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  • Writer's pictureSB Building Solutions LLC

DE-AERATOR Tank Vs. Feed-Water Tank

Updated: Dec 30, 2021



The temperature and oxygen level of your feed water is essential to your boiler. Both must be controlled to maintain optimal operational efficiency. To achieve prime performance you can control both the temperature and oxygen level of the feed water by using a DA tank (dearrator). While a dearrator tank and a feed water tank look some what the same and both hold feed water, The feed water tank can only control the temperature of the feed water. One of the design features that limits a feed-water tank is the vent pipe found on top of the tank that is open to the atmosphere. This open vent line limits the maximum water temperature inside a feed water tank to 212 degrees. On the other hand the deaerator is designed to hold water inside a pressurized vessel. Allowing the feed water to be held at temperatures up to 225 degrees. Many people make the mistake of thinking they are the same type of feed water system. While the deaerator tank will cost more up front the ROI for the DA tank will be seen in fuel savings and water treatment savings within the first couple of years. The design concept behind the DA tank is fairly simple. The DA tank is designed to store and treat the feed-water prior to entering the boiler hence;

  • Preventing boiler corrosion by reducing the level of oxygen in the fresh water being introduced to the DA tank

  • The use of a DA tank will also avoid thermal shock damage to your boilers and pumps. This type of damage is avoided by preheating the feed water before it is sent to the pumps and then onto the boiler.

  • The preheating of the feed water water also provides a savings in fuel cost. The fuel savings comes from the preheated feed water needing less BTU’s before steam is produced

While a plain feed water tank is cheaper to built and install the amount of preventive maintenance you will need to conduct every month will be increased. The level of scale build up and the risk of thermal shock will also be increased. As a professional in facility maintenance and boiler plant operations I always recommend to utilize a deaerator tank over a plain feed water tank. DA tanks are known for their consistency and reliability. Since a deaerator tank will remove most of the oxygen before the feedwater even enters your boiler system. The change of contamination and scale build up is reduced drastically. Plus the energy savings provided by the DA tank will be in place for years to come. Even if the DA tank was to fill with 100% oxygen rich fresh water, the DA tank would attempt to remove most of the oxygen and preheat the fresh water avoiding a case of thermal shock to the boiler and pumps.


Operational Differences


  • FEED-WATER TANK =A feedwater tank is open to the atmosphere and holds makeup water at temperatures ideal for the boiler system.


  • DEAERATOR TANK = A deaerator holds water inside a pressurized vessel. The purpose of a deaerator is to remove excess oxygen from makeup water. By boiling the make up water at a temperature higher then 212 F


Operating Temperatures


  • FEED-WATER TANK= Holds water at temperatures between 155°F and 185°F.


  • DEAERATOR TANK = Holds water under pressure at a steady temperature of 225°F


Oxygen Levels


  • FEED-WATER TANK = Oxygen levels average 5-10 parts per million (ppm). A feedwater tank sends water with high levels of oxygen into the boiler. Water is treated with chemicals inside the boiler to remove oxygen.


  • DEAERATOR TANK = Oxygen levels average 5 parts per billion (ppb) or lower.


Maintenance


  • FEED-WATER TANK=A higher degree of preventive maintenance and monitoring is required to avoid water treatment related issues.


  • DEAERATOR TANK = Once the deaerator is installed and setup properly, only regular scheduled maintenance of the equipment is necessary.


  • FEED-WATER TANK=If the feedwater tank empties and needs to pull cold city water to fill tank. The cold water could cause thermal shock, damaging tubes and causing boiler leaks.


  • DEAERATOR TANK = The higher temperature achieved by the deaerator alleviates the risk of thermal shock in instances when large amounts of fresh cold water needs to be used .


Water Treatment


  • FEED-WATER TANK=If the chemical feed is notworking properly and fails to remove oxygen, your boiler could very quickly build scale and corrosion which will cause a significant amount of damage to your boiler and boiler related equipment.


  • DEAERATOR TANK = The higher water temperature will also remove most of the oxygen before the feed water water enters Your boiler, providing added protection


Lifetime Operating Costs


  • FEED-WATER TANK=The initial investment for a feed water tank will be lower than a deaerator because you are purchasing a empty steel container as opposed to DA tanks interior steam coil and related control system.


  • DEAERATOR TANK = Deaerators will cost more upfront. The higher upfront cost is caused by the increased cost of the equipment, installation, certification, and training


  • FEED-WATER TANK=Chemical treatment will be substantially higher than a deaerator because all the oxygen in your feed water is being removed through the use water treatment chemicals inside your boiler.


  • DEAERATOR TANK = Additional savings will be seen in reduced scheduled maintenance and the use of less water treatment chemicals

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