High quality of surface preparation and interoperation metal-roll protection are the top priorities for protective coating longest service life and quality. This preparation can be made by shot blasting with further metal-roll coating with electrically conductive protective primer at the stage of release for manufacture. After metal structure assembly the product needs degreasing and weld seams protection. This effectively reduces product preparation time before final painting.
The standard configuration of metal-roll shot blasting and preservation line manufactured by Techvagonmash includes the following equipment:
- Loading rack,
- Conveyor system,
- Preliminary drying and heating chamber,
- Shot blasting chamber,
- Painting booth,
- Drying chamber,
- Receiving rack.
The line can be supplemented with blasting chamber for water (ice, snow) and dirt removal at the request of the customer.
1. Loading rack
2. Conveyor system
3. Preliminary drying and heating chamber
4. Shot blasting chamber
5. Painting booth
6. Drying chamber
7. Receiving rack
Preliminary drying and heating chamber
Going through preliminary drying and heating chamber (with inside temperature set at 250 С) the metal roll is dried from moisture and oil fractions and heated to 35-40 С. The surface free from moisture prevents the blasting media adhesion inside the chamber and preliminary heating helps more effective metal roll surface cleaning. Besides, this temperature improves the painting quality and significantly reduces further drying time. The drying becomes more effective due to forced air convection. Part of heated circular air goes through connection duct to the final drying chamber for its heating if heat is needed. Natural gas, diesel fuel, electric power or overheated steam can be used as energy carrier.
Shot blasting machines
After preliminary welding the metal roll is transferred to shot-blasting chamber by transfer table. At the entry to the shot-blasting chamber there is a sensor, determining the metal roll height and giving a signal for up/down travel of blasting media sweeping brush. The shot blasting chamber provides the 2nd grade of product cleaning according to SA 2.5 SIS 055900 from rust, calx, and other foreign matters from both sides. Depending on maximal dimensions of the processed metal roll, the shot blasting chamber can have from 4 to 8 shot blasters. The shot blasters are located at effective angle of surface from above and beyond the metal roll, which excludes the blind zones.
The internal space of the chamber is lined with wear-resistant manganese steel plates. The shot blasters are very important, their parts work under severe abrasive wear conditions. For this reason the shot blasters produced by Techvagonmash are made of high-strength materials, providing the long service life.
The blast media removal from the metal roll surface is a very important condition. The surface cleaning with brush and compressed air is provided.
After shot blasting the metal roll goes to painting booth.
To minimize the paint overrun the painting booth is fitted with a system of sensors, identifying the width and height of painted product and applies a primer precisely on a product. The painting equipment provides the coating thickness 15-20 micron.
To avoid the raw paint damage the metal roll is transferred by the chain conveyor with bearing elements. It provides minimal contact with painted surface. The paint that couldn’t reach the product is taken with air flow and directed to labyrinth filters, installed on air ducts side channels. The filtered exhaust air is emitted to the atmosphere.
The primer drying chamber works in recycling mode: the heated air is fed from the preliminary drying chamber with 10-15% fresh air intake from “outdoors” to prevent the recycling air oversaturation with solvents. The temperature from 30 С to 80 С is set according from primer type. As well as in painting booth, the transportation is made by chain conveyor with bearing elements. It guarantees minimal contact of painted surface with conveyor surface, protecting the painted surface from damage. The line is fitted with special filters, providing 92-98 % filtering of discharged air.
Techvagonmash offers various automated lines for sheet and section metal roll. To increase the operation efficiency these lines are customized according to workshop environment of the customer. In recent years Techvagonamsh has designed and delivered about 10 lines for different customers, working in various industries (shipbuilding, railway cars building, bridge and construction metal structures).