What we often do with sandblasting machine is to clean the oxide skin and rust on the surface of workpiece, which is not only very fast, but also very clean. However, the price of a sandblasting machine is not cheap, so in order to cost, we need to extend the life of the sandblasting machine. So how to effectively extend the service life of sandblasting machine? First of all, the following six points must be done well:
1. Early control
Before sandblasting, the rust grade of metal structure base surface shall be evaluated. Check carefully, remove the welding slag, spatter and other attachments, clean the surface grease and soluble dirt, and properly handle the useless welding body or joint.
2. Abrasive control
Sand for sand blasting shall be hard, angular, dry (moisture content < 2%), free of mud and other impurities; quartz sand is preferred, coarse river sand is also acceptable; meanwhile, Shanghai shot blasting machine manufacturer shall consider factors such as sand transportation conditions, unit price, recovery capacity, etc.; sand particle size shall be 0.5-1.5mm, which shall be dried before screening, stored in shed and indoor, and the mesh size shall be : coarse sieve 40-48 holes / cm2 (particle size 1.2 mm), fine sieve 372-476 holes / cm2 (particle size 0.3 mm). After the rust removal plan is determined, the abrasives can be river sand, quartz sand or a mixture of the two.
3. Tool control
During sand blasting operation, the air pressure of air compressor is 6.0 × 105 ～ 6.5 × 105Pa, and the air pressure variation is 0.5 × 105 ～ 1.0 × 105Pa. Generally, the air pressure of sand barrel is 4.5 × 105 ～ 5.5 × 105Pa, which shall not be less than 4.0 × 105Pa. Before sandblasting, check whether the manufacturer of pressure vessel has the production license issued by relevant departments, whether the protective tools, safety belt (rope) and oxygen supply device worn by sandblasting workers are safe and reliable, and whether the nozzle is worn. When the orifice diameter increases by 25%, replace the nozzle.
4. Environmental control
Since sand blasting of hydraulic metal structure is an open-air operation, in addition to dust prevention and environmental protection, the environmental temperature, humidity and metal surface temperature of the construction site must be inspected daily, the dew point of the day shall be calculated, and construction records shall be made. When the relative humidity of the air is greater than 85% and the temperature of the metal surface is lower than 3 ℃ above the dew point, the construction shall not be carried out.
5. Process control
Compressed air for sandblasting must be treated by cooling device and oil-water separator to ensure dryness and oil-free; oil-water separator must be cleaned regularly. The distance between the nozzle and the surface of the base steel should be 100-300 mm, and the non sandblasted parts should be covered before sandblasting. The angle between the spray direction and the surface normal of the base steel is 15 ° - 30 °. After sand blasting and rust removal, before the next process, in case of rain or other conditions that cause the surface of the base steel to be wet, after the environment meets the construction conditions, dry the surface water with dry compressed air before construction. If sand blasting is necessary again, the abrasive requirements shall not be reduced to avoid reducing the roughness. During sandblasting, the nozzle shall not stay in a place for a long time. During sandblasting, sporadic operation shall be avoided, but the area of one-time spraying shall not be too large. The time interval between coating or thermal spraying process and surface pretreatment process shall be considered. Manual or power tools shall be used for derusting the parts that cannot be sprayed by sandblasting.
6. Quality control
After the completion of sandblasting, the rust removal parts shall be comprehensively inspected first, and then the cleanliness and roughness of the base steel surface shall be inspected. Focus on the parts that are not easy to spray, and reduce the requirements for rust removal by hand or power tools. When checking the cleanliness and roughness of the surface of the base steel, it is forbidden to touch it by hand; secondly, it should be carried out under the condition of good scattered sunlight or artificial lighting with the same illuminance to avoid missing inspection.