What is one characteristic of water tube boiler designs?

One characteristic of water tube boiler designs is the requirement for careful assembly in the field. Water tube boilers consist of many small tubes that carry water and steam, which need to be securely connected and assembled properly to ensure safe and efficient operation. The construction allows for higher pressures and temperatures, which means that precise manufacturing and assembly are crucial to prevent leaks and ensure structural integrity. This complexity often means that skilled technicians must carefully piece together the components during installation or maintenance.

The other options suggest characteristics that do not align with the complexities involved in water tube boiler designs. For instance, while simplicity in design might be found in certain fire tube boilers, water tube designs are typically more complex. Similarly, the need for skilled assembly extends to a consideration of maintenance; while maintenance can be lower in quantity compared to other systems with numerous similar parts, the intricacies of design necessitate expert handling rather than low maintenance due to fewer duplicates. Lastly, while some water tube boilers can be relatively compact, their installation and assembly requirements still demand careful attention and expertise, which does not solely focus on size.