TPT September 2013

Article

OTO SpA

mill setting, permits correction of tube dimensions without stopping the mill (and originating scrap).

data available to an exernal SCADA systems for further processing and recording. Complete SCADA system for the entire process plant are available.

Cut-off features and controls Cut-off is designed with full automatic setting of all components that require adjustment for a different tube size, like entry guide and tube support rolls. A special software permits the optimising of cutting parameters and storage of the recipes for the various products for a quick and effective production order change. The mechanical parts, such as entry guides, are designed to avoid stoppage of the welding mill at the start up of new tube production. Thecontrollingsoftware isavailablewithdifferent configurations to minimise scraps at the beginning and end of production, at butt weld or “open seam” and after an unplanned mill stop. Mill setting system Depending on the model and size of mill, different systems are available for a repeatable roll setting up to the fully automated roll setting and management of production recipes typical of 8" mill and larger size. All the stands including turksheads are provided with absolute position transducers or encoders for setting the rolls according to type and size of tube being produced.

In line material/process controls Ultrasonic control of strip is undertaken at mill entry. The system includes a frame and a multitude of probes to inspect the strip at the entry of the mill. The inspection can be done on the whole width or on a percentage of it. Ultrasonic control of the weld seam and of inside scarfing is also checked. The weld inspection is carried out by using probe pairs and each probe inspects the weld with angle incidence for longitudinal defects. Depending on wall thickness, one or more probe pairs are sometimes necessary. The inner surface of the tube, where the burr has been removed with inside scarfing of the burr, shall be checked for conformity to requirements. This is usually done with an ultrasonic wall thickness measurement of the weld zone with oscillating probe movement. Other quality checks are normally carried out in the finishing area after hydro testing. Seam annealing and air cooling section Annealing of weld seam to either normalise the seam of HF welded pipe or to remove the un-tempered martensitic structure that remains in the weld seam is the most widely used method in particular for an API tube mill. Once the weld seam has been heated and kept at the annealing temperature for the required “soak time” it is then cooled down in the air. The section with rolls to support the tube for the air cooling section is not only extremely important to guide and support the tube during steady production, but the design configuration, together with the repeatability and precision of roll setting into the rest of the mill stands, plays a strategic role during the transitory period of starting a new product after roll changeover to minimise the amount of scrap. In fact, once the new tube head protrudes downstream of the last annealing inductor it is possible to start welding and annealing at a stable sustained speed while the head of the tube travels along the air cooling section into the emulsion cooling, into the sizing and through the cut-off without stoppages. OD laser measuring system At the exit end of the sizing and straightening mill an OD laser measurement system measures the actual tube diameter. The system, developed by OTO, measures the diameter around 360° and provides deviation from circularity in terms of ovalisation and actual diameter. All the data is displayed on a screen and the measurements can be statistically evaluated, saved and stored into a dedicated database with production of all required charts. The system, associated to the automatic

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September 2013