2017-04-24 16:40:53   From:   Click:

NEW SHIPBUILDING: PRE-DRYING, BLASTING, PAINTING AND DRYINGIn shipyard preservation lines, sheets and profiles are t
NEW SHIPBUILDING: PRE-DRYING, BLASTING, PAINTING AND DRYING In shipyard preservation lines, sheets and profiles are thoroughly blast cleaned and provided with a temporary corrosion protection coating. Along with the external transport unit, a preservation line consists of a pre-heating oven, a pass-through blasting machine, a painting unit and a drying tunnel with its associated slat conveyor. Typical plate widths can vary from 800mm to 4m with process line speeds between 0.5m/min to 3.0m/min. The abrasive streams remove scale, rust and other deposits from the surface. After blasting, the sheets are cleaned to remove dust. In the painting unit the components are automatically coated with Shop Primer. Then the sheets and profiles are moved on the slat conveyor through the drying oven. Conveyors then automatically carry the protected plates and profiles to subsequent processes such as flame or laser cutting, welding, etc. MARKING AND EDGE BLASTING After the material is painted and dried it is identified with an internal production number in the marking station so that it can be traced in later treatment processes. Before welding the cut sections are passed through an edge-cleaning unit. Both techniques ? wheel blasting and air blasting ? are suitable for this edge blasting process. OPEN BLASTING OF SHIP SECTIONS Pre-fabricated ship sections are selectively blasted in large blast rooms or halls. Typically four to eight blast operators are working in these facilities. Carefully specified dust collectors ventilate the dust from the hall. The ventilation is additionally provided with air de-humidifiers which keep the relative humidity below 60% in order to avoid any premature corrosion of the bare steel. The spent abrasive is returned to the system by mechanical or pneumatic recovery systems. Using air washing and screening processes, debris, dust and fines are removed. A wide range of pressure vessels for single or multiple operator use is available. PAINTING AND DRYING OF MARINE SECTIONS After blasting the sections must be painted. Depending on the required coating thickness, the ship sections are painted with three to five coats. In order to avoid disturbance by the weather, the sections are processed in large painting halls where typically four to eight painters work simultaneously. Similar to blasting, 50% to 70% of the painting work is carried out inside the sections. Local ventilation within the sections is performed by grounded hoses for removing dust and solvent vapours. 1-C pumps as well as 2-C mixing and dosing units can be used. A unique special fresh and exhaust air system has been developed to minimise operational costs. After the painting process the facility can be switched over to the drying process.

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