Question 475Steam Plants - Assistant Engineer

The correct answer is A) limit controls. Limit controls are safety devices that are interlocked with the burner circuit to prevent start-up and initiate a safety shutdown in the event of unsafe firing conditions in a large automatic auxiliary boiler. These limit controls, such as high pressure, high temperature, and low water level switches, are designed to interrupt the burner circuit and shut down the boiler before dangerous conditions can develop. The other options are incorrect because: B) Flame safeguard controls monitor the presence of a flame, but do not necessarily prevent start-up under unsafe conditions. C) Combustion controls regulate the air-fuel ratio, but do not directly shut down the boiler. D) Programming controls are related to the automated sequencing of the boiler, but do not specifically address safety interlocks.