In many designs, pipe or tube jackets/sleeves are required to perform a specific function that standard mill pipe cannot perform, nor any other standard steel mill shape. Used in such applications but not limited to reinforcing existing pipe and/or used in heat transfer systems, pipe jackets/sleeves are becoming more commonly specified by design engineers for their strength and load/force dispersing capabilities. In some circumstances where the diameter of the jackets or sleeves are very specific, they need to be formed from plate but that is an expensive, labor intensive process. A cheaper more efficient alternative to formed jackets/sleeves is to obtain them through splitting & straightening pipe or tube. In either circumstance, a bender/roller must be contacted as formed jackets must be bump formed on a press brake, and jackets from split pipe must be straightened after being split since residual stresses cause split pipe to twist in an undesirable manner.
Splitting of steel pipe or tube is done through a flame cutting or plasma cutting process. Most all pipe sizes through 30″ XH can be split and straightened except for the extremely small diameter, thin walled pipe. Specific jigs are used to hold the pipe/tube in position as the flame or plasma cutting is taking place. Due to the nature of mill-produced steel pipe or steel tube, residual stresses are built into each pipe; when splitting preventative steps are needed in order to inhibit the pipe from springing open which can cause the cut to stray from straight. Each pipe or tube is cut twice down the entirety of its length, once on each opposing side rendering two half pipes of 180degrees out of a 360-degree standard round mill pipe or tube. After the pipes/tubes are split, they must be straightened in order to remove any twist caused from residual stresses as mentioned previously. The straightening is done by a bender/roller as this type of specialty fabricator has the necessary equipment to successfully straighten the split pipe or tube jackets/sleeves back to within mill tolerance once they are split.
Once the jackets/sleeves are straightened, they are then shipped as is or cut to length and shipped. In one application,the pipe jackets will be used as reinforcements which will be fastened around pre-existing pipe with U-bolts. The pre-existing pipes are structural legs of Exelon transmission towers. With the expansion/upgrade of our nation’s power gird, more cable is being run along these towers with the increasing loads causing a need for structural reinforcement. In other applications where pipe or tube jackets will be used in heat exchangers, they are then rolled/bent to a specified diameter with either the toes in or toes out, and are usually welded to the inside or outside of a vessel. Coolant/liquid is then run through the jackets in order to aid in the heat exchange process.