Why should a boiler be warmed up slowly during startup?

Warming up a boiler slowly during startup is crucial to allow uniform expansion of the drums and tubes. When a boiler is heated, the metal components expand due to the increase in temperature. If the warming process is too rapid, it can lead to uneven thermal expansion. This uneven expansion can cause stress in the material, potentially leading to cracks, warping, or even catastrophic failure of the boiler structure.

By gradually increasing the temperature, all parts of the boiler—such as the drums, tubes, and associated fittings—can expand uniformly, minimizing the risk of thermal stress and damage. This approach not only enhances the longevity of the boiler but also improves overall safety during operation.

The other options, while related to boiler operation, do not address the critical aspect of uniform expansion as effectively. Increasing pressure gradually is important, but it is part of managing the system during operation rather than during the warming phase. Preventing noise is a secondary effect of proper startup procedures rather than a primary reason for slow warming. Quick ignition is a concern for operational efficiency but is not directly related to the initial warming up process.