A major artery found in all oil/gas refineries, chemical plants, energy/power plants even in food and beverage processing facilities and often in many vessels/ships, is the process piping system. These systems are vital to the handling and transporting of product to the different processes taking place within the plant/facility, as the process piping system is essential in carrying and transferring liquids, gases, slurries and or other fine particulates to be processed/refined further or be used for energy/power. The magnitude of these systems can be immense, with some facilities measuring the amount of piping in their plants in miles or kilometers rather than in meters and feet; imagine a spaghetti bowl with order, control, and clearly designed patterns to allow flow like a neatly designed traffic system. These piping systems are so important and so complex they require their own supporting engineers to design and assist in the proper transportation of certain gasses and chemicals and in the sequence of construction/assembly of the piping system itself. Within this venous like network of piping, which twists and turns and weaves its way up, down, left and right throughout the plant, there are individual pieces to the whole or the puzzle if you may; these segments of the piping system are between flange connections and are prefabricated segments containing multiple elbow fittings welded to straight lengths of pipe to create Tetris like puzzle pieces; these segments are called “SPOOLs”.
The spooling of these piping systems are extremely important as field welding/assembly all of these individual pieces and components would be insanely time-consuming and difficult considering the environmental control issues and the amount of welding required, not to mention what orientation and positioning the welding would have to be done it. Combining bends and straight runs of pipe into one single “SPOOL” that can be prefabricated indoors makes much more sense in the construction of these systems. Required sizing for the piping within these process systems vary from plant to plant and from system to system but range from common off the shelf commodity sizes/diameters to non-commodity custom sizes/diameters and from very small pipe-like ¾” Sch 40 pipe all the way up to and sometimes exceeding large heavy wall pipe like 20” Sch 160. It is in these larger diameter spools that bender/rollers see a greater demand to have the spool bent instead of fabricated or welded. Smaller pipe sizes can also be bent into spools but fittings for these sizes are common as shelf stock from pipe flange and fitting suppliers and the welding/assembly is less demanding. With larger pipe sizes/diameters the welding/assembly is much more demanding and if the elbows/fittings are not available from a supply house they will then need to be formed by a bender roller, so why not request to have the complete spool bent or as much of the complete spool bent in a single piece as possible? With today’s advancements in CNC equipment/tooling and in alternate bending processes and methods, bender/roller have the capability to perform multiple bends in any number of different directions within a single length of pipe….limitations exist with respect to each bender rollers equipment/capabilities.
Two types of bending processes are most commonly used to bend pipe spools and that is either the bending takes place with the member at room temperature, which is commonly referred to as cold bending, or the bending is done at elevated temperatures, where the pipe is heated or it is done hot. To accurately perform multiple bends skewing off in multiple planes within a single member on older manually operated mandrel pipe bending machines is possible with highly skilled operators but with tolerances growing ever tighter and a need for documented quality checks/control a CNC mandrel pipe bending machine is the ideal machine to use if doing the bends cold. These machines are commonly used for pipe sizes up to and including 6” Sch 80 although larger CNC mandrel pipe bending machines have been custom made for pipe up to 14” and larger commonly for shipyards. These machines have been making reliable high-quality bends for years. With the use of a “full” set of bending dies; wiper die, mandrel & pressure-assist die added, these machines are capable of producing bends up to and including 180deg of rotation on relatively thin wall pipe….think sch 5 and or sch 10 Due and thinner on some tubes. The bend radius is dependent on the size of the bending die used. Due to these machines numerically controlled capabilities over push and turn collet/type units mounted to the rear of the machine they have the ability to advance material very accurately into the rotation bending die at the head of the machine while the dies are unclamped, this allows for numerous bends to be made along a single length of pipe at any given position along the length of that pipe. The collected advancing mechanism at the rear of the machine also has the ability able to rotate or turn the pipe in between bends and maintain an accurate count of which direction clockwise and counter-clockwise it has turned. This added capability now allows full complex pipe spools with multiple bends skewing off in different directions to be bent with very precise accuracy and control. Accuracy on these machines measures anywhere from 1/32-1/64” on advancement and 0.1deg on rotation. This type of CNC mandrel pipe bending produces quality repeatable bends that no doubt save time and money over pre-fabricating/welding the pipe spool.
On the other end of the bending process spectrum is hot bending; there are some hot bending processes that entail using an oven to elevate the temperature of the material but those methods are inefficient with respect to the bending of pipe spools. The hot bending method that is ideal when considering the geometry and shape of pipe spools is Induction Bending. Induction bending per its name utilizes electricity that runs through an induction coil which is offset from the OD of the pipe; current is then optimized at specific frequencies/amplitudes and due to the ferromagnetic properties of the material being bent and the electrical current being sent/passed over it an eddy current is generated from within the member itself, and any part of the member exposed to the backside of the induction coil instantly turns red hot. It is important to note that heat is not applied rather the excitation of the atoms/molecules within the material is cause for the increase in temperature. Induction bending is touted for its ability to bend very large sections with little to no change to their nominal pipe/tube diametral and wall dimensions during the bending process. This is due to the coil design which allows for heating to take place in narrow bands along the circumference of the material, ultimately allowing the bending moments and yield area to be constrained to this rather narrow heating band, thus eliminating the distortion issues seen in cold bending. Any time pipe gets larger than what your typical 6” cold bending machines can manage; induction bending is a great option to use for bending pipe spools. Current typical induction bending machine designs does not allow for the pushing mechanism at the rear to turn/twist so bending pipe spools with this process is definitely more involved when having to make bends skewing off in different planes but the machines ability to advance, stop/set, unclamp, manually rotate and then re-clamp does allow for pipe spools to be bent in this manner. Some induction bending machinery does have specialized software and mechanism to assist with the accuracy in bending pipe spools. Induction bending machines have been known to bend 60” OD pipe and larger.