(b) Regulating Feed Supply

The feed supply to the boiler is regulated by a level transmitter connected to the boiler drum. This transmitter measures the current water level and sends a signal to a controller. The controller compares this measured value to a pre-set value (the desired water level). The output from the controller, which uses a flapper and nozzle mechanism, is sent to one of two feed regulators: a 7k line regulator for low-demand operation and an 18k line regulator for high-demand operation.

• When the boiler is operating in low mode (7k), the 7k controller is active and the 18k controller is completely shut. In this mode, the economizer pumps are used.
• When the boiler is operating in high mode (18k), the 7k controller is shut and the 18k controller is regulating the flow. During this high-demand mode, the main feed pumps are used.

This system ensures that the correct amount of water is supplied based on the boiler's operational load, utilizing two separate feed lines and pumps to handle different capacities efficiently.

(c) Prevention of Oil Contamination

• Means are provided in the hotwell to prevent and handle oil contamination of the feed water. Since oil is less dense than water, it floats on the surface, where it can be observed through an observation window.
• A key feature for preventing contamination is a syphon arrangement that draws feed water from below the surface, ensuring that the uncontaminated water is passed to the hotwell and then to the boiler.
• Any oil floating on the surface can be blown down to an oily bilge tank through a scum drain valve. If oil contamination is detected, it is crucial to immediately examine and rectify the cause of the contamination before taking any other action.