Traditional dry blasting has many drawbacks. For example, sand grains hit the metal surface at high speed during processing, which is easy to break and produce a large amount of dust, which is harmful to workers' health. A large amount of dust is generated during construction, causing environmental pollution. Since a large amount of sand is eliminated as dust, the abrasive consumption is large and the cost is high. Therefore, the dry processing method that has been used for nearly a century has been unable to meet the requirements of modern technology development and civilized production.
I, the type of wet sandblasting equipment
Wet blasting has established itself in the field of industrial surface treatment. There are several different ways of this technology:
The first type is to add high-pressure water to the nozzle of the standard dry blasting equipment. This type of equipment is not produced by normal manufacturers. It is basically a home-made equipment. This kind of equipment can reduce dust to some extent, but there are also The following disadvantages:
1. When the sand convoy is unstable, the dust suppression effect is not good. Comparing with dry sandblasting, the amount of sand consumption does not change, but the water consumption is increased.
2, about one ton of water per hour, in the case of limited construction sites, dirty water cross-flow, causing secondary pollution.
3, recycling of used-sand is more difficult; Also drying and sieving will inflict a lot of labor costs.
4, It causes a collateral rust because the amount of water makes adding rust inhibitor too expensive.
The second type of high-pressure cleaning machine is equipped with a suction pipe at the nozzle, also called siphon sand wet sandblasting. The processing speed of this kind of equipment is not slow. Disadvantages of such equipment:
1, the water consumption is large, or the problem of rust prevention cannot be solved.
2, the nozzle and the sand suction device wear fast, parts cost and maintenance cost are high.
3, the recoil force is too strong, not suitable for high-platform work; the operator is difficult to maintain stability when switching the handle.
4, Vital drawback that the siphon sand tube at the nozzle head cannot be too long, otherwise the sand cannot be fetched, which means that there must be a sand storage next to the operation. This problem has prevented many users to purchase this equipment because it can only be used on the ground.
The third type is the prior addition of water to the inner abrasive tank and the use of this mixture of abrasive and water throughout the process. Because this technology uses compressed air to spray a mixture of water and abrasive from the tank, we call it a true wet blasting technique. This technology reduces the amount of very fine dust formed in conventional dry blasting by 95%. The amount of abrasive mixed with water can be adjusted independently of the compressed air. A variety of blast cleaning work can be achieved with this type of machine.
Second, economic benefits
In terms of the cost of use, the patented wet blasting system has the following basic advantages: the abrasive does not have to be stored dry. At the same time, the amount of abrasive and water used in this method is less than 40% of the original amount, which is not only environmentally friendly but also more economical. Cost savings can be achieved with a dedicated dispensing valve that reduces the amount of waste generated by 50% without compromising performance. In dry blasting machines, the blast cleaning object has to be completely sealed and a suitable pumping device needs to be installed, while the patented wet blasting technology does not require time-consuming and costly external installation. Because the amount of dust is reduced by 95%. This type of machine can even be used in demanding locations such as narrow spaces, high-sensitivity technical equipment or open to public spaces.
Third, abrasive selection
In principle, all abrasives that are heavier than water can be used, such as corundum, cinder, stone, and abrasives based on glass, limestone or soda.
Fourth, the formation and prevention of floating rust
One of the most common arguments for sandblasting metal surfaces using wet blasting techniques is the formation of so-called rust. On the other hand, it is unknowingly known that rust can be prevented by using environmentally friendly inhibitors and using a single component polyurethane coating. Let's take a more detailed look at this issue.
Environmentally friendly inhibitors are manufactured on a water-based basis and are primarily used in anti-flash rust agents for waterborne coatings. These rust inhibitors help to bond the primer to the substrate, so there is no need to worry about the combination of rust inhibitor and paint. The problem of force is that the blast cleaning of the steel surface can reach the standard purity level of Sa 2.5. The formation of rust can be prevented or delayed within 48 hours by adding it directly to the gas stream with abrasive and water.
In addition, there is now a special single-component polyurethane topcoat that maintains a 99% surface moisture level, which permanently seals the surface. The manufacturer guarantees that no rust will occur within five years. This protection is generally achieved after a single coating, so there is no need for multi-layer coating and a longer warranty time than comparable products.
The extra cost of special coatings and inhibitors can be offset not only by the cost savings of abrasives but can even be further reduced. The rust inhibitor will incur a 6% additional cost. The rust inhibitor is used under the condition that the dry or wet surface has a standard purity grade of Sa 2-2.5.
Compared with wet and dry blasting technology, wet blasting obviously has a big advantage. Surface cleaning of metals with dry jets is common, but in most cases, there is greater environmental pollution. On the one hand, the dust problem causes all parts to be sealed and dusted. On the other hand, the injected waste usually needs to be treated as a hazardous substance. When removing old paint layers, there are usually heavy metals
Contaminated coatings, which can cause secondary pollution to the waste to be treated. True wet blasting technology does not have any expenditure on dry storage of abrasives, with a 60% reduction in consumables and 95% reduction in dust, and can be used in demanding environments without special cover. The environmentally friendly rust inhibitor and the one-component polyurethane coating allow blast cleaning on steel to achieve a standard purity level of Sa 2.5 and a 35% savings compared to dry blast cleaning.
With the increasingly strict environmental protection measures across the country, wet blasting will be more widely used in the future, especially in production sites with explosion-proof requirements. Vapor-grinding wet blasting is the most economical, safest and most efficient.