Which of the following components is critical for the operation of a watertube boiler?

The steam drum plays a vital role in the operation of a watertube boiler. Essentially, it serves as a reservoir for water and steam, ensuring that there is a consistent supply of steam to meet the demand of the system. In a watertube boiler, water circulates through tubes that are heated by combustion gases, and the steam drum collects the steam produced from this process.

The steam drum also facilitates the separation of steam from water, allowing for the differentiation of steam quality and ensuring that only high-quality steam exits the boiler to be used in the process or systems it serves. Therefore, this component is critical not only for providing steam but also for maintaining system pressure and temperature.

While other components like the combustion chamber, heat exchanger, and pressure relief valve are important for the overall functioning and safety of a boiler system, the steam drum specifically stands out as essential in the context of a watertube boiler's operation.