What are the regulations on the time and temperature of water supply before the boiler starts? Why?

The water inlet speed before the boiler is started should not be too fast, generally not less than 4h in winter, 2～3h in other seasons, especially at the initial stage of water inlet. The inlet water temperature of the cold boiler is generally 50-90°C, so that the difference between the temperature of the feed water entering the drum and the temperature of the drum wall is not more than 40°C. For boilers that are not completely cooled, the inlet water temperature can be compared with the drum wall temperature. Generally, the difference should be controlled within 40°C, otherwise the inlet water speed should be slowed down. The reason is:

(1) Because the wall of the steam drum is thicker, the expansion is slow, while the wall of the tube connected to the wall of the steam drum is thinner and the expansion is faster. If the water inlet temperature is too high or the water inlet speed is too fast, it will cause uneven expansion, cracks in the weld, and damage to the equipment.

(2) When the feed water enters the steam drum, it always contacts the lower half wall of the steam drum first. A large difference in expansion will cause a large additional stress to the steam drum, causing the steam drum to deform and cracks in severe cases.