Which of the following is a type of mechanical carryover in a boiler?

Mechanical carryover in a boiler occurs when water is carried into the steam lines along with steam, leading to potential issues such as reduced efficiency and equipment damage. Priming, which is the correct choice, is a phenomenon where water is carried over with the steam due to sudden changes in operating conditions, like rapid increases in firing rate. When the firing rate of a boiler increases suddenly, it can create turbulence and agitation in the steam drum, resulting in a significant amount of water being entrained in the steam, hence causing priming.

Foaming due to chemical reactions leads to a different type of water carrying issue, as it primarily pertains to the formation of bubbles in the boiler water that can cause erratic water levels, but it does not inherently focus on the mechanical carryover aspect.

Excessive steam drum size does not directly cause mechanical carryover. In fact, an adequately sized steam drum may help mitigate carryover by allowing for more separation of steam and water.

Reaction with oxygen scavengers addresses water chemistry and treatment, aimed at preventing corrosion and scaling rather than focusing on the mechanical aspects related to carryover in steam generation.

Thus, the option highlighting priming due to sudden firing rate increases accurately reflects a typical scenario where mechanical carryover arises in boiler