Compared with traditional insulating materials, epoxy vacuum casting products have many common advantages: no or few air gaps, and excellent electrical insulation performance of the products. The casting molding has good fluidity, naturally fills the cavity, and the uniformity of the products is good. Due to its excellent electrical performance, the product can be miniaturized and the structure of the main unit can be optimized. The product can be made into random shapes and formed in one go. The integrity of the metal inserts and insulating materials is good. It has good weather resistance and can be applied in both indoor and outdoor fields. The product is solid, flame-retardant and safe and convenient to use.
However, this process also has its drawbacks: there are no reinforcing materials in the system, the mechanical properties are poor, and there are cases of breakage during the operation of the main unit. Certain stress is generated within the product. When the accumulated stress is released, there is a risk of cracking in the product. There are various defects in the appearance quality.
At present, two types of resins widely used in vacuum oil injection equipment for transformers in China are epoxy resin and unsaturated resin. Unsaturated resin is inexpensive, can be cured at room temperature, and has a simple casting process. However, it has low electrical and mechanical strength and poor heat resistance.
In addition, the saturated vapor pressure of unsaturated resin is high, and the mixed adhesive should not be vacuum degassed. Vacuuming is also not advisable during casting, as there are bubbles in the casting body. The curing shrinkage rate of unsaturated resin is large, and the mixed adhesive is prone to cracking during curing.
Therefore, unsaturated resin is only suitable for products with low voltage. The curing shrinkage rate of epoxy resin is small, and the full vapor pressure is low. It is suitable for casting under high temperature and high vacuum conditions, which makes the fluidity of the mixed adhesive better and then obtains the casting body with the desired function.
When repairing, several key steps should be noted: disassembly, cleaning, inspection and installation. It is very important that vacuum equipment, regardless of its size, belongs to mechanical equipment. When disassembling, follow the principle of handling with care. Do not act rashly. Under no circumstances should a sledgehammer be used to strike. When cleaning parts, be thorough and clean to facilitate the identification of problems and risks.
Vacuum pump products are quite different from general mechanical products. General mechanical products often have beveled edges and corners, while the edges and corners of vacuum pumps are clear and can easily hurt hands. Extra care should be taken and this should be kept in mind. Inspection is a meticulous job. No detail should be overlooked, and there must be no mentality of taking chances.
There was a piece of equipment that the user had stored for four years. After completing the routine sorting work, the user stuck to the old ways and connected the pipelines to start vacuuming. However, it still couldn't meet the factory standards. Everything was checked, but the vacuum rubber hose for gas supply was not inspected. At that time, the user thought that the vacuum rubber hose would not leak.