What function does the surface blow pipe in the steam drum serve?

The surface blow pipe in the steam drum plays a crucial role in maintaining the quality of steam produced by the boiler. Its primary function is to prevent the accumulation of scum and foam, which can form on the surface of the water inside the steam drum. When water is heated to generate steam, impurities can rise to the surface, and if not properly managed, these impurities can carry over with the steam, resulting in wet steam that may cause operational issues in turbines and downstream equipment.

By directing a stream of water and contaminants away from the surface, the surface blow pipe effectively removes these undesirable materials, ensuring a cleaner steam output. This action is essential for maintaining the efficiency of the boiler system, protecting equipment integrity, and improving overall performance.

The other options focus on functions that do not pertain to the role of the surface blow pipe. For instance, carrying steam from the boiler, increasing steam pressure, or lowering the boiler temperature are functions associated with other components within the boiler system, but not specifically attributed to the surface blow pipe.