Learning Boiler Blowdown Control

Water passing into the boiler must be treated with chemicals in order to protect the metals from corrosion. These chemicals enter the boiler along with the feedwater that has been cleaned, and help not only to purify water, but also to maintain a high quality of steam within the boiler. Once the water has been treated, these chemicals must also be taken out of the water as they can leave stains, corrosion, scale and foaming. Maintaining a chemical balance is therefore performed through a process known as boiler blowdown control.

Understanding Boiler Blowdown Control

This process is vital to keeping your boiler in good condition, and understanding how it works can help you to monitor the situation inside your boiler, and give you early warning of any changes. Blowdown control takes water from below the surface of the water in the boiler, and is often a "dirty" color, with sediment and particles in the drawn-off water. You should know before you begin any blowdown process that the amount of chemicals removed during the process has to be roughly the same as the amount that enter through feedwater. Too little blowdown can cause the harm described above, but too much can also affect the efficiency of the boiler, and may cost you money through heat loss. Therefore, a good balance has to be maintained between releasing the chemicals and keeping the steam within the boiler.

The Process of Boiler Blowdown Control

Boiler blowdown control involves triggering the blowdown mechanism using a valve. This valve can be found on the side of the boiler drum. Once you have found the pressure valve, start releasing the boiler water. Most valves on up-to-date boilers are fully automated, so all that needs to be done is to begin the blowdown sequence, but older boilers may have a more complicated format and should not be handled by amateurs. In order to calculate how much blowdown you have extracted, you should calculate the amount of water taken by the total quantity of feedwater within the boiler, and then times by 100. This will give you the percentage of water you have taken using blowdown.

Extracting Blowdown Control Water

The amount of water extracted from the boiler needs to be calculated according to the quality of boiler that you have. A high-quality boiler with good feedwater should only have a small percentage taken (less than 1%), while an older boiler with poorer standards in feedwater can have as much as 20% taken at one time. For a soft water, the percentage can be calculated by calculating 100, times blowdown quantity, divided by feedwater quantity, which equals the percentage of blowdown control water taken.

You can also add a material to the feedwater being taken into the boiler to calculate how much feedwater you are actually taking in, as the percentage of substance, such as chloride, appearing in the blowdown will give you a general estimate of the ratio between total water in the boiler and the amount being drawn off. Using a percentage method will help you to save money on your fuel bills, and keep the boiler functioning well.