Mechanical Tube Decoking
Mechanical decoking, also known as reaming or “turbining,” was once the standard method. It is seldom used now because of its slowness and high cost.
Advantages and Disadvantages
The advantage of mechanical decoking is that it will work when nothing else will, e.g., on a plugged tube. On the minus side, plug headers are required for regular mechanical decoking. Plug headers are notorious for their maintenance requirement and tendency to leak. Mechanical decoking is slow and labor-intensive, therefore expensive. The hardened steel blades of the cutter remove tube metal as well as coke, about 0.001 inch of metal per cleaning on the average, sometimes much more. See API Guide for Inspection of Refinery Equipment, Chapter IX, Figure 18, “Tube Damage Caused by Mechanical Cleaning Equipment.”
Use of plug headers requires header boxes on heater, scaffolding, the tools used for removing holding members and plugs, plug racks for segregating the parts for each header (they are not interchangeable), and machine shop and welding services for repair. The decoking equipment consists of compressed air hoses and a set of air driven mechanical cleaners.