Scarfing may sound like something your teenage sons do at the buffet line, but with respect to pipes, it has an entirely different meaning.
Tube scarfing is the process of removing the excess welding material from longitudinally welded tube or pipe to provide a smooth surface. Scarfing can refer to bead removal on either the inner diameter (ID) or the outer diameter (OD) of the pipe.
What is tube scarfing?
The scarfing process takes place immediately after welding so the material may be removed relatively easily. Thus it’s very important that a scarfing tool and the corresponding inserts be reliable and resist chipping and breaking of either the cutting surface or the tool itself. Time is of the essence should anything break and need replacement.
Tube scarfing tools with modular design allowing for easy disassembly and reassembly are especially helpful for the ID scarfing process, where it is necessary to deal with long sections of pipe that are inaccessible from the outside. Modules must be properly toleranced to allow for a solid fit that retains collective stability. Inserts must fit well and be easy to load and remove. Reliable interchangeability of modules can save you setup time and keep your scarfing system running smoothly.
Without a smoothly operating ID scarfing process, strands of the scarfed material may be left attached to the inside of the pipe, leaving a worse condition than the bead it was trying to remove. Worse still, this material may tangle into a “bird’s nest” of metallic slivers that can’t be removed from the pipe with any amount of clearing blowout force.
What about the inserts?
While the scarfing tools must be made of extremely hard materials to deal with the operating temperatures and metals to be removed, they can also be brittle. The inserts that you choose for your tool should be of the proper grade (hardness) and coating properties to cut the weld bead of your material as cleanly as possible without chattering or chipping. Specify the correct insert materials and coatings to fit your needs based on the materials you’re working with.
The amount of pressure exerted by the tool on the pipe is also an important parameter in maintaining a smooth pipe surface while extending the shelf life of the inserts or rings. Whether the system is mechanical or hydraulic, it should deliver the proper amount of pressure on a regular and consistent basis.
Remember, poor technique or handling/maintenance will shorten the life of even the best scarfing equipment. Just because scarfing tools are the least expensive components in the process doesn’t mean that they aren’t valuable. Take care of them and you will be rewarded with superior tool life.
Saar USA carries a sturdy line of tools and accessories for both OD and ID pipe scarfing, including blades/inserts, holders and cassettes for OD scarfing, towbars with impeders, mounting units, scarfing/cutting rings, and notching mandrels and bead chopper units to help in dealing with the removed materials. Customized scarfing systems for unusual dimensions and shapes may be available upon request.