Drain, block steam, and exhaust air, therefore, in steam systems, drain valves are very important as they can maximize the utilization of heat energy and are the most important link between steam and condensate systems.
1. The essence of steam is water, which is a gaseous water containing a lot of heat. In the production process of using steam, when steam passes through heat exchange equipment, the heat exchanger absorbs the latent heat of the steam and converts it into heat energy on the product. At this time, the steam loses its latent heat and condenses to form condensate. However, condensate does not have the ability to quickly heat objects like steam, so it must be quickly discharged. Otherwise, condensate is blocked in the equipment, steam cannot enter, heat exchange efficiency is greatly reduced, and the product cannot be heated. Moreover, condensate will corrode the heat exchange equipment. Therefore, it is necessary to quickly drain the condensate through a drain valve.
2. During the transportation of steam, due to the low ambient temperature, it will radiate and lose some heat, and also produce a small amount of condensate. Therefore, it is necessary to install a drain valve to make the steam as dry as possible when it reaches the steam consumption point, avoid water hammer and corrosion, and make the steam more economically and effectively utilized.

3. The initial air in the pipeline and some hot air during operation during start-up can greatly reduce the heat transfer efficiency of steam, and may also cause "air binding", which prevents the heating of the product. Therefore, it is necessary to automatically discharge air through a drain valve.

In practical operation, we have seen some users who did not install a drain valve, or because the original drain valve often leaked air or was often blocked, they later dismantled the drain valve and replaced it with a regular globe valve or ball valve, and regularly sent people to manually drain it; some used solenoid valves or pneumatic shut-off valves, and timed automatic drainage with relays; some directly connected the condensate water to the public recovery tank and pumped it back to the boiler room; some used needle hole drain valves; all of these, users thought that the problem was solved without the previous problems of the drain valve, but little did they know that this would cause serious steam waste and many other problems. The analysis is as follows:
1. To achieve the discharge of condensate water, manually adjust the opening of the valve.
In theory, this is possible, however, it is only suitable for laboratory research and is only an ideal state, as the conditions and operating conditions that need to be achieved are extremely extreme. Therefore, in practical operation, it is not a practical solution.
The biggest problem is how to set the opening of the valve. If it is set to a fixed opening, it cannot be adjusted according to the speed of condensate formation. In fact, the amount and speed of condensate formation in the same system are not fixed. For equipment, the amount of cold condensate during startup and the amount of condensate during normal operation are very different, and fluctuations in product load during operation can also affect the amount of condensate. Similarly, during steam transportation, the amount of condensate is also related to outdoor temperature and weather factors.
If the valve opening is increased, steam will leak. If the opening is reduced, the product will heat up slowly. Therefore, these valves cannot be used as substitutes for drain valves.
2. Directly connect the condensate water to the public recycling tank
This method is even more unacceptable! On the surface, it seems to be completely enclosed for recycling without any waste. However, in reality, after steam leaks into the condensate recovery tank, it will gradually condense, losing its latent heat in vain. However, latent heat accounts for 70% of the total heat of steam, so it is necessary to use a drain valve to prevent steam from being trapped in the equipment.
In summary, a thermal energy system must use a drain valve. As long as the drain valve is selected properly and its characteristics and application are consistent, it will work efficiently. Therefore, selecting the correct drain valve is an important task for every thermal energy engineer.