Boiler water supply requirements and precautions

Steam is produced by heating water, which is one of the essential parts of a steam boiler. However, when filling the boiler with water, there are certain requirements for water and some precautions. Today, let us talk about the requirements and precautions for boiler water supply.

There are generally three ways to fill the boiler with water:
1. Start the water supply pump to inject water;
2. Deaerator static pressure water inlet;
3. Water enters the water pump;

Boiler water includes the following requirements:
1. Water quality requirements: must meet water supply standards;
2. Water temperature requirements: The supply water temperature is between 20℃~70℃;
3. Water loading time: no less than 2 hours in summer and no less than 4 hours in winter;
4. The water supply speed should be uniform and slow, and the temperature of the upper and lower walls of the drum should be controlled to ≤40°C, and the temperature difference between the feed water temperature and the drum wall should be ≤40°C;
5. After seeing the water level in the steam drum, check the operation of the electric contact water level gauge in the main control room, and make an accurate comparison with the reading of the two-color water level gauge. The water level of the two-color water level gauge is clearly visible;
6. According to the site conditions or the requirements of the duty leader: put in the heating device at the bottom of the boiler.

Reasons for the specified time and temperature of boiler water:
The boiler operation regulations have clear regulations on the water supply temperature and water supply time, which mainly considers the safety of the steam drum.

When the cold furnace is filled with water, the drum wall temperature is equal to the surrounding air temperature. When the feed water enters the drum through the economizer, the temperature of the inner wall of the drum rises rapidly, while the temperature of the outer wall rises slowly as heat is transferred from the inner wall to the outer wall. . Since the drum wall is thicker (45~50mm for medium pressure furnace and 90~100mm for high pressure furnace), the temperature of the outer wall rises slowly. A high temperature on the inner wall of the drum will tend to expand, while a low temperature on the outer wall will prevent the inner wall of the drum from expanding. The inner wall of the steam drum generates compressive stress, while the outer wall bears tensile stress, so that the steam drum generates thermal stress. The size of the thermal stress is determined by the temperature difference between the inner and outer walls and the thickness of the drum wall, and the temperature difference between the inner and outer walls is determined by the temperature and speed of the supply water. If the water supply temperature is high and the water supply speed is fast, the thermal stress will be large; on the contrary, the thermal stress will be small. It is allowed as long as the thermal stress is not greater than a certain value.

Therefore, the temperature and speed of the water supply must be specified to ensure the safety of the steam drum. Under the same conditions, the higher the boiler pressure, the thicker the drum wall, and the greater the thermal stress generated. Therefore, the higher the boiler pressure, the longer the water supply time is.