight of the tank. Attached to the outside of the shell is a perforated dimple jacket for circulating a temperature control media. That media is usually steam, water, glycol, or oil, depending if the tank needs to be heated, cooled, or maintain a specific temperature. We even use a mixture of refrigeration gasses in coils for cryogenic cooling. The next layer is insulation which can be mineral wool, ceramic insulation, board foam, or injected foam depending on the application. Finally the vessel is covered with a skin, or cladding, which is a thinner metal used to protect the insulation, keep moisture out, and give the tank it’s characteristic look.
CNC Metal Cutting
Cut files from the engineer get sent to our CNC metal cutting machines where we load the file into a computer and configure the optimal cuts to make into flat sheet metal. Flat sheet of stainless steel of various thickness is cut to shape and usually handed off to the forming area.
Most of our vessels are made in the shape of cylinders with either a flanged and dished head or cones for the ends. CNC cutting allows us to precisely cut ports into the cones or cylinder walls. This saves a ton of time from drilling or cutting into the vessels after they are formed. Plate rolls are used to make the cylinders, and our 250 ton press brake does the work of bump rolling pie shapes into cones.
Our two tools for machining are the basics of any good fabrication shop. A Bridgeport Mill and an Engine Lathe. For mass production parts we send off solidworks files to have them made repeatedly with CNC machining, but since most of our parts are prototype or “one off” parts, these two tools can make almost anything we need quickly and efficiently.
We use mostly GTAW (Gas Tungsten Arc Welding) also known as TIG (Tungsten Inert Gas) for most of our fabrication welding. Some structural or heavy welds are done with GMAW (Gas Metal Arc Welding) also known as MIG (Metal Inert Gas) or Wire Feed. TIG welding is great for leaving beautiful intricate welds. It’s also great for creating sanitary welds where product will touch the weld. Welding Stainless is somewhat of an art form. It takes a steady hand, precise speed control, and a ton of experience to get it right. Too hot and the chromium in the stainless evaporates out and leaves black “sugar”. Sugar is the industry term for failed stainless welding because it looks like burnt sugar. For piping and welding tanks that are too small to weld from the inside we use purge welding where a layer of inert gas insulates the weld from the opposite side of the torch.
A fabricator is more than just a welder. In our shop they operate all the equipment we have. They need to be a machinist, forming operator, welder, crane operator, and forklift driver.