In the medical field, "lost" tubes are tubes which have to be replaced after single use. This is not genuine tube cleaning in the proper sense and is very often applied in the medical sector, for instance with cannulas of syringes, infusion needles or medical appliances, such as kidney machines at dialysis. The reasons for the single use are primarily the elimination of infection risks but also the fact that cleaning would be very expensive and, particularly with cheap mass products, out of all proportion in terms of cost. Single use is therefore common practice with tubes of up to 20 mm diameter. For the same reasons as in the medical sector, single use may also be applicable in the food and pharmaceutical process technology, however in these sectors the tube diameters may exceed 20 mm.
In other fields (e.g., in heat exchangers), tubing may also sometimes need to be replaced (or removed, plugged, etc.), but this typically occurs only after a prolonged use, when the tube develops serious flaws (e.g., due to corrosion).