pegging of deareator

ramendral1; Dear eater pigging out?

This question relates back to the function of the Deareator, why it exists and then how it works. The purpose of the deareator is to remove disolved gases from the feedwater to the boiler . . . the most important of which is oxygen.

Looking closely at how this is done. Water from the low pressure heaters is fed to the deareator. The deareator has two sections, the seperator section and the feedwater storeage section. The seperator section has a sparger or atomizer that breaks the feedwater into a mist, which then flows over trays that form sheets of water as it drains toward the storage section.

In the area of atomizer, live steam (pegging steam) is supplied. Pegging steam is sometimes called "equalization steam". This heats the water ever so slightly, as necessary to achieve saturation conditions for the pressure inside the deaerator. Water enters this section from the discharge of the condensate pumps at high pressure and is atomized in an area that is vented to the atmosphere. Mixing of the water with steam, ever so slightly raising the temperature and venting to atmosphere improves the release of the dissolved gases from the water. Note also that the slightly elevated temperature gases that rise to the top of the sparger section will due to the slightly higher than atomspheric pressure travel up the vent pipe to atmosphere.

Thus Deareator Pegging is the supply of an external steam supply to improve the removal of disolved gases from the feedwater, thus controlling boiler corrosion and reduction of fouling of heat transfer surfaces.