The refrigeration equipment is not working well, have you paid attention to the welding problem?

The refrigeration equipment is not working well, have you paid attention to the welding problem?

1. What are the effects of poor welding?

Firstly, welding problem: Poor welding may result in leakage points

The original function of welding is to connect the refrigeration equipment, so as to connect the internal and external units, forming a closed system. The refrigerant can circulate inside the internal and external units. Generally, the large pipe runs gaseous refrigerant, while the small pipe runs liquid refrigerant. What is the use of refrigerant?

Refrigerant, also known as refrigerant, refrigerant, or snow seed, is a medium substance that completes energy conversion in refrigeration systems. Simply put, it means absorbing heat at the indoor unit, releasing heat at the outdoor unit, and transporting indoor heat to the outside through it. If the welding of the refrigeration system is not good, the refrigeration equipment will leak, and over time, not only will there be no refrigeration effect, but it is also more likely to damage the refrigeration compressor.

Secondly, welding problem: oxide layer is generated inside the copper tube

As shown in the left figure below, there was no standardized operation during the welding process, which resulted in the formation of black oxide skin on the inner wall of the copper tube. However, in the right figure below, proper operation was performed, and the copper tube at the welding point was as bright as new, mainly due to the absence of oxide skin inside the tube.

It should be understood that if oxide skin deposits on the side of the indoor unit, the refrigerant flow rate of the indoor unit will be greatly affected, and the refrigeration effect may not be as expected as a result. If oxide skin enters the compressor, it will increase compressor wear (reduce service life), and even directly lead to compressor damage.

No matter what kind of after-sales problems arise, it takes a lot of time and effort. Therefore, we should avoid such situations when installing and constructing refrigeration systems.

2. How to avoid welding hazards?

Firstly, the operation of nitrogen filling welding

How to prevent the generation of oxide skin inside copper pipes during welding? Just perform nitrogen filling welding! So why can nitrogen filled welding prevent the formation of oxide scale?

Due to the stable chemical properties of nitrogen, nitrogen filled welding can prevent the formation of oxide scale on the inner wall of copper pipes at high temperatures. And the air contains oxygen, which will undergo oxidation reaction when welding copper pipes, producing oxides.

It should be noted that after welding is completed, nitrogen gas should be added for another 3 to 5 minutes until oxidation no longer occurs. It is strictly prohibited to cool the surface of copper pipes with cold water. In addition, it is emphasized that the nitrogen filling protective gas must be nitrogen, and the use of oxygen is prohibited to avoid the risk of explosion! During welding, the nitrogen pressure should be controlled between 0.2-0.3kgf/cm ² Left and right, not too large.

Secondly, airtightness testing

After nitrogen filling welding is completed, it does not necessarily mean that the welding is complete. If there are sand holes, bubbles, etc. during welding, it is necessary to re weld. Because airtightness testing is required. After the welding is completed, a pressure test must be carried out on the copper pipe. A certain pressure of nitrogen gas is filled into the copper pipe to maintain pressure, and nitrogen gas is slowly injected from the low-pressure process port. If there is a liquid circuit in the system, the solenoid valve should be energized and opened first. A positive pressure gauge should be hung at the high-pressure process port to test the pressure.

R410A refrigerant needs to maintain a pipe pressure of 40 kilograms, while R22 refrigerant needs to maintain a pipe pressure of 20 kilograms. The holding time is 24 hours. The change in ambient temperature can cause a change in nitrogen pressure. For every ± 1 ℃ temperature difference in the ambient temperature, there will be a pressure difference of ± 0.1 kgf/cm2.

Attention: It is strictly prohibited to use oxygen for pressure maintenance. Oxygen in contact with the refrigeration oil in the refrigeration system can easily cause explosions!

3. Summary

Welding is a crucial step in the installation and construction process of refrigeration equipment. Improper welding may lead to leakage points at the welding site; During the welding process, oxide skin is generated inside the copper tube. The best way to prevent internal oxidation of copper pipes during the welding process is through nitrogen filling welding; It is necessary to conduct a pressure test to ensure that there are no leakage points at the welding site.