Ⅰ.Failure Analysis:

1. This equipment is the key equipment of the enterprise, it has a great impact on the production after the shutdown, because the interface of the pre-cooler has been cracked twice before, and after the two welding, the surface has been oxidized seriously and can not be repaired by welding again, so we had to replace the precooler. But if we do not take measures, the new purchase of pre-cooler still has the possibility of vibration crack, one vibration crack, cause R404A refrigerant leakage, because this refrigerant is the most advanced environmental protection refrigerant, the price is expensive. In order to ensure that the newly-purchased precooler is not cracked and can operate normally for a long time, it is decided to improve the technology of the newly-purchased precooler, re-weld and reinforce it so that the port has no obvious vibration.

2. Disassemble the cooling fan of the compressor and analyze the reason. It is found that the motor does not have ball bearing, but uses the shell bearing. Because the shell has been deformed during the long-time high-temperature operation, the shaft of the fan swings back and forth during the rotation of the fan and forms the dead point, shell bearing is a one-time products, can not be repaired, can only be replaced. After contact with our technical engineers, the fan for Mexico production support, purchase cycle can not be determined, expensive. Therefore, it was decided to use a domestic fan instead, but the voltage of this fan is 220v single-phase, and the domestic 220V Fan with the same power and the same volume can not be found, and the volume of the same power is very large and can not be directly replaced, finally, a three-phase 380V FAN is found. The parameters can meet the needs, but the original control circuit can not meet the needs.

II. Implementation Plan

1. Surfacing reinforcement. Newly purchased pre-cooling, the air inlet end of the device is formed by high temperature automatic welding, the welding layer is thin, not strong enough, installed in the vibration of larger equipment easy to crack. This time, the silver electrode surfacing technology was adopted to reinforce the welding spot, and the thickness of the welding layer was 3 times, the ability of anti-cracking was improved greatly.

2. Port reinforcement. In order to make the welded end more solid, the precooler Shell and compressor exhaust pipe in the position of the weld installation of shock-resistant stiffeners 4, into a cross-symmetrical type. In this way, in addition to the thickening of the welding another anti-vibration displacement measures.

3. Add cushioning. The old way to fix the precooler is to hold it in place. The port of the precooler vibrates greatly with the base of the equipment. There is no cushion for the vibration, and it easily resonates with the exhaust pipe of the compressor. When repair, add buffer rubber pad under the two fixed holding cards of the original precooler, so that even if the exhaust pipe vibration, precooler has a certain cushion margin, thereby reducing the shock to the pipe mouth.

4. Reinforced tooling. If the vibration intensity of the exhaust pipe is not reduced, there will still be a large impact vibration on the inlet of the precooler. So in the compressor exhaust end and the precooler pipe end between the installation of anti-vibration fixed tooling. Through on-site research, two sets of fixed tools were installed at the base and the box column to reduce the vibration intensity of the compressor exhaust pipe and the impact on the precooler pipe end.

5. Fan and compressor synchronous work, first draw the modified drawings, repeated analysis of the feasibility.

Ⅲ.Conclusion

Since the retrofit was completed in November 2015, there is no obvious vibration at the pipe end of the precooler, and the fan works normally after installation. It provides a guarantee for the normal work of the high and low temperature humid heat test box, and also saves a lot of maintenance and cost for the company. Moreover, there are several such ring measuring devices and several compressor cooling fans. This transformation has provided a good solution for the subsequent replacement of cooling fans. So far, the electronics manufacturer replaced 4 cooling fans.