To ensure your boiler is operating with the highest efficiency, you will need a boiler water treatment plan. This program can’t be established without understanding feedwater setups, and a key factor in understanding them is the impact of deaerator systems. Through these pressurized vessels, a process both preheats and removes the oxygen from the water, limiting corrosion and other detrimental activities to boiler performance. The feedwater tanks heat and store the water, which can be problematic as these operate at atmospheric pressure and don’t contain a deaerating section. A feedwater tank needs to be designed so that it reduces oxygen scavenging and reduces thermal shock. Here are two primary design issues that can occur in a feedwater tank.
1. Poorly Heated Feedwater
The boiled feedwater needs to be heated before it enters the boiler in order to prevent thermal shock. Heating also removes oxygen from the water. Usually, a steam sparger is inside the tank which heats it through steam from the boiler. If you increase the temperature and reduce the oxygen, you reduce the oxygen scavenger requirements as well as the sulfite level. Having an adequate heating supply is the first step in making sure your feedwater is being thoroughly heated.
2. Wrong Cold Water Design
There is a lot of oxygen in the cold water that enters the feedwater tank, and how the make up is fed and where it in the tank it is fed can impact how easy it is for oxygen to dissolve. The make up should be fed between 3-6 inches below the water line, and through a sparger slowly and continuously. Cold water is more dense than heated, and it can sink to the bottom of the tank and head more quickly into the boiler.
Keeping your boiler system in good working condition starts with the way your feedwater tank is designed. Look for ways to keep the water evenly heated and slowly to protect the integrity of the system.