Anti-freezing of compressed air pipelines
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It’s hilarious – compressed air pipelines actually have insulation to prevent freezing. It has good insulation and is resistant to freezing; yet there’s not even heat tracing – what’s the use of an insulated pipe then?
Yes, having insulation without heat tracing really doesn’t work. Since compressed air does not pass through a dehumidifier, it theoretically contains trace amounts of water. I encountered this issue when I first started working; the solution was to regularly open it and drain out the water. In our factory, compressed air now passes through a dryer; it is part of the same system as the instrument air. Theoretically, there should be no water present, and at present checks are only carried out once before winter arrives.
Our compressed air and instrument air are separated; the compressed air contains a lot of water. Last year, an 89mm pipe got frozen solid, and we spent the entire day dealing with that issue :( (:' (:'
If it is a high-temperature exhaust pipeline of an air compressor, and calculations have confirmed that no condensation water forms along the pipeline, simply providing insulation is sufficient. However, the transportation of compressed air in a saturated state, especially during winter operations in cold regions, requires either transporting it after overheating or providing heat tracing.
When winter comes, the problem of cleaning air and water here becomes severe, and the control valves fail frequently. I have increased the efforts to clean the air and water, and I operate the control valves at appropriate times. We have now added a drying dehydrator, but it does not provide insulation. The effect is still not very good; the control valve often malfunctions.
Using a muscle-building dryer is better than relying on insulation; it requires less investment, is easy to manage, involves less work, and its effectiveness is easier to verify. With insulation, one also has to consider issues such as its insulating performance. Moreover, these days, compressed air and instrument air are both made from gas of the same quality, with oil and water removed, so the investment required isn’t high
Dryers are the preferred option, followed by enhanced dehydration. . .
It can be sent along with the return water from the circulating system.
Whether the compressed air pipeline needs insulation or anti-freezing treatment depends on the dew point; at -40°C, anti-freezing measures are probably not necessary. Even for freeze protection, some people leave the valves slightly open at the ends to maintain flow and prevent freezing
If it is unpurified air, it generally does not pass through a dryer for drying, so it will certainly contain trace amounts of water. If the temperatures are low in winter, the unpurified air may freeze during transmission within the system, gradually leading to localized freezing and blockages; we have encountered this situation as well. To ensure normal operation of the production process, insulation can also be considered
Whether to adopt anti-freezing measures should be determined based on the local extreme minimum temperatures and the dew point of the compressed air pressure. As for what type of anti-freezing measure to use – insulation or heat tracing – it needs to be decided in light of the local weather conditions, as well as the temperature of the compressed air, the distance of transmission, and the way in which it is used.