The DDT Pigg ® - a compliant and flexible cleaning device - is the key to the DDT process. This polymer Pigg ® is available in diameters from 16mm (½"), to as large as 914mm (36"). It will negotiate short radius elbows, plug header and U-bends with ease, obstacles that have long defeated conventional pigs.
Each DDT Pigg ® carries an array of interchangeable cleaning appendages or studs, each of which is threaded into the body of the pigg ®. These cleaning appendages are radially dispersed in a clockwise or counter clockwise pattern to provide a complete 360° cleaning action. The Pigg ® size, the number of studs, the stud material, the geometry and the height are all matched to each stage of a cleaning run.
It is the ONLY Pigg ® design that incorporates interchangeable appendages. This patented design enables the operator to adapt to all conditions encountered in refinery heaters, thus providing optimum cleaning performance in the shortest possible time.
DDT Pigg's ® are available in various sizes, shapes and the appendages in a range of hardness. The selection of the appropriate Pigg ® and corresponding appendages are determined by the following factors:
- the deposit hardness
- the extent of coke build-up
- the location of the deposits
- and the specific pipe material.
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DEPOSITS FROM PREVIOUS DECOKING ATTEMPTS
DDT has encountered many furnaces in which deposits were left behind from previous pigging decoking attempts. DDT has also removed steel shot that remained in the tubes from previous cleaning attempts. Deposits that are not completely removed from these tubes will accelerate the onset of coking, which in turn will shorten the run-length. Coke samples that were analyzed, revealed that the DDT pigging process is capable of removing all deposits and coke build-ups left behind from steam-air decoking, chemical cleaning, pressurized shot cleaning or inferior pigging.
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