What are the common problems in boiler feedwater system?
When treating boiler feed water (the combination of boiler makeup and condensate return water), several issues can arise that cause boiler scaling, corrosion, fouling, and system failure.
What should be the temperature of feed water?
The temperature of the feedwater tank should be maintained between 185 and 195°F (85 and 90°C) to reduce the amount of oxygen in the water. By increasing the temperature and reducing the oxygen content, you can greatly reduce your sulfite or oxygen scavenger requirements.
How does a deaerator tank work?
The deaerator consists of a deaeration section, a storage tank, and a vent. In the deaeration section, steam bubbles through the water, both heating and agitating it. Steam is cooled by incoming water and condensed at the vent condenser. Noncondensable gases and some steam are released through the vent.
How feed water is treated and why it is required to be treated?
Boiler water must be treated in order to be proficient in producing steam. Boiler water is treated to prevent scaling, corrosion, foaming, and priming. Chemicals are put into boiler water through the chemical feed tank to keep the water within chemical range. These chemicals are mostly oxygen scavengers and phosphates.
What is meant by feed water?
noun. water to be supplied to a boiler from a tank or condenser for conversion into steam.
How do you control deaerator levels?
Maintaining correct level in the deaerator is very important when ensuring high quality feedwater. The deaerator level control valve needs to be operated with high rangeability and protection from cavitation at low flows.
Why do deaerator boilers feed water?
The purpose of a deaerator is to reduce dissolved gases, particularly oxygen, to a low level and improve a plant’s thermal efficiency by raising the water temperature. In addition, deaerators provide feedwater storage and proper suction conditions for boiler feedwater pumps.
What is the necessity of feed water treatment?
Feedwater treatment is a pre-water treatment process to control deposition, eradicate impurities and prevent corrosion within a boiler system. In a boiler system, water is transformed into steam and expands by as much as 1000 times as it passes through steam pipes at rates of 100km/hr.
How is a feedwater tank different from a deaerator?
Feedwater tanks are heated storage tanks that, unlike deaerators, don’t have a specific deaerating section and operate at atmospheric pressure. In addition to being a feedwater reservoir, these tanks also act as condensate receivers, cold water make up locations, and as a point for chemical injection.
What is the common failure mecahnism for a deaerator tank?
They generally consist of a water storage section and a deaerating/heating section. These tanks are typically made of welded carbon steel, and the residual stress of the welds coupled with the mechanical stress of operation makes them susceptible to weld cracking. Left undetected, these weld cracks can lead to catastrophic failures.
How is the deaeration of boiler feedwater done?
In order to deaerate the boiler feedwater, water is sprayed into a steam atmosphere. This heats the water to within a few degrees of the temperature of the saturated steam.
Why is my feedwater tank not making enough water?
On/Off make up control can also cause issues. If the make up rate is too great when the feedwater tank calls for water, the feedwater temperature can lower faster than the steam can raise it. The oxygen scavenger residual in the tank could also be completely consumed as a result.