Sandblasting machine is mainly used to clean the surface of parts. Generally, the surface of parts has oil, oxide skin, rust, etc., so we need to use sandblasting machine to clean. While we are carrying out the derusting of parts, we often have the situation that the treatment is not in place, which can not achieve the expected effect. In fact, the main reason is that we have not done a good job in the control of sandblasting machine derusting, so in order to do a good job in the derusting of parts, today Shanghai sandblasting machine will share with you how to effectively control the derusting of sandblasting machine.
1. Early control
Before sandblasting, according to the provisions of rust grades and derusting grades of steel surfaces before painting, the rust grades of metal structure base surfaces 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 and derusting shall be hard, angular, dry (moisture content < 2%), free of soil and other impurities; quartz sand is better, coarse river sand can also be considered at the same time, sand transportation conditions, unit price, recovery capacity and other factors shall be taken into account; sand particle size shall be 0.5-1.5mm, and it shall be dried before screening, and stored in shed and indoor, and the mesh size shall be: coarse screen 40-48 holes / cm2 (particle size 1.2mm), 372-476 holes / cm2 (0.3mm)
After the rust removal plan is determined, the abrasives can be river sand, quartz sand or a mixture of the two. In the reinforcement of Gangnan Reservoir, through the comparison of pre spraying, the best effect is to mix quartz sand and river sand at the ratio of 1:1.
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 temperature of metal surface on the construction site must be inspected daily and construction records shall be made. When the relative humidity of air is greater than 85% and the metal surface temperature is lower than 3 ℃ above, 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.
The parts that cannot be sprayed by the spray gun shall be derusted by hand or power tools.