Why are naval boilers laid-up when idle for more than 24 hours?

Naval boilers are laid-up when idle for more than 24 hours primarily to prevent oxygen corrosion. When a boiler sits idle, the water inside can become stagnant, leading to an increase in the presence of dissolved oxygen, which can cause pitting and general corrosion of the metal surfaces. By laying up the boiler, specific procedures are followed to eliminate or minimize the water and oxygen presence, thereby ensuring that the integrity of the boiler is preserved when it is not in use.

While preventing scaling, improving efficiency, and reducing maintenance costs are important considerations in boiler operations, they are secondary concerns compared to the immediate risks posed by oxygen corrosion during extended periods of inactivity. Effective lay-up procedures involve the use of chemicals that scavenge oxygen and may include purging the system with inert gases to displace oxygen, thus safeguarding the boiler's materials against corrosion.