What is the upper sheet in the boiler tube referred to as?

The upper sheet in the boiler tube is referred to as the wrapper. This terminology is used in the context of boiler construction, where the wrapper plays a crucial role in the overall integrity and design of the boiler. The wrapper sheet is the outer layer that encases the boiler tubes and provides structural support, while also helping to protect the tubes from external environmental factors.

In the context of boiler operation, understanding the components and terminology, like the wrapper, is vital for ensuring safe operation and maintenance of the boiler system. Proper nomenclature aids in effective communication among engineers and technicians, enhancing the understanding of boiler assembly and function.